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I am a High School Junior doing a product breakdown for a school project, and I was wondering if one of you could help me identify a component or just tell me that it is a type of Chip On Board (which is what I suspect)? It is a digital thermometer (a really cheap one, about $10). The component that I need help identifying is the little black one that sticks out of the top of the circuit-board (next to the white wires and crystal oscillator).

PCB1

PCB2

Thanks in advance!

Oskar

EDIT: added the following to clarify that I know what the big black blob is and the location of the component: "(next to the white wires and crystal oscillator)"

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  • \$\begingroup\$ The one sealed under the black goo? Only the manufacturer can tell. \$\endgroup\$
    – Eugene Sh.
    Commented Jan 26, 2018 at 18:20
  • \$\begingroup\$ Yes and perhaps no, I mean the one with legs sticking out of the PCB (next to the crystal oscillator), I suspected that it might be some type of glob-on... Do you think that anyone could make a guess based on the PCB-markings? EDIT: Thanks for the answers! \$\endgroup\$
    – Oskar Stenberg
    Commented Jan 26, 2018 at 18:24

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The part with two pins and a black bead sticking out past the edge of the board looks to be a thermistor (temperature-sensitive resistor). You can disconnect it from the PCB and measure its nominal resistance at room temperature with a resistance meter. My guess is it'll probably be 10k (a very common value), but it could be just about anything. Then cover it with your fingers and see if the resistance goes up or down. If it goes up then it is a PTC (positive temperature coefficient) thermistor, and if it goes down it is an NTC (negative temperature coefficient) thermistor. I use a 10k NTC thermistor on a lot of products at work that looks nearly identical to this one (not that that says much) but it is a PR103J2 from US Sensor. If you're lucky maybe this is similar.

The black blob on the top side of the board is a COB and is probably an ASIC (application-specific integrated circuit) die covered up in goop. That will most likely be a custom part and will not be identifiable.

enter image description here

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  • \$\begingroup\$ Thanks! The thermistor was what I was looking for (my post was perhaps not as clear as I wanted it to be)... Thank you for the quick answer! Will mark as answer as soon as I can. \$\endgroup\$
    – Oskar Stenberg
    Commented Jan 26, 2018 at 18:29
  • \$\begingroup\$ I had a feeling you were referring to the part sticking out the edge but wasn't sure if I misunderstood the question. Good to know I understood it correctly though! \$\endgroup\$
    – DerStrom8
    Commented Jan 26, 2018 at 18:30
  • \$\begingroup\$ I feel like an idiot, I just read on the box and realized that it also measures inside temperature (and then I realize why that must be a thermistor, since there does not seem to be any other internal temperature probes). Thanks for the quick help! \$\endgroup\$
    – Oskar Stenberg
    Commented Jan 26, 2018 at 18:31
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    \$\begingroup\$ Absolutely... upvoted Q and A... And it's a good example question for some other posters to follow - quality pics and question. \$\endgroup\$
    – Solar Mike
    Commented Jan 26, 2018 at 21:09
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    \$\begingroup\$ @DerStrom8 Thanks! I have now gained enough reputation to upvote, so here I go :) By the way, that is a really helpful answer. The internet needs more people like you (and the other people in this comment section), on some forums I tried before I realized stackexchange was a thing I just got ridiculed and mocked... Thanks for the awesome help and keep up the good work! \$\endgroup\$
    – Oskar Stenberg
    Commented Jan 26, 2018 at 23:11

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