pt100 probes

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[email protected]
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Joined: Tue Sep 27, 2011 7:26 am
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pt100 probes

Post by [email protected] »

i just received 3 jld612, controllers and 3 pt100 probes, all 3 probes are open between red and blue, when 1st remove from package resistance between red and blue was about 110 ohms, room temp. all controllers display EEEE which they should with open input. is there anyway to remove sensor from probe to fix, i don't need the ssprobe, i'm measuring air temp, i was gentle with the probes, don't understand what could have happend
richiem
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Re: pt100 probes

Post by richiem »

It could be that your ohmmeter destroyed the platinum sensor by forcing too much current through it. The Pt100 sensors are not very rugged electrically and are designed to work with low currents applied to them. Some ohmmeters use higher voltages and currents on low ohms measurements and that can cause damage.

If you can, check the open circuit voltage between the test lead tips of your ohmmeter on the 200 ohm range with another DC voltmeter -- if you see more than 1 volt, don't use it for testing the Pt100 probes. You can safely test the probes for continuity, shorts, or opens by using a high resistance range of the ohmmeter, say the 20k, or better, the 200k range, depending on the number of digits of resolution available -- this will limit the current through the probe, even if the open circuit voltage at the leads is relatively high.

I personally think that warnings about testing the test equipment should be included with these probes....
Tech_Marco
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Re: pt100 probes

Post by Tech_Marco »

Thanks Rich for the info. I never though about that! You're right, some meter used higher voltage/current for low range resistance measurement and it could destroy some LED, that I known.

I was wondering how come so many PT100 got problem, but when I tested a few taking from my shelves with my DPM, I hardly find any doa. Plus, the manufacturer did say that they tested each before shipping. They were wondering as well.

Anyway, David, please send it back for exchange.

Marco
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