When I was wiring my Keithley 2000-SCAN card, I found a little component hidden inside the connector for channel 3. I hadn't spotted it before, just saw it during my work.
I initially thought it was a wire bridge used to measure the relay resistance. But it was a tiny component:
A little device on a ceramic chip.
I regret that I didn't take a photo first. Fortunately, I saw that it was visible on a photo I took for my first blog (and I hadn't deleted the original high resolution version yet):
I measured it, and it was around 100Ω. 108Ω actually. I thought that it could be a shunt for current measurement. But that's not very precise for a 100Ω resistor. When I touched it, I saw that the resistance increased fast. And that's when I realised it's a local temperature reference: Pt100 /RTD. The Pt100 is a common player in the measurement- and control (control theory) practice.
I found one on the e14 shop that looks very similar to the one embedded in my card: NB-PTCO-152 RTD SENSOR, THIN FILM PLATINUM, 100R. The photo on the Farnell page isn't the same, but the picture in TE's datasheet is very similar. The blackish look of the leads on my component seem to point that they are the silver version.
Mystery solved
