Sensor Selection

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 precalibrated range and security from accidental sensor adjustment after installation. 

Example For the following situation: 

1) K-type readout 

2) Target Material; black conveyer belt 

3) Target temperature; 300°F (1500°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, (270°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 (1500°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.