RTD Testing Methods in Calibration Laboratory

Here we discuss the brief overview of different In-House testing methods carried out for RTD assemblies in the Calibration Laboratory.

RTD Testing Methods

The below list shows the different testing methods.

1. Calibration

RTD calibration can be done as per IEC 751 / DIN 43760 Class A & B.

Normally test is conducted for two points (i.e. 0⁰ C & 100⁰ C), 3 point calibration or more can be followed.

2. Insulation Resistance Test at ambient (room temp.) at 500 VDC

It should be more than 100 M ohms.

3. Insulation Resistance Test at 320⁰ C at 100 V DC

IR should be more than 2 M ohms. More than 20 M ohms also can be offered.

4. N2 leakage test

For the RTD sensor, after cap welding, the N2 leakage test should be carried out no leakage should be observed at 40 kg/cm².

5. Response time test

Response time test as per IEC 751 – (63.2% step change from ambient to 800C).

For RTD without transmitter – 6 to 9 sec up to 6 mm OD of sheath.

For RTD with thermowell – the response time will be 35 to 45 sec.

6. Special test

Autoclave test – RTD kept in steam @ 1250C & at 1.2 kg/cm2 for about 1 hour.

IR should be more than 5 M Ohms.

7. Continuity Test

By using continuity tester/multimeter – This test is used to confirm the element is connected properly to the RTD transducer cable.

8. Sheath Integrity Test

Water Immersion test – To check the sheath integrity of thermocouple / MI RTD cable.

9. Response time test with RTD connected to the pipe

Response time test for RTD with RTD connected to pipe on its outside surface to which water is flowing @ 20 ltrs. per second & @ 800C. The acceptance norm is less than 20 seconds.

10. Self-heating error test

It is in accordance with IEC 751

source: Prisma Instruments

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• Different Standards for RTD
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• Interview Questions on RTD