I have an old (1990ish) digital thermometer with finger sensor that I use for biofeedback. The sensor in the finger band broke. I think the component might be a thermister. It is just a tiny black square, about the size of a surface mount resistor. The solder pads have broken off.

When I use a resistance substantiation box in place of the finger sensor the thermometer reads 93.4' with 6.8K, 46.1' with 22K, 0' with 33K (temps in 'F)

Any best guess on what to replace it with (and maybe some links)

 

That’s a negative temperature coefficient thermistor. Search for NTC 10K 3950. Look for 1% rather than 5%

 

It might be possible to solder to the open ends of the broken off solder pads. You would need to attach some very fine extension leads , and emmbed the assembly in a small bit od epoxy to support the repaired portion. That would take some fine soldering skill, though. And a lot of patience.

 

Thermistors are categorized by the resistance at 25°C.
10k Ω @ 25°C is a common value.
Hence you can either find the resistance that gives 25°C or you can insert 10k Ω and see what it reads.

I have found about 87 SMD thermistors on the Digikey site.

Here is the first one at the top of the list.

https://www.digikey.com/en/products/detail/tdk/NTCG103JF103FT1/614628

 

Thanks everyone.