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OWON XDM1041 the unknown multimeter...
davebb:
Good afternoon
The flukes 189 spec say 10A continuous and 20a for 30sec
The fluke is measuring well against my load and psu amp meter and all other meters ,
anyway the shunt wire has a lot of solder on it on the shunt/ component side so i wicked some off and moved it a bit and now i am getting a reading of 32.5ma high at 5A, and 65ma high at 10A, I could Play with it some more but i am happy to leave it there,
Thanks Dave
theHWcave:
Very interesting. I never thought a bit of solder could have that much of an effect, I mean assuming it did not "climb" up the shunt itself. So before the shunt resistance was lower than it should have been and the meter was under-reading. Now it seems pretty much spot on (within tolerances). Glad that its working now.
At the moment I am struggling with a similar problem for one of those cheap panel meters that measures DC volts & amps. The amp reading is way too high even when adjusting the trim-pot all the way down. I experimentally added a parallel shunt of 0.2Ohm and that got it nearly there. After your experience maybe I should add more solder to the shunt? I am very tempted to try that.
davebb:
Hi
Yes, after how much difference the solder getting wicked up the legs of the shunt so yes the solder did climb up the shunt legs,i should have taken a photo, there was a lot of solder on the legs ,
i may well try and get it a little bit closer, but it is working well,
try tinning your shunt,you wont need much solder on there, you can always use solder wick to clean it back off
In a way i wish i had sent the meter back before playing with it, because of the temperature problem ,
it does seem strange how this got past there cal and QA, as the current was way out of spec,
i got a owon ow18e h/held meter to use at work as it has bluetooth and that is ok for £45, i work on a car x-ray unit it was drive thru, now we have it on a conveyor system controlled by a plc with 4x 3ph motors each with 500nm of torque,
we run the xray gen at, 250kv at 3ma ,so with bluetooth i dont have to get to close when testing,
Thanks Dave
coromonadalix:
Be careful, i've seen in the past some obscure ways to calibrate a shunt with added solder on it. Not a the pcb / shunt junction but on the "wire itself" ??
Kleinstein:
Adjusting shunts by adding solder and removing matrial with a file was common in the old days of analog meters and early DMMs. Adding solder, especially in the center of the shunt can alter the TC as the solder resistance contributes and there is also some alloying (e.g. tin is incorporated into the base material).
Modern meters usually use numerical cal factors and thus calibration by a software constant.
I would be a bit careful in assuming that a used Fluke handheld DMM must be accurate. Usually the factory calibration is no that bad. There can be rare exceptions, like there can be damaged DMMs.
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