Exergen Infrared Thermocouple Non-Contact Temperature Measurement

Selection Guide

The part number of an IRt/c sensor is made up of three parts:

Model Number - Thermocouple Type -Temperature Range,
for pre-calibrated sensors e.g. IRt/c.3X - J - 440F1220C

Model Number - Thermocouple Type -HiE or LoE,
for adjustable models e.g. IRt/c.20A - K - LoE

To select a model for an application, answer the following five points in order. You should then be in a position to select the optimum sensor.

1. Type of Controller / Transmitter / Input

Most sensors are available in J, K, E or T types. The thermocouple type should be the same as the readout/controller input type.

2. Target Material.

Virtually all non-metal surfaces are good emitters and work well with IRt/c sensors (Tech Note #31). If a target is to be viewed and it cannot be coated or an uncoated metal masked, a LoE model must be selected (Tech Note #21).

3. Target Temperature

Exergen offers 8 pre-calibrated temperature ranges for convenience (Tech Note #49). The sensors can be used outside their calibrated ranges, up to the temperature limit;with stated repeatability:

550°F limit: IRt/c.01 and IRt/c.03
1200°F limit: IRt/c, IRt/c.1X, IRt/c.3X, IRt/c.5 and IRt/c.10

4. Target Size and Distance Between Sensor and Target

The target should completely fill the field of view (Tech Note #55). As an example, the IRt/c.3X has a 3:1 field of view, this means that at a distance of 24" from the target the sensor will view a 8" diameter spot (spot size = distance ÷ 3). All of the IRt/c sensors have a minimum spot size (this minimum spot size varies with model type). It is not recommended that a sensor be used with a target smaller than the minimum spot size. Based on the minimum spot size:

For a target <0.3" (8mm), select a focused unit

For a target 0.3-0.8" (8-20mm), select IRt/c, IRt/c.01, IRt/c.03, IRt/c.1X or IRt/c.3X

For a target >0.8" (20mm), select any sensor.

5. Ambient Temperature and Environment

The IRt/c.01 and IRt/c.03 can be used in ambient temperatures up to 160°F (70°C). All of the other sensors can be used in ambient temperatures up to 212°F (100°C) without any external cooling.  Above 212°F the IRt/c can be used with the CJK-1 cooling jacket and the IRt/c.3X can be used with the CJK-2 cooling jacket (see accessories). The IRt/c.5, IRt/c.10 and all of the adjustable sensors have a built in air purge that can be used to cool to ambient temperatures up to 450°F (230°C).  If the environment where the sensor is placed is prone to be dusty or otherwise dirty, it is good practice to select a sensor with an air purge.  If linearization software can be employed in the readout device, HiE and LoE models can be supplied in a pre-calibrated form (see Tech  Note #96). This allows for the convenience of a pre-calibrated range and security from  accidental
sensor adjustment after installation.


For the following situation:
1) K-type readout
2) Target Material; black conveyer belt
3) Target temperature; 300°F (150 0 C)
4) Target size and distance; belt 24 (61 cm) wide, sensor 1.5 (3.8 cm) away.
5) Ambient temperature and environment; ambient 80°F, (27 0 C) oil vapors present

For this application the best sensor to select would be an IRt/c.3X-K-280°F/140°C. The sensor type must be a K-type to match the readout. The target material is highly emissive.  The temperature range is converted easily by this sensor and the 280°F/140°C calibration range from the temperature selection guide is the best one for 300°F (150 0 C). The IRt/c.3X has a 3:1 field of view, at 1.5" (3.8 cm) distance it will have a spot size of 0.5" (1.3 cm); this sensor has a built-in air purge which would be useful to keep the lens clean from oil vapor.

Also see the Accuracy Table and Selection Chart.

McGoff-Bethune, Inc.
5970 Unity Drive Suite A
Norcross, GA 30071
770-840-9811    800-303-4705     Fax: 770-840-7514
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