How to Adjust the Emissivity Setting of an Infrared Temperature Sensor

Most infrared temperature sensors have an adjustable emissivity setting. Here’s how to use this powerful feature to achieve accurate measurements from a variety of surfaces.

Emissivity is a measure of how effectively a surface emits infrared radiation. For an accurate temperature reading, the emissivity setting of the sensor must match the emissivity of the surface being measured.

For non-reflective non-metals and painted surfaces, the emissivity is usually about 0.95. This is the default emissivity setting of all Calex sensors. However some materials have a different emissivity, and to fine-tune the accuracy of the measurement, the sensor’s emissivity setting should be adjusted to match.

The emissivity setting is adjusted in different ways on different types of sensor:

Rotary switches

The emissivity setting on PyroMini CB models is adjustable via 2 rotary switches in the electronics module. For example, for an emissivity setting of 0.95, set the switches to “9” and “5”.

Touch screen interface

On PyroMini, PyroMini 2.2 and FibreMini BRT and CRT models the emissivity setting can be adjusted via the built-in touch screen interface. Unlock the interface by entering the password, then go to Settings – Emissivity & Compensation to find the setting.

Modbus versions of the PyroMini, as well as the PyroBus, PyroMiniBus and FibreMini sensors, are compatible with the PM180 multi-channel touch screen interface. This can be used to change the emissivity setting of each individual connected sensor.

The PyroCube is configurable via the PM030 touch screen module.

NFC (smartphone or tablet)

Using the free Android app, the emissivity setting of the PyroNFC can be adjusted using an NFC phone or tablet. In the PyroNFC app, go to “Emissivity Setting”. Enter the value, tap “Save”, then on the main screen tap “Write to Sensor”. When you hold the device to the PyroNFC, the emissivity setting will be updated. A message appears to confirm the Allow 5 seconds for the new setting to take effect.

Note: Apple has not yet allowed developers to access NFC on the iPhone, so the app is currently available for Android only.

Continuous adjustment via 4-20 mA input

The emissivity setting of the PyroEpsilon is adjustable via any 4-20 mA source providing a continuous signal, such as a PLC output, or the optional PyroTune emissivity adjuster. The 4-20 mA signal corresponds linearly to emissivity setting range of 0.2 to 1.0.

This way, the emissivity can be adjusted continuously during the process. This is ideal for applications such as pipe coating where the bare metal pipe has a low emissivity before coating, and the coated pipe has a high emissivity.

Digital communications (Modbus)

Another way to adjust the emissivity setting “on-the-fly” is by using Modbus. This is possible on the Modbus versions of the PyroMiniPyroMini 2.2 and FibreMini as well as the PyroMiniBus, PyroBus, PyroMiniUSB and PyroCube. Write the emissivity value to the Modbus register for “Emissivity Setting”. Please check the instruction manual of your sensor to find the Modbus register of the emissivity setting.

Software

By connecting the sensor to a Windows PC via USB, the following sensors can be configured using software:

PyroUSB and PyroUSB 2.2: via CalexSoft

PyroMiniUSB: via CalexConfig or your own Modbus software

ExTemp: via CalexConfig (connected to the PC with the LCT loop configuration tool on the safe side of the Intrinsically Safe isolator).

More Information

Check out our Guide to Emissivity for more information.

By Anthony Smith