Fixed Infrared Temperature Sensor with Adjustable Emissivity


  • Temperature ranges from -20°C to 500°C
  • 2-wire 4-20 mA output for measured temperature
  • Emissivity adjustment via separate 4-20 mA input
  • 4-20 mA input signal may be supplied by the optional PyroTune emissivity adjuster (pictured), DRR245 indicating controller, or any other source such as a PLC output
  • Stainless steel housing, sealed to IP65
  • Choice of optics to suit all target sizes
  • Not designed or approved for fever detection
Field of View -20°C to 100°C 0°C to 250°C 0°C to 500°C
2:1 PE21LT PE21MT *
15:1 PE151LT PE151MT PE151HT
30:1 PE301LT PE301MT PE301HT

*For sensors with 2:1 optics and 0°C to 500°C temperature range, contact Calex.

General Specifications

4-20 mA (two-wire, on power loop)
± 1% of reading or ± 1°C whichever is greater
± 0.5% of reading or ± 0.5°C whichever is greater
Emissivity Setting
Adjustable from 0.2 to 1.0 via 4-20 mA input
Response Time, t90
240 ms (90% response)
Spectral Range
8 to 14 μm
Supply Voltage
24 V DC (28 V DC max.)
Min. Sensor Voltage
6 V DC
Max. Loop Impedance
900 Ω (4-20 mA output)
Input Impedance
50 Ω

PyroTune Emissivity Adjuster Specifications

4-20 mA
Supply Voltage
24 V DC (13 V to 28 V DC)
Display Format
3.5 digit LCD
Display Units
Emissivity (0.2 to 1.0) or current (4 to 20 mA)
Push-buttons (raise/lower/set)
Polycarbonate with gasket, transparent lid (PC) and quick release screws
65(h) x 50(w) x 35(d) mm
72 g
Environmental Rating
Ambient Temperature Range
0°C to 70°C
Relative Humidity
95% max. non-condensing

Field of View Diagrams

Please note: The given measured spot size contains 90% of the energy detected by the sensor. We normally recommend the target is at least twice as large as the given measured spot for maximum accuracy. Sensors may be used at longer distances than the above diagrams show. There is no maximum measurement distance in clean air; this is because the PyroEpsilon detects only the wavelengths of infrared radiation that are not absorbed by the atmosphere. 2:1 optics are not available on sensors with temperature range 0°C to 500°C as standard. Please contact Calex for more information.

Mechanical Specifications

Stainless Steel
Diameter 18 mm x length 103 mm
Thread Mounting
M16 x 1 mm pitch
Cable Length
1 m (longer lengths available to order)
Weight with Cable
95 g

Environmental Specifications

Environmental Rating
Ambient Temperature Range
0°C to 70°C
Relative Humidity
95% max. non-condensing

Electromagnetic Compatibility Standards

Conforms with EN61326-1, EN61326-2-3 (Electrical Equipment for Measurement, Control and Laboratory Use – EMC Requirements – Industrial)

The emissivity setting of the PyroEpsilon infrared temperature sensor is adjustable via an analogue input, so it can be controlled automatically during the process, for example by a PLC, or manually, by using the controls on the optional PPT245 indicating controller or the optional PyroTune emissivity adjuster. If the emissivity of the target changes during the process, then the PyroEpsilon is ideal.

The PyroEpsilon is also a good choice if a simple pyrometer with a 4-20 mA output is required, but you are not sure if the emissivity of the target surface is high enough for a fixed-emissivity sensor to be suitable. When no 4-20 mA input signal is present, the emissivity setting will default to 0.95. Emissivity adjustment may then be added later on if required.

The PyroEpsilon may be used in many applications, including the following:

Typical Applications

Measurement of the temperature of food production equipment including bakery trays and plastic moulds. Surface temperature of PTFE coated rollers.
Paper and Packaging
Glossy or shiny paper temperature
Thermoforming temperatures, temperature of plastic bottle parison tubes before inflation in blow moulding
Power industry
Measuring the temperature of painted surfaces in switchgear cabinets, generator housings
Pipe coating
Measurement of pipe temperature during coating where the emissivity of the surface increases during the process
Condition monitoring
e.g. painted bearing housings, driveshafts, rollers and gearboxes. Turbine housing temperature measurement. Monitoring the outer surface temperature of boilers and pipes

The sensor is supplied with a cable length of 1 m as standard. Longer lengths are available to order; please contact Calex for more information.

Connecting the PyroEpsilon:

1. Connect only the power wires PWR+ and PWR- to a 24 V DC powered 4-20 mA measurement loop. Connect the emissivity input wires IP+ and IP- to each other, and do not connect them to the power supply.

2. Obtain a temperature reading without emissivity adjustment.

3. Connect IP+ and IP- to a 4-20 mA current source if emissivity adjustment is required.

Electrical Installation

Dimensions (mm)

DRR245 Indicating Controller

The DRR245 indicating controller provides a 4-20 mA signal for adjustment of the PyroEpsilon’s emissivity setting, as well as a display of the measured temperature and configurable relay outputs for alarm or control.

Product details >


PyroTune Emissivity Adjuster

Provides a 4-20 mA signal for emissivity adjustment. The push-buttons allow adjustment of the emissivity setting, and the built-in display shows either the emissivity setting or the milliamp signal being supplied to the sensor.

Air Purge Collar

The air purge collar is used to keep dust, fumes, moisture and other contaminants away from the lens. Air flows into the fitting on the side and out of the aperture at the front.


Fixed Mounting Bracket

The L-shaped fixed mounting bracket offers a rigid support for the sensor and allows fine rotational adjustment about one axis.

Adjustable Mounting Bracket

The adjustable mounting bracket consists of a fixed mounting bracket plus another L-shaped bracket. When assembled as shown, the adjustable mounting bracket offers a rigid support for the sensor and allows fine two-axis adjustment.

Air/Water Cooled Housing

The air/water cooled housing allows the sensor to withstand ambient temperatures above the normal 70°C limit. Depending on the degree of cooling required, air or water may be used as the cooling fluid. To prevent condensation forming on the lens, an air purge collar is included with this item. The air/water cooled housing must be ordered with the sensor and cannot be fitted by the user.

Laser Sighting Tool

The Laser Sighting Tool screws onto the front of the sensor during installation and shows precisely where the sensor is aiming. Once the sensor has been aimed at the centre of the target and locked in position, the Laser Sighting Tool can be removed. The laser is operated via a latching push button on the front of the tool.

Dual Laser Sighting Bracket

The Dual Laser Sighting Bracket is a sturdy mount for the sensor and provides continuous target sighting while measurements are being taken. Two parallel lasers indicate the centre of the measured spot and are controlled by a remote switch on the electronics module. View data sheet (PDF)

Protective Plastic Window

When fitted over the lens of the sensor, the protective plastic window in stainless steel holder provides mechanical protection and helps retain fragments of lens in case of damage. Adjust the sensor’s emissivity setting to compensate for the presence of the window for maximum accuracy. This accessory is ideal for the food and pharmaceutical industries.

Ordering Information