Originally posted by Guruji
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you are right! Digital MMs do not measure correctly in this application.
One way to measure correctly is to conduct two measurements.
1. Glue a PTC or NTS on a load resistor (not wire wound because of inductance) Choose value of resistor according to your optimal load.
2. Connect this resistor to your setup as load. Leave free air around the resistor.
3. Measure the resistance of your PTC/NTC until it reads stable.
4. Connect the load resistor to a variable power supply. Do not move the resistor.
5. Adjust the voltage so that you get the same stable reading like before.
6. Measure Voltage and amperage
7. Multiply measured voltage times amperage
8. Here you are: measured TRUE power.
The charm of this method is that you can take any NTC/PTC and there is no need for any calibration. The quality of a normal DMM is suffitient.
rgds John
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