An associate is being encouraged to dump his old technology, but trusty resistance decade box used to check calibration of RTD inputs for a handheld electronic multipurpose calibrator by a big name test and measurement instrument vendor.

Multipurpose means it's supposed to do the industrial basics: current, DC volts, and resistance for RTDs.

Back in the early '90's I had a bad experience with a calibrator that was supposed to be a resistance source for calibrating 100 ohm DIN 385 RTD inputs. It would not work on 3 of the 4 different devices we had.

I'm not sure how a dynamic device substitutes 'resistance' into a live circuit with a constant current pump, but my ignorance shouldn't matter, it was marketed for RTD input calibration. (In keeping with modern technology, the details of what and how it was supposed to work were unpublished, apparently reserved for the manufacturer's elites, none of whom was available for comment.)

The manufacturer was located in western Europe and had only a sales office in the US, and was unable to resolve our dissatisfaction with the dysfunctional resistance source. We returned the device after our 30 day trial was up.

Since then, I've been skeptical of claims of 'dynamic' resistance source devices. A resistor or a series string of them might be passive, but they do the job. Maybe the one I used was an early poor design, then again, maybe they're all flakey.

Does anyone here have multiple positive experiences with non-decade box electronic resistance sources that they'd be willing to share?

 

See if you can borrow one and try it out.

--
Bob

 

Exactly. That was my thought when I read the thread title -- "You mean a resistor or decade box?"