Making Sense of Sensors Part 4- Type E

Thermocouple Type E: Type E (Chromel®/Constantan) thermocouple is composed of a positive leg of Chromel® (nickel/10% chromium) and a negative leg of Constantan (nickel/45% copper).

The temperature range for this thermocouple is -200 to 900°C (-330 to 1600°F). The type E thermocouple manufactured by Pyrosales has the highest millivolt (EMF) output of all established thermocouple types.

Type E sensors can be used in sub-zero, oxidizing, or inert applications and is not subject to corrosion at cryogenic temperatures. A benefit below 800°C is the low drift rate. For example, 1000hrs at 760°C produces less than 1°C. In the minus °C range down to -250°C, type E is an excellent choice due to its low thermal conductivity and its output of approximately 8 microvolts per °C. These sensors are ideal for cryogenic, pharmaceutical, and chemical applications where critical measurements are required in small increments.

Considerations

Pyrosales recommend Type E should not be used in sulfurous, vacuum, or low oxygen atmospheres. It has similar calibration drift to that of type K, so the same precautions are recommended. They are not recommended for use in atmospheres that promote ‘green rot’ corrosion of the positive leg. Green rot corrosion can cause large negative errors in calibration. The drift size will depend on the temperature.

Although there is a benefit of low drift below 800°C, it should be noted that above 800°C, the negative leg oxidizes more rapidly than the positive, thus reducing both life and accuracy.

For assistance in choosing the proper sensor for your process, please contact us at Pyrosales and our Temperature and Process Engineers will be happy to assist you!

Continue reading… Part 5