Tool/software:
Hello,
tl;Dr:
- Is R68 a precise resistor?
- Do resistors like R68 have a negative or positive temp coefficient in general?
I am currently investigating the Evaluation-Board and using your pt-100 highside 4 wire setup for measuring. I am fairly new to hardware development and have some questions about the R_REF of the EVAL board.
In your basic guide for RTD Measurement, you state a more precise R_REF leads to a better measurement, because the error of drift gets minimized. (Assuming the system gets calibrated to a known temperature(removing the initial accuracy error)).
Is R68 considered precise?
I looked into the specs of the R68:
From the datasheet I got
- 1 k Ohm
- 0.1% Tol
- 25 ppm/C
Are these specs correct?
Is 25 ppm/C considered low drift? There are resistors available with lower ppm.
The first measurements show a drift. The measurement environment is not regulated, so I am not sure if this is due to temperature changes. But I observed a neg. voltage-drift when the room heated up (In the morning when I start the heater in the office) and a positive voltage drift when the room gets colder.
When the resistor has a pos. coefficient this would mean V_REF rises and the measured Voltage would drop(Lower codes). This would correlate to my observation.
Is this correct?
Measurement Settings:
- Global chop enabled
- SPS 5
- sinc 3 filter enabled
- 100 Ohm resistor to simulate 0 C(maybe also a drift source)
Thank you for your time 
Regards
Johanes
