News Collection | Dexter Research Center

How Is Spectral Sensitivity Selected in Infrared Temperature Sensors?

November 4, 2025

Non-contact infrared temperature measurement is a foundational technology across industries, from industrial process control and aerospace systems to medical diagnostics and consumer devices. By detecting the infrared (IR) radiation naturally emitted by objects, these sensors can accurately determine temperature without physical contact.

At the heart of this technique lies spectral sensitivity; the specific range of wavelengths that a sensor responds to. The choice of this wavelength band has a major influence on measurement accuracy, emissivity correction, and resistance to environmental interference. At Dexter Research, our thermopile detectors feature a broad, flat spectral response, offering the flexibility to tailor sensitivity precisely to each application through custom optical filters and window materials.

Basics of Spectral Selection in IR Sensors

All objects above absolute zero emit electromagnetic radiation according to blackbody radiation principles. Wien’s law tells us that as temperature increases, the peak emission wavelength shifts to shorter values. For example, a surface at room temperature (~300 K) emits most strongly around 10 μm, while molten metal at 1200 °C peaks near 2–3 μm.

This relationship forms the foundation for spectral selection. A broadband detector captures a wide range of wavelengths, generating a stronger overall signal. However, it may also collect unwanted background radiation or emissions from the environment. In contrast, a narrowband detector — typically achieved through an optical filter — limits detection to a specific wavelength range, improving selectivity but reducing total signal strength.

Designers must balance these trade-offs between signal strength and spectral purity to ensure reliable temperature readings under real-world conditions.

Thermopile Detectors and Our Approach

Our thermopile detectors stand out for their flat spectral absorption extending from the ultraviolet through the far infrared. This means the detector itself is largely neutral to wavelength; instead, the filter or window defines the effective spectral band.

This characteristic gives system designers exceptional freedom. By selecting an appropriate optical bandpass filter or window material, the sensor’s spectral sensitivity can be finely tuned to the target and environment. For instance:

8–14 μm band – ideal for industrial surface temperature measurement, as it matches the emission peak of most materials near ambient or moderate temperatures.
3–5 μm band – optimal for measuring hot metals or ceramics at elevated temperatures, where shorter wavelengths carry more radiative energy.
Shorter wavelengths (1–3 μm) – useful in specialized cases, such as when glass or atmospheric gases interfere in the longer IR bands.

Key Criteria When Selecting Spectral Sensitivity

Target Emissivity and Material

Emissivity — how efficiently a surface emits IR radiation — varies by wavelength. Some coatings, metals, and transparent materials behave differently across the spectrum. Selecting a spectral band that aligns with the material’s emissivity curve ensures accurate readings.

Ambient and Background Interference

Atmospheric gases, furnace windows, and background sources can distort readings if they emit or absorb in the same spectral band. Choosing a wavelength range outside these absorption peaks (for instance, avoiding water vapor bands) minimizes interference.

Window and Optics Transmission

Every optical element in the measurement path affects spectral transmission. The detector window, protective optics, and filters must all pass the chosen band efficiently. (We’ll explore window materials in more detail in an upcoming article.)

Signal-to-Noise and Response Time

A narrow spectral band limits total energy reaching the detector, which may lower signal strength and slow response. Our high-responsivity thermopile designs help maintain excellent signal-to-noise performance even with narrower filters.

Example: Measuring Molten Steel

Consider non-contact temperature measurement of molten steel at approximately 1200 °C. The peak emission occurs around 2–3 μm. Engineers might select a 1.6–3 μm or 3–5 μm band to capture strong emitted energy while avoiding ambient reflections. A sapphire or chalcogenide window provides the needed transmission, and a thermopile detector equipped with the appropriate filter delivers stable, accurate readings.

The process includes selecting the filter, calibrating emissivity, and verifying linearity — steps that we support through our engineering and applications expertise.

Because our thermopile detectors have a broad native spectral response, the customization of bandpass filters, windows, and packaging becomes a powerful design tool. Our in-house control of these parameters allows us to deliver detectors tailored to the exact needs of each infrared temperature measurement system.

Whether you require a specific optical filter, window material, or aperture size, we provide a range of standard and custom options to achieve optimal performance. This flexibility helps design engineers make the best trade-offs between sensitivity, selectivity, and environmental resilience.

Looking for Thermal Measurement Solutions?

Selecting the right spectral sensitivity is critical to achieving accurate, stable, and interference-free infrared temperature measurements. Starting with a detector that has a broad, uniform response and then tailoring the optical filter and window allows engineers to fine-tune performance for their specific application.

If you’re developing a non-contact infrared thermometer or thermal measurement system, our applications team can help you identify the ideal wavelength band, filter, and packaging configuration.

Contact Dexter Research Center today to discuss your infrared temperature sensing requirements and discover how spectral customization can elevate your system performance.

Minimizing Ambient Temperature Risks with Thermally-Compensated NDIR

October 27, 2025

Non-dispersive infrared (NDIR) gas sensors are a cornerstone of modern gas detection and monitoring systems. They are widely used in industrial safety, environmental monitoring, and HVAC control applications. However, one persistent challenge in NDIR systems is ambient temperature variation. Changes in ambient temperature can alter detector responsivity, source output, and gas absorption behavior, leading to measurement drift and calibration instability.

At Dexter Research, we address these challenges by combining high-performance thermopile detectors with advanced thermal compensation techniques to minimize the risks associated with ambient temperature fluctuations.

Overview of NDIR Sensing and Ambient Temperature Sensitivity

NDIR sensors detect specific gases by measuring how much infrared (IR) light is absorbed as it passes through a gas sample. The basic setup includes:

An infrared source that emits broadband IR radiation.
A gas sample cell, where the target gas absorbs radiation at characteristic wavelengths.
A narrow bandpass filter that isolates the absorption band of interest.
A thermopile detector, which converts the remaining IR energy into an electrical signal.

Ambient temperature fluctuations influence several of these components:

The IR source intensity changes with temperature.
The detector responsivity varies as thermoelectric materials and junctions warm or cool.
The gas cell density and absorption characteristics shift with temperature.

These effects can lead to output drift, requiring frequent recalibration if not properly managed. Effective temperature compensation, whether through hardware design or software algorithms, is essential for stable and accurate operation.

Thermally-Compensated Detector Design

Our thermally-compensated thermopile detectors are specifically engineered to reduce sensitivity to ambient changes. Models like the T34 compensated thin-film thermopile incorporate internal elements that counteract the effects of sudden temperature shifts on the detector package.

Key design features include:

A blinded compensating element or dual thermopile arrangement that generates a reference signal proportional to the ambient temperature change.
Packaging isolation to reduce thermal conduction between the sensing junctions and the external environment.
An integrated thermistor or reference resistor that provides a direct measure of detector package temperature for electronic correction.

Together, these features help stabilize the detector output even when the case temperature changes rapidly, maintaining consistent responsivity and minimizing zero offset drift.

Integration into NDIR Systems

Maintaining thermal stability at the detector stage is critical in NDIR systems. The detector must operate with a well-defined cold junction temperature, and any drift in that baseline directly affects measurement accuracy.

By using our thermally-compensated thermopiles, designers can significantly reduce temperature-related errors across typical ambient ranges (e.g., 10–40 °C). This compensation ensures that output variations due to ambient changes are minimized without requiring frequent recalibration.

Here’s a theoretical example: In a foundry gas analyzer where ambient conditions can swing dramatically, integrating a compensated thermopile and a dual-channel reference path (sample + reference) allows the system to subtract common-mode drift and maintain stability. The result is longer calibration intervals and more reliable gas concentration readings.

Best Practices for Minimizing Ambient Temperature Risk

To achieve the best results in NDIR systems, consider these proven techniques:

Stabilize the Detector Environment: Use insulation or controlled enclosures to minimize rapid temperature changes near the detector.
Implement Dual-Channel Compensation: Employ a reference path (zero gas channel) to automatically correct for temperature and source drift.
Apply Software Compensation Algorithms: Modern NDIR designs use calibration models to adjust for the temperature coefficient of responsivity (TCR). Our detectors typically exhibit low TCR values (e.g., −0.04%/°C), simplifying software correction.
Avoid Local Thermal Disturbances: Position sensors away from heat sources, direct sunlight, or cooling airflow to prevent transient drift.
Select Detectors with Low Intrinsic Drift: Choosing a thermally-compensated thermopile ensures the system baseline remains stable, even under wide environmental temperature swings.

Why Choose Dexter Research for NDIR Detector Front-Ends

With decades of experience in infrared thermopile design, Dexter Research offers detectors optimized for NDIR gas analysis and temperature stability. Our portfolio includes:

Low-TCR thermopile detectors for stable output.
Thermally-compensated models for robust performance across wide ambient ranges.
Custom packaging options to enhance thermal isolation and mechanical protection.

This combination of materials science, packaging, and design expertise reduces the calibration burden on system engineers and ensures more consistent long-term performance. Our detectors are trusted in applications from industrial emission monitoring to indoor air quality control and automotive exhaust sensing.

Interested in Thermally-Compensated NDIR?

Ambient temperature drift remains one of the biggest challenges in NDIR gas sensing, but it can be effectively mitigated through smart detector design and integration strategies. Using thermally-compensated thermopile detectors from Dexter Research significantly improves stability, reduces drift, and extends calibration intervals.

For high-accuracy gas measurement systems, collaborating early with your detector supplier ensures a robust, low-maintenance design.

Contact us today to discuss your NDIR front-end requirements — including thermopile selection, packaging, and compensation strategies tailored to your operating environment.

What Role Do Window Materials Play in IR Temperature Measurement?

October 23, 2025

In non-contact IR temperature measurement, infrared radiation from a target object often passes through a protective window before reaching the detector. This window can be part of a furnace door, industrial viewport, vacuum chamber, or sealed instrument housing. While its primary purpose is protection, the window plays a crucial optical role: its material, coating, thickness, temperature, and cleanliness all affect measurement accuracy.

At Dexter Research, we recognize that a detector is only as good as its optical path. In this article, we examine how window materials influence performance in infrared temperature sensing and how to select the right one for your application.

Fundamentals of IR Windows

An IR window is a transparent medium that allows infrared radiation to pass through while protecting the detector or optical components from harsh environments. It may also act as an optical filter, shaping the spectral band that reaches the detector.

Key optical parameters include:

Spectral transmittance: How efficiently the window passes IR radiation at each wavelength.
Absorption and reflection: Internal losses and surface reflections reduce total signal.
Emittance and scattering: The window itself can emit or scatter radiation, especially at high temperatures.
Temperature dependence: Many materials change transmission characteristics as they heat up.

Mechanical and thermal properties also matter: thermal expansion, warping, and surface contamination can degrade both optical and structural performance.

Common Window Materials and Their IR Characteristics

For the most common 8–14 μm infrared thermometry band, several materials are widely used:

Zinc Selenide (ZnSe) – High transmission across 4–14 μm (~72% per Calex data), durable, and resistant to thermal shock. Popular for industrial and furnace-view applications.
Germanium (Ge) – Excellent 2–14 μm transmission, but heavier and more expensive. Performs well at elevated temperatures.
Silicon (Si) – Useful for shorter wavelengths (1–5 μm); transparent in near-IR but opaque beyond ~8 μm.
Sapphire (Al2O3) – Very strong mechanically, transmits up to ~5 μm, ideal for high-temperature and abrasive environments.
Chalcogenide glasses – Cost-effective option for 8–14 μm band, but with lower durability and temperature limits.

Other materials may be chosen for specialized spectral ranges (e.g., 3–5 μm for hot metal measurement). Anti-reflection and protective coatings can enhance transmission and extend window life, especially in harsh or dusty environments.

Impacts on Measurement Accuracy

Even the best IR window affects measurement results in several ways:

Reduced Signal Strength

No window transmits 100% of radiation. Lower transmission means less signal reaching the detector, requiring emissivity compensation or calibration correction. The effective emissivity can be calculated as:

Effective emissivity = object emissivity × window transmission

Window Emission and Absorption

As windows absorb IR energy, they may heat up and emit their own radiation, adding bias to temperature readings.

Spectral Mismatch

If the window’s transmission band does not perfectly overlap with the detector’s or filter’s spectral response, certain wavelengths may be attenuated, reducing accuracy.

Temperature Gradient and Contamination

Hot windows develop internal temperature gradients that distort readings. Additionally, soot, oxidation, or condensation can lower transmission significantly, particularly in furnace or combustion environments.

Proper window heating, purging, or periodic cleaning can minimize these effects.

Selecting and Specifying Windows for IR Thermometry

Choosing the correct window material involves balancing optical, thermal, and mechanical factors:

Match the spectral band: Ensure the window transmits effectively across the sensor’s measurement band.
Account for operating temperature: Choose materials that remain stable under expected heat loads.
Consider environment: Evaluate whether the window faces vacuum, overpressure, corrosive gases, or mechanical vibration.
Plan for maintenance: Select materials and coatings that resist fouling and are easy to clean or replace.
Apply emissivity correction: Adjust the sensor’s emissivity setting using the product of object emissivity and window transmission.

Example: Product and Application Synergy

Imagine a thermopile detector mounted behind a ZnSe window monitoring a furnace interior. The 8–14 μm band is ideal for moderate-to-high-temperature surfaces, while ZnSe offers good transmission and resistance to thermal stress. We supply the detector, optical filter, and aperture matched to that band, ensuring reliable readings.

In another case, a cost-sensitive HVAC application may use a polymer protective window. While less expensive, the polymer absorbs more IR energy, requiring calibration adjustments and lower operating temperatures. We support both configurations, tailoring filters and packaging to compensate for window effects.

By controlling detector design, filters, and window selection in-house, we deliver integrated optical paths optimized for precise IR temperature measurement.

Looking for IR Temperature Measurement Solutions?

Window materials play a critical yet often underestimated role in IR temperature measurement. They define how much infrared radiation reaches the detector, influence calibration, and affect long-term stability in demanding environments.

For best results, designers should consider the entire optical path — from target to detector — as a unified system. At Dexter Research, we help customers specify detectors, filters, windows, and apertures that work together seamlessly.

Contact our applications team to discuss your infrared window material needs and learn how to optimize your measurement system for accuracy, durability, and performance.

How Are Thin-Film Thermopiles Used in MicroSat Satellites?

October 15, 2025

As the small satellite (MicroSat) market continues to grow, mission designers face a constant challenge: achieving precise measurement and control in compact, low-power systems. One of the most critical functions onboard MicroSats is thermal and attitude sensing, where thin-film thermopile detectors play an increasingly important role.

These detectors serve as the foundation for Earth horizon sensors, non-contact thermal monitors, and other key subsystems that help satellites orient themselves and maintain stable operation in orbit. At Dexter Research, we offer high-performance thin-film thermopile detectors optimized for aerospace, horizon sensing, and thermal instrumentation in the harsh environment of space.

Thin-Film Thermopiles: What Are They?

A thermopile detector consists of a series of thermocouples connected in series or parallel, with alternating hot and cold junctions. When infrared radiation heats the absorber on the hot junctions, a voltage is generated via the Seebeck effect — proportional to the temperature difference between the junctions.

In thin-film thermopiles, these thermocouple structures are fabricated on ultra-thin membranes, typically using bismuth-antimony (Bi-Sb) or similar materials. Compared to silicon-based thermopiles, these thin-film variants offer:

Higher signal-to-noise ratio (SNR) for detecting faint IR sources.
Larger active area, improving energy collection.
Thinner membrane construction, enhancing sensitivity.
Slightly slower response time, which is acceptable in many satellite applications.

These characteristics make thin-film thermopiles ideal for aerospace applications, where they must detect small infrared gradients, such as distinguishing the Earth’s horizon from the cold background of deep space, while maintaining mechanical ruggedness and long-term stability.

Application in MicroSatellites

MicroSats rely on thermopile detectors for several critical sensing functions:

1. Horizon Sensing

In Earth-observing or navigation satellites, horizon sensors use thermopile arrays to detect the transition between Earth’s warm infrared emission and the cold background of space. A common configuration uses quad-thermopile sensors: four detectors arranged in quadrants that view slightly different directions. By comparing the IR signal from each quadrant, the system determines the satellite’s nadir vector and attitude.

2. Thermal Health Monitoring

Thin-film thermopiles can also serve as non-contact temperature sensors for monitoring satellite components. By viewing structural surfaces or equipment radiating heat, they help detect early signs of overheating or thermal imbalance without the need for contact thermistors or RTDs.

3. Solar and Environmental Sensing

Thermopiles can measure solar IR flux or Earth albedo, supporting thermal modeling and energy management subsystems.

The key benefits of thin-film thermopiles in these roles include compact size, low power consumption, passive operation (no cooling required), and excellent radiation tolerance.

Design Considerations for Space Use

Using thermopiles in orbit introduces several design challenges that we address through careful engineering:

Radiation and Vacuum Compatibility: Materials must be radiation-tolerant and fully vacuum-qualified. Our hermetic packaging ensures long-term reliability.
Temperature Extremes: Satellite instruments experience large temperature swings; our thermopiles feature low temperature coefficients for stable output.
Outgassing Resistance: Aerospace-approved adhesives and coatings prevent contamination of optical surfaces.
Time Constant: Although thin-film thermopiles have a slightly slower response than MEMS types, this aligns well with satellite attitude determination, where rapid transients are rare.
Calibration Stability: Our low-drift designs reduce the need for frequent recalibration, ensuring consistent sensor performance throughout multi-year missions.
Optical Path Considerations: Horizon sensors typically operate in the 8–14 μm infrared band, where Earth’s thermal emission is strongest. We supply compatible optical windows and filters that withstand thermal cycling and maintain high transmission.

Finding a Partner for Space and MicroSat IR Sensing

Dexter Research has a longstanding reputation in infrared sensing for aerospace. Our product portfolio includes both thin-film and silicon thermopiles, available in multiple package sizes and configurations. Key differentiators include:

Customizable optical filters, windows, and apertures for mission-specific spectral bands.
Hermetically sealed packages for vacuum environments.
High manufacturing quality — each detector 100% tested for consistency and reliability.

Our experience supporting horizon sensors, environmental monitors, and thermal control systems makes us a trusted partner for satellite developers seeking proven, space-qualified infrared detectors.

Looking for MicroSat Solutions?

Thin-film thermopile detectors are ideally suited for MicroSat and small satellite missions requiring precise, passive infrared sensing. Their combination of sensitivity, reliability, and low power consumption enables compact horizon sensors and thermal instrumentation that meet the stringent demands of space environments.

For satellite OEMs and integrators, partnering with Dexter Research Center ensures access to customizable, aerospace-grade thermopile solutions backed by decades of IR expertise.

Contact our aerospace applications team to discuss thin-film thermopile detector options for your MicroSat project and discover how our detectors can enhance your next-generation space system.

How Accurate Are Tympanic Ear Thermometers? A Look at Reliability and Use

September 8, 2025

Temperature measurement is a cornerstone of clinical diagnosis and patient monitoring. In both pediatric and general medical settings, tympanic ear thermometers have become widely used for their speed, comfort, and non-invasive design. These infrared-based devices detect thermal radiation from the tympanic membrane (eardrum), offering a fast and hygienic way to assess core body temperature. Dexter Research, a leader in thermal detection technology, provides the precision infrared sensors that underpin many of these instruments.

How Tympanic Thermometers Work

Tympanic thermometers function by detecting the infrared radiation naturally emitted from the eardrum, which shares a blood supply with the hypothalamus—the body’s temperature regulation center. The sensor converts this infrared signal into a temperature reading within seconds.

Key benefits include:

Non-invasive measurement: Ideal for children, elderly, or uncooperative patients.
Speed: Provides near-instantaneous readings.
Hygiene: Disposable probe covers and minimal skin contact reduce contamination risks.

These advantages make tympanic thermometers especially practical in clinical workflows and busy care environments.

Evidence Supporting Accuracy

Multiple studies have evaluated the accuracy of tympanic thermometers relative to traditional mercury and axillary thermometers:

Comparable to mercury thermometers: Clinical trials show that when used correctly, tympanic thermometers provide readings equivalent to mercury-in-glass thermometers.
High diagnostic accuracy: A meta-analysis of next-generation tympanic devices in pediatric populations demonstrated reliable fever detection, supporting their use in routine screenings.

Comparing Measurement Sites

It is normal for body temperature readings to vary slightly depending on the measurement location:

Ear vs. oral: Tympanic temperatures typically read 0.3°C to 0.6°C (0.5°F to 1°F) higher than oral readings.
Ear vs. rectal: Rectal readings are often considered the gold standard for core temperature but are invasive and less practical in many settings,

Despite these differences, tympanic thermometers offer sufficient accuracy for clinical decision-making, especially in detecting febrile states.

Factors That Influence Accuracy

Like all medical instruments, tympanic thermometers require proper usage for optimal performance:

Technique matters: Inserting the probe correctly and aligning it with the eardrum is critical.
Obstructions: Earwax, infections, or physical blockages can skew results.
Consistency: Repeated measurements should be taken from the same ear for reliable comparisons.

Manufacturers provide detailed guidance on usage—following these instructions is essential to obtain dependable readings.

When to Use Tympanic Thermometers

Tympanic thermometers are particularly well-suited for:

Pediatric care: Quick, non-invasive measurement is beneficial for infants and toddlers.
Emergency screenings: Rapid fever assessment in triage and public health settings.
Routine checks: Ideal for ambulatory care or at-home use by caregivers.

However, alternative methods like rectal or temporal artery thermometers may be preferable in neonates or when the highest precision is required.

Dexter Research’s Role in Thermometry

Dexter Research supplies infrared detectors that power many tympanic thermometers. Known for high sensitivity and reliability, these components ensure fast and accurate temperature readings in medical-grade devices.

For healthcare manufacturers seeking custom thermal sensing solutions, Dexter Research offers a portfolio of specialty detectors optimized for human thermometry applications.

Developing Tympanic Ear Thermometers?

Tympanic ear thermometers are a fast, convenient, and reliable option for clinical temperature measurement when used correctly. They deliver readings comparable to traditional methods and are supported by a strong body of clinical evidence. By adhering to best practices and manufacturer guidelines, healthcare providers can trust tympanic thermometers as effective tools for fever screening and general patient monitoring. Dexter Research’s advanced infrared motion sensor units continue to support innovation in this essential area of care.

What Is a Radiometer Sensor?

August 28, 2025

Radiometer sensors are essential tools in modern science and industry. They provide a non-contact means of measuring radiant energy—especially infrared radiation—making them indispensable for tasks ranging from environmental monitoring to high-precision manufacturing. As experts in thermal detection, Dexter Research supplies radiometric sensors that deliver the sensitivity and accuracy needed across these diverse fields.

What Is a Radiometer Sensor?

A radiometer is a device that measures radiant flux—the total power of electromagnetic radiation—emitted by a surface or object. Unlike contact-based thermometers, radiometers detect infrared energy remotely and calculate an object’s temperature or energy output based on that data. This makes them particularly valuable when the target is too hot, dangerous, or inaccessible for direct contact.

The core function of a radiometer sensor is grounded in radiometry, the science of measuring electromagnetic radiation across a wide spectrum. While visible light is part of this spectrum, radiometers are capable of detecting much broader ranges, including the infrared and ultraviolet bands.

Radiometry vs. Photometry: A Key Distinction

Radiometry and photometry both involve the measurement of light, but they serve different purposes:

Radiometry quantifies all electromagnetic radiation, regardless of human perception. It uses units like radiant flux (watts) and spectral radiance.
Photometry, by contrast, is limited to visible light and is weighted by the human eye’s response. It uses terms like luminous flux (lumens).

This distinction is critical when choosing sensors for scientific, industrial, or safety applications, where accurate infrared detection—not human brightness perception—is the goal.

How Radiometer Sensors Work

Radiometer sensors measure energy by detecting infrared radiation and converting it into an electrical signal. Key technical factors include:

Field of View (FOV): The angular area the sensor observes. A narrower FOV targets specific objects, while a wider FOV collects radiation from larger areas.
Spectral Distribution: The range of wavelengths the sensor is sensitive to. Different materials emit radiation differently across spectra; matching sensor response to the application ensures accuracy.
Emissivity Correction: All surfaces emit IR energy at different efficiencies. Emissivity values must be factored into calculations to avoid skewed readings.
Unit Solid Angle and Calibration: Radiometers are calibrated using unit solid angles and often reference standard wavelengths, such as 450 nm, which is close to the peak sensitivity of the human eye.

Modern radiometers, like those using thermopile detectors from Dexter Research, are finely tuned to deliver reliable data across varying ambient conditions.

Applications of Radiometer Sensors

Radiometers serve a broad range of scientific and industrial roles:

Environmental Monitoring: Measuring land and sea surface temperatures, monitoring atmospheric energy balance.
Industrial Process Control: Monitoring the thermal output of machinery or products to ensure consistency and safety.
Scientific Research: Used in astrophysics, climatology, and remote sensing to measure radiation from celestial bodies or Earth systems.
Medical and Safety Devices: Non-contact thermometers and thermal imagers operate on radiometric principles.

Dexter Research’s 2M thermopile detectors and high-temperature sensors are well-suited for high-sensitivity applications, offering precision even in demanding thermal environments.

Selecting the Right Radiometer Sensor

When choosing a radiometer, consider the following factors:

Field of View: Determine the spatial scope of the target area.
Spectral Range: Match the sensor’s sensitivity to the wavelength range relevant to the application.
Temperature Range: Choose sensors rated for the expected temperature extremes.
Calibration and Emissivity: Ensure the device supports emissivity correction and regular calibration routines.

Dexter Research’s sensor portfolio includes models optimized for specific spectral windows and customizable FOVs, enabling tailored solutions for diverse applications.

Interested in Radiometer Sensors?

Radiometer sensors are foundational to non-contact temperature and energy measurements across science, industry, and safety. By detecting infrared radiation with precision and speed, these instruments provide actionable insights without disturbing the target. With decades of expertise in thermopile technology, Dexter Research offers a wide array of radiometric detectors to meet the evolving needs of researchers, engineers, and system integrators.

Using Solar Detectors to Measure the Sun’s Total Broadband Radiation

Understanding and quantifying the sun’s total broadband radiation is essential for advancing solar energy, climate science, and photonics. The sun emits energy across a vast range of wavelengths, from ultraviolet (UV) through visible light and into the infrared (IR). Accurately capturing this radiation informs solar power design, atmospheric modeling, and the development of optical technologies. Dexter Research supports this effort with precision-engineered solar detectors that enable researchers and engineers to measure solar irradiance with high fidelity.

The Solar Radiation Spectrum

Solar radiation spans the entire electromagnetic spectrum, but most of the sun’s energy reaching Earth lies between 0.3 and 2.5 micrometers, covering UV, visible, and IR wavelengths. The term total broadband radiation refers to the sum of radiation across this full spectral range. Measuring this radiation comprehensively requires sensors that respond effectively across multiple wavelength bands.

It wasn’t until the late 1970s that scientists obtained the first measurements of total solar irradiance from space. These findings provided critical insight into Earth’s energy balance and highlighted the need for accurate ground- and satellite-based solar detectors.

Types of Solar Detectors

Two key types of instruments are commonly used to measure solar broadband radiation:

Pyranometers: Designed to measure total solar irradiance on a flat plane, pyranometers capture both direct sunlight and diffuse sky radiation. They are widely used in meteorological stations, solar farms, and atmospheric research.
Radiometers: Unlike pyranometers, radiometers often target specific wavelength bands. They are ideal for detailed spectral studies, space-based observations, and photonic research requiring selective measurement.

Both types rely on highly sensitive detectors, and Dexter Research’s thermopile-based solutions play a critical role in their performance.

Thermopile Detectors and the Seebeck Effect

At the core of many solar detectors is a thermopile detector. These devices use the Seebeck effect, where a voltage is generated in response to a temperature difference between junctions of dissimilar materials.

When solar radiation strikes the absorber surface of a thermopile, it raises the temperature relative to a cold junction. This temperature difference produces a voltage that is directly proportional to the absorbed energy. Thermopile detectors are well-suited for broadband applications because they respond uniformly to a wide range of wavelengths.

Dexter Research’s thermopile technology ensures high sensitivity, low noise, and long-term stability—critical features for continuous solar monitoring.

Measurement Techniques and Considerations

Solar detectors quantify irradiance, typically expressed in watts per square meter (W/m²). To ensure accurate readings, several factors must be managed:

Spectral Response: The detector must be calibrated to reflect the actual distribution of solar energy across wavelengths.
Calibration Standards: Instruments are calibrated against traceable standards to ensure data integrity over time.
Environmental Conditions: Factors such as tilt angle, cleanliness of the sensor window, and temperature can influence readings and must be controlled or compensated for.

High-quality detectors with broad spectral sensitivity and rigorous calibration provide the most reliable measurements.

Applications and Impact

Solar broadband measurement is foundational in many fields:

Solar Energy Systems: Assess solar resource availability, optimize panel alignment, and monitor performance over time.
Climate Science: Feed critical data into Earth system models to understand radiative forcing and global energy dynamics.
Photonics and Optics: Guide the design of coatings, filters, and lenses that interact with solar energy.
Agriculture: Support precision farming by correlating solar input with crop development.
Environmental Monitoring: Track changes in solar input that influence atmospheric chemistry and surface temperature.

Dexter Research Solutions

Dexter Research offers a range of solar detectors that support both broadband and selective spectral measurements. With options tailored to UV, visible, and IR detection, these sensors combine rugged construction with exceptional precision. Whether embedded in pyranometers, radiometers, or integrated systems, Dexter’s thermopile detectors provide consistent, accurate results in demanding field conditions.

Digital interface options and miniaturized formats further enhance usability across research, industrial, and energy applications.

Learn More About Solar Detectors

Capturing the full scope of the sun’s broadband radiation is critical for advancing renewable energy, climate research, and photonic innovation. By leveraging thermopile detectors and expertly calibrated instrumentation, solar detectors translate sunlight into actionable data. Dexter Research continues to support this mission with a portfolio of reliable, high-performance solutions designed for today’s solar measurement challenges.

How Does an NDIR CO₂ Sensor Work?

August 7, 2025

Carbon dioxide (CO₂) sensing plays a pivotal role in environmental monitoring, indoor air quality management, industrial process control, and greenhouse optimization. As concerns about air quality and climate resilience grow, the demand for accurate and continuous CO₂ monitoring intensifies. NDIR (non-dispersive infrared) technology has become the go-to method for detecting CO₂ due to its precision, longevity, and robustness. At the heart of many such sensors are thermopile detectors, including those engineered by Dexter Research.

Why Is CO₂ Hard to Measure?

CO₂ is invisible, odorless, and non-reactive under normal conditions, making it difficult to detect without specialized instruments. Traditional chemical and electrochemical methods can suffer from limited lifespans, cross-sensitivity to other gases, and slow response times. NDIR overcomes these challenges by targeting a specific infrared absorption band unique to CO₂.

The Principle of NDIR CO₂ Detection

NDIR sensors detect CO₂ by focusing on its strong infrared absorption band near 4.26 micrometers (µm). When IR light of this wavelength passes through a gas sample, CO₂ molecules absorb part of it. The amount of light absorbed is directly related to the gas concentration, governed by the Beer–Lambert law:

A = ε × c × l
Where:

A is absorbance
ε is the molar absorptivity of CO₂
c is the concentration
l is the path length of the IR beam

By measuring the intensity of transmitted light (I) and comparing it to the original intensity (I₀), the sensor calculates the absorbance and infers CO₂ concentration.

Sensor Architecture: Tailored for CO₂

NDIR CO₂ sensors include the following key components:

IR Source: Emits broadband infrared radiation.
Optical Filter: Precisely selects the 4.26 µm wavelength corresponding to CO₂ absorption.
Gas Cell or Waveguide: Directs the IR beam through the gas sample; folded or reflective waveguides can extend the optical path in a compact form.
Thermopile Detector: Converts transmitted IR radiation into an electrical signal.
Reference Channel: Measures a nearby non-absorbing wavelength to provide a stable baseline.

This configuration enables continuous, real-time detection with minimal interference from other gases.

Signal Processing and Calibration

Once the detector captures the IR signal, electronics calculate the absorbance and convert it into a concentration value using stored calibration curves. To ensure accuracy over time, NDIR CO₂ sensors often include:

Baseline Self-Calibration: Algorithms periodically recalibrate the sensor using the lowest CO₂ value observed over a defined interval.
Sealed Reference Cells: Provide a known standard for high-precision applications.
Temperature and Pressure Compensation: Adjust readings for environmental conditions that affect IR absorption.

The output is typically available as a digital (UART, I²C) or analog (4–20 mA) signal, making it easy to integrate with building automation or industrial systems.

Why NDIR for CO₂?

NDIR sensors offer distinct advantages:

High Selectivity: Tuned to CO₂’s unique absorption band.
Non-Consumptive: Does not alter or consume the sample gas.
Long-Term Stability: Resistant to drift and contamination.
Fast Response: Real-time monitoring with short lag time.
Low Maintenance: Minimal recalibration compared to chemical sensors.

In contrast, electrochemical and chemical sensors degrade over time, require frequent replacement, and may respond to similar gases.

Use Cases: Where NDIR CO₂ Sensors Excel

Application Area	Example Uses
Indoor Air Quality	Smart thermostats, ventilation control
Greenhouse Monitoring	CO₂ enrichment and control
Industrial Process Control	Safety and combustion efficiency
Building Automation	Demand-controlled ventilation (DCV) systems
Safety Alarms	Confined space CO₂ monitoring

The ability to provide real-time, reliable measurements makes NDIR CO₂ sensors a mainstay in smart infrastructure.

Emerging Innovations

Recent developments have enhanced the performance and usability of NDIR CO₂ sensors:

Miniaturized Waveguides: Deliver extended path lengths in smaller packages.
Digital Interfaces: UART and I²C simplify integration with microcontrollers and IoT platforms.
Low-Power Designs: Support long-life, battery-operated devices.
Smart Algorithms: Enable auto-calibration and real-time diagnostics.

These features are driving the adoption of NDIR CO₂ sensing in wearables, portable instruments, and smart home systems.

Looking for NDIR Sensors?

NDIR CO₂ sensors leverage selective infrared absorption to provide accurate, real-time monitoring of carbon dioxide levels. With tailored optical components, built-in reference channels, and advanced signal processing, they offer a robust solution for today’s air quality and safety needs. Dexter Research’s thermopile detectors are central to many of these systems, providing the performance and stability required across industries. As demand for precise gas sensing grows, NDIR remains the trusted standard for CO₂ detection.

Why Passive Infrared Is the Go-To Technology for Motion Sensor Units

July 3, 2025

Motion sensors are integral to modern automation, from lighting and HVAC control to security systems. Among the available technologies, passive infrared (PIR) sensors stand out for their simplicity, reliability, and efficiency. Dexter Research, a leader in infrared detection, has decades of experience engineering thermal sensing solutions that drive innovation in this field. In this post, we’ll explore why PIR sensors are ideally suited for motion detection and how they deliver both technical and user-centric benefits across a wide range of applications.

Understanding Passive Infrared Sensing

All objects emit thermal infrared radiation, with intensity proportional to their temperature. PIR sensors take advantage of this by detecting fluctuations in infrared energy caused by moving warm bodies — typically humans or animals — within a given scene.

The core of a PIR sensor includes two elements that respond to temperature changes. These elements are shielded beneath a Fresnel lens, which concentrates infrared energy onto the sensor. The dual-element setup ensures that minor ambient changes are ignored, while true movement — such as a person walking past — produces a differential signal that activates a response.

How PIR Motion Sensors Work

When a warm object moves across the sensor’s field of view, it causes a sequential change — one element sees a rise in IR, followed by the other. This sequence creates a differential signal that the sensor electronics interpret as motion.

Key components include:

Fresnel Lens: Creates distinct detection zones, shaping the field of view.
Low-Power Electronics: PIR sensors typically operate at microamp currents, making them ideal for battery-powered devices.

Why PIR Sensors Are Ideal for Motion Detection

Feature	Benefit
Works in light or dark	Detects thermal radiation, independent of ambient lighting
Differentiates humans from background	Sensitive to thermal signatures of living beings
Low energy consumption	Consumes microamps at idle, ideal for long-life batteries
Non-invasive and privacy-respecting	Senses motion without capturing images or personal data
Cost-effective and reliable	Affordable and proven across diverse industries
Versatile applications	Suitable for alarms, lighting, HVAC, automatic doors, dispensers, and more

This combination of low power draw, environmental robustness, and privacy preservation makes PIR the default choice for motion detection in both consumer and industrial settings.

Real-World Applications of PIR Motion Sensors

PIR technology is embedded in everyday systems including:

Security alarms that detect unauthorized movement
Lighting systems that activate only when needed
Thermostats that optimize energy use based on occupancy
Automatic doors and hygiene dispensers in commercial spaces
Smart home presence sensors, such as Dexter Research’s unit with a two-foot detection range for proximity applications

From building automation to bespoke embedded devices, PIR sensors provide scalable and adaptable solutions.

Deployment Considerations and Best Practices

To get the most out of a PIR sensor, designers should consider the following:

Field of View: Fresnel lenses create zones of high and low sensitivity. Selecting the right lens shape and orientation tailors detection to specific environments.
Minimizing False Alarms: Position sensors away from heat vents or rapidly changing temperature zones. Fine-tune sensitivity thresholds to avoid triggering from stationary heat sources.
System Integration: PIR sensors easily interface with microcontrollers and smart platforms, enabling event-driven automation for lights, alarms, and more.

Installation tips include mounting sensors at standard heights (typically 6–8 feet) and angling them to monitor expected motion paths effectively.

Interested in Motion Sensor Unit Solutions?

Passive infrared sensors strike the perfect balance of performance, efficiency, and discretion in motion detection. Their ability to function reliably across diverse lighting and environmental conditions, while consuming minimal power, makes them indispensable across industries. At Dexter Research, we continue to push the boundaries of thermal sensing — offering PIR solutions that are compact, customizable, and proven in real-world applications for motion sensor units.

Understanding key technologies in presence detection

November 26, 2024

When technology for presence detection is employed in a location, it’s done so knowing that it can add a robust level of security, lower energy waste, and deliver convenience to those who visit the space. Essentially, presence detection is applied to reveal if there is anyone in a certain environment. Presence detection tools are utilized in numerous applications, from identifying intruders that enter a home to patient observation. Let’s find out more about the different types of technologies available for presence detection.

Infrared Sensors

What are Infrared Sensors?

An infrared sensor is a device applied to undertake motion sensing, temperature measurements, and presence detection. These sensors can identify infrared radiation (IR), also known as heat energy, before transforming it into an electrical signal. It’s the quantification of this heat that allows the infrared sensor to understand if an individual is in a location.

How Do Infrared Sensors Operate?

Thermopiles are utilized within infrared sensors for transforming thermal energy into electrical energy. They’re made up of thermocouples that can help produce a voltage, which is based upon temperature variations. These thermocouples are connected either in parallel or series and work together to boost an output voltage.

Every object with a temperature over absolute zero will produce IR, in other words heat. This is something that the thermopile is sensitive to, absorbing it through a black-coated surface. The thermopile’s thermocouples contain a cold junction, which acts as a reference point. It also has a hot junction, which comes into contact with the IR that’s been absorbed. If differing temperatures are identified then a voltage is produced, this voltage increasing with higher temperature differences.

From there, the sensor is able to boost the voltage signal and process it, quantifying the differences in temperature between the environment and an object. These temperature-related insights are then used to deliver presence detection.

Benefits

Infrared sensors do not need to experience physical contact to be able to identify a presence. They operate passively, ergo they do not emit signals and are less intrusive. Moreover, they offer a quick response time and have an extensive operating range. They’re also privacy-friendly, since they only identify heat instead of visuals, and durable, as they do not have any moving parts and, thus, are less likely to experience wear.

Ultrasonic Sensors

What are Ultrasonic Sensors?

For those that need technology that does not necessitate visual contact to identify movement, ultrasonic sensors are the answer. Ultrasonic sensors are able to pinpoint people or objects within a space by using sound waves.

How Do Ultrasonic Sensors Operate?

These sensors release high-frequency sound waves, that are usually over 20 kHz, which will hit an object. The sound waves will then be sent back towards the sensor. Once they reach, the sensor will quantify the amount of time that was needed for their return to take place, utilizing this time to discover the distance required to reach the object. Its outcome will show whether a change has occurred in the location. The ability to continuously monitor reflections help the sensor to learn about any movement or presences.

Benefits

Ultrasonic sensors can work in various lighting conditions, including darkness. They also offer sensing capabilities that traverse through thin barriers, such as fabric. Additionally, physical interaction is not needed for ultrasonic sensors to recognize a presence, meaning it can be utilized with inaccessible areas.

Pressure and Weight Sensors

What are Pressure and Weight Sensors?

Pressure and weight sensors offer presence detection when they experience contact from an object or person. Some of examples of these sensors include:

Piezoelectric sensors: Produce an electric charge in relation to mechanical stress.
Load cells: Calculate the amount of weight that occurs on a surface and turns it into an electrical signal.
Capacitive pressure sensors: Deliver measurements of any alterations in capacitance that occur due to pressure on a material.

How do Pressure and Weight Sensors Operate?

Usually found in pads, mats, beds, and seats, pressure and weight sensors can understand any changes that occur when a surface experiences weight, force, or pressure. If this happens, the sensor produces a signal indicating additional processing is required to see if there’s an object in the vicinity. It does this to also learn about the object’s potential weight.

Benefits

These sensors offer excellent accuracy when identifying changes in pressure and weight, delivering reliability if utilized in a fixed location. They’re also non-intrusive, possessing the ability to function without being identified either audibly or visually.

Select a Key Technology In Presence Detection That Works For You

The right technology for presence detection can do wonders for your security. Therefore it’s important to think carefully about which device would be suitable for your application. If you’re still unsure about what type of motion detectors or presence detection tools could work for you, we would recommend that you take a look at our thermopile sensors. These can be applied to motion detectors and have excellent sensitivity and an extensive lifespan. Our sensors are devices that you can trust to help you take control of your security. Have a look at our products and learn more about what our technology can do.