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Part Identification

by DailyDose
Tags: identification
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DailyDose
#1
Feb29-12, 04:35 PM
P: 25
Hey guys, I have no idea what in the world this part is. I Ohmed it out and it is about 60 ohms. I measured capacitance and it is around 50 nF. My first thought when I saw it was that it was a capacitor. But 50 nF... I talked to our technician and he mentioned a PolySwitch. I am a little skeptical of his answer. Any help would be greatly appreciated. The pictures are attached.
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MATLABdude
#2
Feb29-12, 07:48 PM
Sci Advisor
P: 1,724
It could very well be a self-resetting fuse (a.k.a. a PolySwitch):
http://en.wikipedia.org/wiki/Resettable_fuse

If you heat it up with a blow-dryer or heat gun, and see the resistance go up dramatically from the nominal 60 ohms, you'll probably owe your technician a beer or few. Clarostat used to start their component naming with CTI, but Googling for the part number turned up nothing.
DailyDose
#3
Mar2-12, 02:12 PM
P: 25
I did what you suggested and I am not sure what exactly I saw. I saw the resistance increase dramatically into the realm of megaohms but not never saw this resistance decrease. After giving it some time to cool down and then resetting my mulimeter, it still measure in the megaohms. But when I began to heat it up, the resistance decreased down into the kilo ohms. Did I potentially blow it up? Are these results expected from a self resetting fuse? Is there circuit test I can construct that would allow me to test and know for sure?

MATLABdude
#4
Mar2-12, 04:09 PM
Sci Advisor
P: 1,724
Part Identification

You probably overdid it. The self-resetting fuse is supposed to trip from the current going through it (which shouldn't be a great deal of heat). If it's still in the kOhm range at room temperature, it's probably pooched.
Mike_In_Plano
#5
Mar4-12, 05:56 PM
P: 560
How did you measure the capacitance with a DC resistance of 60 ohms in parallel? A high frequency RLC meter?

Anyway, the square shape is most commonly associated with self-resetting fuses. Otherwise, it might be an inrush limiter, which starts out with a few tens of ohms and drops to a few ohms when hot.


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