8508A RESISTANCE MEASUREMENT vs. PRT RESISTANCE

[wijogr]

I'm seeing a difference between using the 4-wire 200 Ohm LoI and 2 kOhm readings vs. the PRT resistance displayed on the right screen of the 8508A in PRT mode. I think I'm missing a setting but can't figure out what it is. The PRT measurement does not use FAST so I have that turned off in the resistance function. Ohms Guard is set for both functions. I=1 mA for all three. Low pass Filter is on. Both resistance ranges have been Zeroed. Any ideas?

[Mr M.]

Temperature uses 4-wire current reversal resistance measurement, this would be the equivalent of the TRUΩ setting.

[bAdbOb]

The current changes when you change ranges. I believe 1 mAdc is the usual current used for RTDs.

[NC-Cals]

The manual has you zero the 200Ω range in LOI (1 mA) and the 2kΩ range in 1 mA. This is outlined on page 3-27 of the user manual. You have to zero the ranges before you switch to PRT. There are also instructions on setting up for 3-wire PRT measurement.

[wijogr]

Thank you for all the suggestions. I was not using the TRU Ohms setting in resistance.  After running two tests it is working perfectly. Thanks again.