Guarantee
This equipment is guaranteed against defects in materials and workmanship. This guarantee applies for twelve months from date of delivery. Campbell Scientific will repair or replace products which prove to be defective during the guarantee period provided they are returned prepaid. The guarantee will not apply to:
- Equipment which has been modified or altered in any way without the written permission of Campbell Scientific
- Batteries
- Any product which has been subjected to misuse, neglect, acts of God or damage in transit.
Campbell Scientific will return guaranteed equipment by surface carrier prepaid. Campbell Scientific will not reimburse the claimant for costs incurred in removing and/or reinstalling equipment. This guarantee and the Company's obligation thereunder is in lieu of all other guarantees, expressed or implied, including those of suitability and fitness for a particular purpose. Campbell Scientific is not liable for consequential damage.
Please inform Campbell Scientific before returning equipment and obtain a Repair Reference Number, whether the repair is under guarantee or not. Please state the faults as clearly as possible. If the product is out of the guarantee period, it should be accompanied by a purchase order. Quotations for repairs can be given on request. It is the policy of Campbell Scientific to protect the health of its employees and provide a safe working environment. In support of this policy, a "Declaration of Hazardous Material and Decontamination" form will be issued for completion.
When returning equipment, the Repair Reference Number must be clearly marked on the outside of the package. Complete the "Declaration of Hazardous Material and Decontamination" form and ensure a completed copy is returned with your goods. Campbell Scientific Ltd reserves the right to return goods at the customers' expense if a copy of this form is not included. Your repair may not be processed without it.
Note that goods sent air freight are subject to Customs clearance fees which Campbell Scientific will charge to customers. In many cases, these charges are greater than the cost of the repair.
Campbell Scientific Ltd,
Campbell Park, 80 Hathern Road,
Shepshed, Loughborough, LE12 9GX, UK
Tel: +44 (0) 1509 601141
Fax: +44 (0) 1509 601091
Email: support@campbellsci.co.uk
Website: www.campbellsci.co.uk
PLEASE READ FIRST
About this manual
This manual was originally produced by Campbell Scientific Inc. primarily for the North American market. Some spellings, weights, and measures may reflect this origin.
Useful conversion factors:
- Area: 1 in² (square inch) = 645 mm²
- Mass: 1 oz. (ounce) = 28.35 g; 1 lb (pound weight) = 0.454 kg
- Length: 1 in. (inch) = 25.4 mm; 1 ft (foot) = 304.8 mm; 1 yard = 0.914 m; 1 mile = 1.609 km
- Pressure: 1 psi (lb/in²) = 68.95 mb
- Volume: 1 UK pint = 568.3 ml; 1 UK gallon = 4.546 litres; 1 US gallon = 3.785 litres
While most of the information is correct for all countries, certain information is specific to the North American market and may not be applicable to European users. Differences include U.S. standard external power supply details (e.g., AC transformer input voltage). Power supply adapters ordered will be suitable for the customer's country.
References to radio transmitters, digital cell phones, and aerials may also not be applicable according to locality.
Some brackets, shields, and enclosure options, including wiring, are not standard items in the European market. Alternatives may be offered and detailed in separate manuals.
Part numbers prefixed with a "#" symbol are special order parts for non-EU variants or special installations. Quote the full part number with the # when ordering.
Recycling information
At the end of this product's life, it should not be put in commercial or domestic refuse but sent for recycling. Batteries contained within or used during the product's life should be removed and sent to an appropriate recycling facility.
Campbell Scientific Ltd can advise on recycling the equipment and, in some cases, arrange collection and correct disposal, although charges may apply.
For further advice or support, contact Campbell Scientific Ltd or your local agent.
Introduction
The IR100/IR120 is an infrared temperature sensor offering a non-contact means of measuring surface temperature by sensing infrared radiation. It can be used for measuring leaf, canopy, and average surface temperature. Non-contact measurement is simpler to install, does not influence the target temperature, and provides a spatial average temperature.
Two sensor variants exist: the IR100 has an ultra-narrow field of view, while the IR120 has a narrow field of view (see specifications). This manual uses "IR100" to refer to both versions.
Specifications
General Specifications
| Parameter | Value |
|---|---|
| Field of View (half angle) | IR100: 4-5°; IR120: 20° |
| Dimensions | 92 mm long by 28 mm diameter |
| Mounting holes | 2 x 6 mm thread, 5 mm deep (min) |
| Response Time | <1 second to changes in target temperature |
| Target Output Signal | IR100: 5 mV per °C; IR120: 20 mV per °C (difference from sensor body) |
| Signal Offset | Removed by calibration (supplied) |
| Typical Noise Level (measured by CS datalogger) | IR100: 0.2°C RMS; IR120: 0.05°C RMS |
| Calibrated Range | -25°C below body temperature to +25°C above body temperature |
| Operating Range | -25°C to +60°C |
| Accuracy over Calibrated Range | ±0.2°C (against a blackbody source over a 50°C temperature span under laboratory conditions) |
| Current Consumption | 0.4 mA (excitation applied), 0 mA quiescent |
| Sensor output impedance | 320 Ohms |
| Thermopile Excitation Voltage | +2 to +3.5V |
| Thermistor Excitation Voltage | -2.5V |
Wiring
The IR100 is compatible with all Campbell Scientific dataloggers (except CR200) and most other dataloggers supporting negative voltage excitations. Wiring colors and connections are shown in Table 1.
Table 1. IR100 Datalogger Wiring Details
| Colour | Description | Wiring (SE) | Wiring (Diff) |
|---|---|---|---|
| Brown | Thermistor | SE Channel | SE Channel |
| Green | IR Temperature | SE Channel | Diff (x) High |
| White | Ground / IR Temperature | AG ⟁ | Diff (x) Low |
| Red | Excitation | EX | EX |
| Black | Ground | AG ⟁ | AG ⟁ |
| Clear | Shield | ⟁ | ⟁ |
The IR100 can be wired either single-ended (SE) or differentially (Diff) as detailed in Table 1.
Spectral response
Wavelength Range:
- IR100: effective bandwidth 7-14 µm (some sensitivity from 2-6 µm)
- IR120: 8 to 14 µm
Graphs illustrating the relative spectral response for IR100 and IR120 are available in the original document. The IR100 graph shows a peak response around 9-10 µm with some sensitivity extending to lower wavelengths. The IR120 graph shows a narrower bandpass, peaking around 10-12 µm and dropping off sharply outside this range.
A schematic diagram shows the internal components: a Thermistor (77020R, 30K @25°C) connected via the brown wire, an Amplifier, and a Thermopile detector. The wiring includes connections for Excitation (Red), Thermistor (Brown), Ground (White, Black), IR Temp (Green), and Shield (Clear).
Installation
The IR100 sensor should not be allowed to fill with water and should not be pointed skywards.
The sensor can be secured using one or two 6 mm screws to a flat surface, such as a metal mounting bracket (screws not provided). Older units had a ¼-20 UNC thread.
For optimal precision, the sensor body should be shielded from rapid temperature changes, direct exposure to wind, rain, and sun, and handling. Optional housings are available to protect the sensor and dampen temperature fluctuations, improving measurement accuracy.
The IR-SS Solar Shield is recommended for most outdoor installations. It protects the sensor from direct solar radiation and weather, preventing rapid body temperature changes that can cause transient measurement errors. The sensor mounts to suitable structures using a 6 mm threaded hole in the shield, for example, on the Part 009905 IR1x0 mounting arm designed for Campbell Scientific tripods and towers. Figure 1 shows an IR120 mounted inside the IR-SS shield on a 009905 arm.
Figure 1: A picture showing the IR-SS Solar Shield with an IR120 sensor fitted.
To install the sensor inside the IR-SS shield, use the provided nylon mounting pillars and 6 mm screws. Figure 2 illustrates the sensor positioned within the shield, with mounting holes facing downwards, the typical field orientation.
Figure 2: A cross-sectional diagram of the sensor fitted inside the IR-SS shield, showing the sensor body, mounting pillars (A, B), external screw heads, and cable connection.
With the sensor installed, the shield can be mounted on an arm or rigid structure. Position the shield to avoid direct sunlight into the sensor. Ensure the top end is not blocked to allow natural ventilation. Figure 3 shows the shield mounted on an IR1X0 mounting arm, secured with cable ties.
Figure 3: The IR-SS shield fitted onto an IR1X0 mounting arm, illustrating cable ties and the mounting bolt arrangement.
Optional band-clamp pole mounts are available for mounting the IR-SS on lamp posts and similar structures. Figure 4 shows an IR-SS fitted to a pole using a band clamp.
Figure 4: An IR-SS fitted to a pole with an optional band clamp fitting.
When installing with a band-clamp bracket, attach the shield to the bracket first. Mount the bracket on the pole, then attach the shield using the bolt, spring washer, and lock nut. Figure 5 details this arrangement.
Figure 5: The arrangement of the nut and washers on the band clamp fitting, showing the band-clamp bracket, spring washer, plain washer, and lock nut securing the shield tube.
After mounting, secure the cable to the pole with ties to prevent wind-induced flexing.
Consideration must be given to the field of view, distance to the target, and sensor angle relative to the target surface for accurate measurements. The field of view radius can be calculated using the formula: radius = tan(n) * target distance, where 'n' is the half angle of view.
Minimize the distance to the target to reduce errors from mist, water vapor, or dust. Point the sensor directly at the surface (90 degrees relative to the surface) rather than at acute angles, as surfaces can have increased reflectivity at low angles, potentially biasing readings towards reflections.
Principles of Measurement
Thermopile Detector
The IR100 sensor uses a thermopile detector consisting of series-connected thermocouples. One set of junctions is exposed to source radiation, while the other is shielded. A polished metal cone concentrates radiation onto the exposed junctions, which are coated with lamp-black for efficient absorption. The thermopile outputs a voltage proportional to the thermal energy balance between itself and the target surface.
A separate thermistor, embedded in the sensor body behind the thermopile, measures the reference body temperature. Both measurements are combined and processed by the logger to determine the surface temperature.
Thermistor
The thermistor's resistance varies with temperature according to the Steinhart-Hart equation:
1/T = A + B(ln(R)) + C(ln(R))³
Where T is temperature, R is resistance, and A, B, and C are calibrated constants specific to each thermistor. The sensor's calibration coefficients must be used in the program.
The Stefan Boltzmann Law
This law relates the temperature of a surface to the thermal energy it radiates. It states that the total energy radiated per unit time per unit surface area of a blackbody is proportional to the fourth power of its absolute temperature (in Kelvin):
E = σT⁴
Where σ is the Stefan's constant (5.67E-8 W m⁻² K⁻⁴).
The rate of radiation received from surrounding objects at temperature T is σT⁴, and the rate emitted by the blackbody at temperature T₀ is σT₀⁴. The net rate of energy loss is Enet:
Enet = σ(T⁴ – T₀⁴)
This leads to the formula for temperature:
T⁴ = Enet / σ + T₀⁴
Enet is determined from the amplified thermocouple voltage using a polynomial equation derived during calibration. The thermopile sensor's sensitivity decreases by 0.04% per °C; this is compensated for by increasing the multiplication factor by 0.04% for every degree Celsius above the calibration temperature using the formula:
Temperature_Compensated_x = x * 1.0004 ^ (IRcan_Temp - 25)
Correction for Non-Blackbody Surfaces
The IR100 is calibrated against a blackbody (emissivity ε = 1). Real surfaces reflect some radiation, which must be accounted for. The formula for surface temperature considering emissivity and reflected radiation is:
T⁴_surface = (T⁴_measured - (1 - ε)T⁴_reflected) / ε
Where ε is the surface emissivity (0 to 1) and T_reflected is the temperature of the surrounding surfaces contributing to the reflection.
It is often assumed that reflected radiation comes from surfaces at the sensor body temperature, but for outdoor applications, air temperature might be more appropriate. Algorithms in Campbell Scientific's road temperature monitoring equipment account for reflected radiation from the sky, buildings, trees, and environmental films.
Getting the best measurements
Accurate infrared temperature measurements require understanding the principles and careful sensor use:
- Emissivity: Measurement accuracy depends on knowing the surface emissivity. The further emissivity is from 1, the more critical compensation is.
- Target Angle: Point the sensor directly at the target (90°). Acute angles increase reflection errors, especially from sunlight.
- Distance: Install the sensor relatively close (within a few meters) to the surface. Mist and high humidity can affect readings by influencing the air temperature between the sensor and target. Avoid installing too close, which could interfere with IR exchange.
- Sensor Body Insulation: Shield the sensor body from rapid temperature changes. Small temperature gradients around the aperture can cause transient errors. Use a shield or insulation (e.g., foam pipe insulation) or an optional housing with an IR transmissive window.
- Aperture Check: Ensure the sensing aperture is not blocked (e.g., by spiders) and that any enclosure's IR transmissive film is clean and dry.
Program Examples & Explanation of Terms
IR100 Blackbody Infrared Temperature Measurement
Thermistor Measurement - Sensor Body Temperature
The following CR1000 example code obtains the sensor body temperature from the IR100's thermistor. A 20 ms delay is used for settling time on long cable runs.
BRHalf(IRSensor_can,1,mV2500,3,Vx1,1,-2500,false,20000,_50Hz,1,0)
IRSensor_resis=77020*(IRSensor_can/(1-IRSensor_can))
IRSensorcan_temp=1/(IRSensor_a + IRSensor_b*LN(IRSensor_resis) + IRSensor_c *(LN(IRSensor_resis))^3) - 273.15
A half-bridge measurement calculates resistance from the voltage ratio. This resistance is used in the Steinhart-Hart equation with calibration constants (IRSensor_a, IRSensor_b, IRSensor_c) to find the body temperature in Kelvin. A negative excitation voltage is used because the same wire powers the Thermopile amplifier with a positive voltage.
Thermopile Detector - Infrared Radiation Measurement
This CR1000 example code obtains a raw infrared radiation measurement. The IR100 has an internal amplifier requiring a positive 2500 mV excitation and a minimum 75 mS settling time.
Measurements can be made differentially (more accurate, especially for long cables, requires a differential channel) or single-ended (used when datalogger inputs are limited and cables are short, <10 m).
Single-ended measurement example:
'Single ended measurement - note the positive 2500mV 'excitation which is turned on first to force a 75mS delay
ExciteV(Vx1,2500,0)
Delay(0,75,mSec)
BrHalf(IRSensor_Volt,1,mV250,1,Vx1,1,2500,False,0,_50Hz,2500,0)
Differential measurement example:
'Differential measurement - note the positive 2500mV 'excitation which is turned on first to force a 75mS delay
ExciteV(Vx1,2500,0)
Delay(0,75,mSec)
BrFull(IRSensor_Volt,1,mV250,1,Vx1,1,2500,False,False,0,_50Hz,2.5,0)
Following these, temperature compensation and calibration factors are applied:
'Apply temperature compensation for the IR Sensor
IRSensor_Volt_TC = IRSensor_Volt * 1.0004 ^(IRSensorCan_Temp - 25)
'Apply calibration factors
IRSensor_E=IRSensor_x*IRSensor_volt^2+IRSensor_y*IRSensor_volt+IRSenso r_z
IRSensor_T4=(IRSensor_E/5.67E-8)+(IRSensorcan_temp+273.15)^4
IRSensor_T=IRSensor_T4^0.25-273.15
Note: Range codes may need amendment for CR3000 dataloggers.
IRSensor_E represents the measured thermal radiation. IRSensor_T4 and IRSensor_T are intermediate calculations for temperature in Kelvin.
Correcting for an enclosure window
When the sensor is installed inside an enclosure with a protective window (e.g., a thin plastic film with high IR transmission), additional code is required for correction. This is not needed for sensors in an IR-SS shield.
'Film IR transmission - CSL window - measured value
Const Film = 0.79
'The correction equation
IRTFilm_T4 = ((IRSensor_T4 - ((Airtemp + 273.15)^4 * (1 - Film))) / Film)
This correction uses air temperature (Airtemp) as a measure of the window temperature, assuming the window is shaded. The result IRTFilm_T4 is the corrected target temperature in Kelvin to the power of four.
Non-Blackbody Infrared Temperature Measurement
To obtain an infrared temperature measurement corrected for target surface emissivity (e.g., 0.94), assuming adjacent surfaces are at sensor temperature:
Emissivity = 0.94
Temp=((IRSensor_T4-((IRSensorcan_temp+273.15)^4*(1-Emissivity)))/Emissivity)^0.25-273.15
For measuring surface leaf temperature under a tree canopy, air temperature may be more suitable for the adjacent temperature than the sensor body temperature.
CRBasic CR1000 Program Examples
CRBasic example with Emissivity correction
This CR1000 program example demonstrates emissivity correction. It includes calibration data, emissivity setting, variable declarations, and the main program scan for measuring body temperature and infrared temperature, applying compensation and calibration factors.
CRBasic example with Emissivity and Window film correction
This CR1000 program example includes corrections for both emissivity and a transmissive window film, suitable for sensors in protective housings.
Edlog CR10X Program Example
This example provides Edlog code for a CR10X datalogger, demonstrating measurement of body temperature and infrared temperature. It includes calibration data, excitation, delay, resistance calculation, Steinhart-Hart equation, and temperature compensation steps.
Maintenance
The sensor contains no serviceable parts. For outdoor installations, check and clean the sensor to remove dirt or insects, especially within the tube at the free end. Use an air duster. If necessary, use a cotton bud dipped in electronics-grade alcohol to clean the detector window. Avoid scratching the silvered window.
Appendix A. Correction for Non-Blackbody used in Campbell Scientific's Road Temperature Monitoring Equipment
This appendix explains the correction method used in IRIS and other road surface monitoring equipment for understanding and applying similar techniques.
The radiation balance model for roads involves observed radiation (RadObserved) as a sum of components: radiation from a protective film (RadFilm), the road itself (RadRoad), the sky (RadSky), and surrounding buildings/trees (RadBuildings&trees).
The formula relating these is:
RadObserved = A(RadFilm) + B(RadRoad) + C(RadSky) + D(RadBuildings&trees)
Using the Stefan-Boltzmann Law (E = σT⁴), this can be rearranged to solve for road temperature:
TRoad⁴ = ((TObserved⁴) - A(TFilm⁴) - C(TSky⁴) - D(TBuildings&trees⁴))/B
Where:
- A = (1-Transmissivity)
- B = Transmissivity x Emissivity
- C = Transmissivity x (1-Emissivity) x SVF (Sky View Factor)
- D = Transmissivity x (1-Emissivity) x (1-SVF)
TFilm⁴, TBuildings&trees⁴, and TAir⁴ are all assumed to be at air temperature.
Appendix B. IR100 Thermistor Resistance
The following table shows the resistance (in Ohms) of the IR100 thermistor at various temperatures (in °C). Tolerance on these figures is ±5%. Individual calibration for each sensor is included on the calibration certificate.
| Degree C | Ohms |
|---|---|
| -25 | 363,300.0 |
| -20 | 273,420.0 |
| -15 | 207,600.0 |
| -10 | 158,910.0 |
| -5 | 122,580.0 |
| 0 | 95,355.0 |
| 5 | 74,655.0 |
| 10 | 58,857.0 |
| 15 | 46,716.0 |
| 20 | 37,320.0 |
| 25 | 30,000.0 |
| 30 | 24,261.0 |
| 35 | 19,734.0 |
| 40 | 16,140.0 |
| 45 | 13,272.0 |
| 50 | 10,971.0 |
| 55 | 9,114.0 |
| 60 | 7,605.0 |
| 65 | 6,378.0 |
| 70 | 5,372.4 |
| 75 | 4,544.4 |
| 80 | 3,860.4 |
| 85 | 3,292.2 |
| 90 | 2,818.8 |
| 95 | 2,422.2 |
| 100 | 2,089.2 |
| 105 | 1,808.1 |
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