I'm trying to repair a broken baby monitor and found an interesting looking part. It looks like an thermocouple but I'm not sure. Do you have any ideas?
See board picture.
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\$\begingroup\$ Do you have the model number for this device? It appears to be a TC like you said, but if we can get a look at the diagram via the exact model number, it will give us a better idea of what it is. \$\endgroup\$– biggi_Apr 22, 2014 at 19:41
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3\$\begingroup\$ I don't. A thermocouple is quite unlikely in something like a baby monitor. If temperature sensing is needed at all, it is much more likely a thermistor is used in a high volume and cost-sensitive product like a baby monitor. \$\endgroup\$– Olin LathropApr 22, 2014 at 19:48
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\$\begingroup\$ It's a Padwico 938 baby monitor. Unfortunately I don't have schematic and board doesn't have connection point marks :( \$\endgroup\$– Farid83Apr 22, 2014 at 20:03
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\$\begingroup\$ The growing consensus is that it's a thermistor, you've reported it has a resistance -- don't keep us in suspense, does the the resistance vary when you heat or cool it? \$\endgroup\$– gwidemanApr 23, 2014 at 0:54
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1 Answer
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To me, this looks more like a thermistor than a thermocouple.
Can you measure the resistance across this part? If it's zero Ohms (short), then it's a thermocouple. If it's on the order of 10kΩ at room temperature, then it's a thermistor.
What materials are the wires made of? If they are both copper, then it's certainly not a thermocouple.
Can you describe what was this connected to inside of the unit? If it's connected directly to the microcontroller, then it's probably a thermistor. Thermocouples have weaker signal than thermistors, so they require more signal conditioning.
answered Apr 22, 2014 at 19:44
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\$\begingroup\$ Seems like it's indeed a thermistor. Resistance is 40K and both terminal wires are made of copper. It was broken off main unit and I'm trying to identify where exactly they're meant to be connected. \$\endgroup\$– Farid83Apr 22, 2014 at 19:51
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\$\begingroup\$ But did the baby monitor report temperature or not? Why should anybody put a thermistor in such a thing? \$\endgroup\$ Apr 22, 2014 at 20:10
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1\$\begingroup\$ Yes, it reports temperature. At least used to. \$\endgroup\$– Farid83Apr 22, 2014 at 20:13
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1\$\begingroup\$ @VladimirCravero Our baby monitor measures ambient temperature and reports it to the remote unit(s)... I never felt the need to look at it, though :) \$\endgroup\$– bitsmackApr 22, 2014 at 20:25
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1\$\begingroup\$ "Where it was connected" > There are two conspicuous solder blobs at the very edge of the board at top right of the board picture. Are they currently connected to anything? If not, they might be the connection points. \$\endgroup\$– gwidemanApr 23, 2014 at 0:56