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OWON XDM1041 the unknown multimeter...

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theHWcave:

--- Quote from: Kleinstein on June 10, 2021, 05:11:10 am ---Pt100 is problematic with 2 wires. 3 wire mode is usually not supportedd by DMMs. Bendch DMMs usually support 4 wire mode - though it looks like the XDM1041 does not. With 2 wire connections it would be better to use Pt1000 instead of Pt100.

The accuracy of thermocouples is often nor very good, but the error is usually more like a percentage of difference to the room temperatur. At essentially the room temperature there is not much error from the TC itself. There can be some error from the connectors, from lokal temperature gradients. It is more the PT100 sensor that can have an offset-error.

--- End quote ---

Totally agree with that, although you can use 3-wire as I described in my previous post with REL to null the wire resistance. Unfortunately the XDM1041 ignores the REL value for Ohms when using the PT100.  With PT100 the error caused by wire resistance can be significant. My probe has 0.262 Ohm (2-way) wire resistance. Without REL, this adds to the resistance of the sensor. At 5 deg C, that causes an error of 13%, at 10 deg.C still 6.5%, 20 deg.C 3.3%. Only for >70 deg.C will the error be 1% or less.  So for high temperature measurements, the PT100 is usable in the XDM1041, for room temperature sadly not (unless you change the sensor wires to have very little resistance).

theHWcave:

--- Quote from: davebb on June 09, 2021, 10:30:19 pm ---Hi Have you tried a PT100 to see if that works ok, does the meter still use the same temp in the HY3131 for 10min cal
Thanks Dave

--- End quote ---
I tested this today and as expected, there is no 10min cal cycle in PT100 mode

davebb:
ok thanks
it would be good to know what this new firmware that misk has now got and if it still does this,
Thanks Dave

theHWcave:
Yeah, same here. After I saw Misk's post, I send an email to OWON asking about it....  but no response (so far). I'll post if I hear anything

I did an interesting test yesterday using a Peltier element cooling an old heat sink = chunk of aluminium. I had a PT100, the unknown K-type I normally use for the XDM1041 and a known (RS-components) K-type which I use for my BM869S all attached to the same area on that heat sink.  Long story short, it seems as if the XDM1041 was much closer tracking the PT100 when it used the RS-components K-type. That one, RS stock# 409-4920  costs nearly £8 (incl. VAT) and is still only rated as +- 1.5 degC, so I'd imagine the unknown one to be much worse. Side note. To use the RS K-type (or other more professional sensors) you need a K-type adapter. I use the Brymen BKB32 for around £5 from Telonic

davebb:
Good afternoon
Thanks for the info, i hope you do get a replay  from owon
i will get a PT100
Thanks Dave

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