Products > Test Equipment
OWON XDM1041 the unknown multimeter...
davebb:
Hi yes you are correct it has changed the temp by about 2 dg/c by turning the screen brightens to 0, and i have moved the meter in to free space only reading about 2.5dg/c high now,
Please let me know if you find anything more,
Thanks for your Help
Dave
Misk:
Sorry for my english. I buy OWON XDM1041 and I have a problem with it. Problem in this video https://www.youtube.com/watch?v=rcfSdUYxkVM. The measuring of megaoms resistors is bad and unstable. I think the HY3131 is bad. Can anyone measuring the 10MOm resistor on a analog board of XDM1041 near the HY3131 (conected to 5 pin from end). I measuring 8 MOm and the risistance change, when I repositing my body and other objects. When I touch the board it change to 6MOm. The resistor 10Mom is good. I test them separetly. I need to know, how the good HY3131 work.
The return of the device is expensive for me. Other function work satisfactorily for me.
Kleinstein:
The resistor reading seems to change with the meter taken of the ground. This could indicate something like a problem with EMI or maybe too much mains hum.
davebb:
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
theHWcave:
The meter was running the whole day today using the BM235 K-type probe with its sensor next to a PT100 which was connected to the 34401A. I recorded the values from both every 30s over almost 10 hours. The XDM1041 was consistently about 1.8 deg. too low but followed the temperature variations exactly. This was using the lowest backlight. When I plugged the same K-type into the BM869S (without changing anything else) it showed about 1 deg lower that the 34401A's PT100 reading. So I would say 1 deg error due to the K-type probe itself (totally expected) and 1 deg due to the XDM1041 thinking the ambient temp. is higher than it is. Although backlight is low, some things still produce a little heat and it builds up because there is very little airflow. Next step (weekend probably) is to widen the cooling vents in the DDM1041 and see if I can get the internal temperature lower.
The PT100 is another story. I have a proper 3-wire one from RS-Components so reasonable quality. Not sure if you are familiar with 3-wire PT100 but basically you need to eliminate the resistance of the wires to the sensor head. PT100 is using resistance and 100 Ohm = 0 deg. C. The change in resistance is very little from 100 to 110 Ohm is the equivalent of 0 deg C to over 25.5 deg C so you can see that milliohms count here. There are special circuits for 3-wire probes but I am using the fact that 2 wires are connected at the probe end. So if you use these and measure the resistance you get a value of 2x the resistance of the length of the probe cable. I use that to null the meter and then replace one of the wires at the meter with the 3rd one (that goes through the probe). And this is where the XDM1041 fails. You can null the PT100 probe in resistance mode, no problem. But when you go to Temperature mode and select PT100 it ignores the REL value for resistance and shows the value that includes the wire resistance. REL in Temperature mode nulls the temperature value not the resistance. Using PT100 on a XDM1041 iin temperature mode is useless unless you use an extremely short or very thick cable to the sensor head. I mean that is doable but why? The alternative is to use the PT100 in resistance mode (with proper null of cable resistance) and convert the resistance to temperature by hand (or script when reading from SCPI). This is by the way exactly what I have done for the 34401A because the 34401A has no PT100 mode so I am simply reading the resistance and convert that using the PT100 formula as long as you go only positive (> 0 deg C) its not too complicated.
# convert ohm to deg.C using PT100 probe
def PT100(ohm):
TC = 0.00385
A = 3.9083E-03
B = 5.775E-07
R0 = 100.0
return (-A + math.sqrt(A*A - 4*B*(1-ohm/R0)))/(2*B)
Does it do the 10 minute - cold-junction update in PT100 mode? I have not tested it but I am almost sure it doesn't. I mean it may still do it in the background but since PT100 does not need the ambient temperature it should not show. But I will test it tomorrow and report
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