Products > Test Equipment
OWON XDM1041 the unknown multimeter...
BugCatcher:
theHWcave
Received my XDM1041 a few days ago (running V3.0.1 SW). During waiting for delivery was enough time to screen all available information.
Found interesting discussions regarding different types of temperature sensors.
Regarding PT100 sensors I found following arguments:
- calculations for temperatures < 0°C are more challenging
- unwanted cable resistance is adding huge errors at low temperatures (around °0C)
Regarding temperatures < °0C:
Calculation requires 3rd-order polynom (pos. temperatures only 2nd-order)
What happens when we simply ignore the 3rd-order coefficient "c"?
at -100°C an additional error of 0.2°C
at -50°C an additional error of 0.02°C
-> see first diagram ... (including tolerance band for class A sensors)
=> extreme unlikely that "home lab" applications will ever face temperatures below -50°C
=> second order correction is sufficient! No need to block calculation for <0°C!
Regarding impact of cable resistance:
I calculated the impact of an given resistor (0.262Ohm). Precise calculation based on the 3rd order polynom.
- impact nearly flat, no singularity around 0°C
- simply subtract 0.7°C for a "good enough" correction (rule of thumb: subtract 2.6°C per Ohm, perfect at 50°C)
-> see second diagram
-> there is no problem for bench applications without extreme cable length
During ordering PT100 sensors I found that there are also PT1000 devices!
Price for class A PT100/1000 unpacked sensors is below 2€ (e.g. Reichelt in Germany)
-> PT1000 reduces the impact of the unwanted resistance by one magnitude (green line)!
Problem:
XDM1041 is not supporting PT1000! ... Why? It's a huge benefit with nearly no effort (measured resistance divided by 10)!
The only solution is an external PC-SW with a very simple modification of the PT100 algorithm.
e.g. XDM1041 utility from theHWcave ... btw: this is an impressive piece of work!!!
Another idea: SW-feature to enter the cable resistance manually (no need for a 3-wire cable!)
... only need for a one time resistance measurement at known temperature (e.g. 0°C ice-water)!
I tried to install the utility on a Windows10 system running Python 3.10 ... I failed!
What must be preinstalled? Did it ever work on Windows10?
Regarding comparison of Thermocouple/PTxx ... I found an interesting link:
https://tmseurope.co.uk/applications/thermocouple-rtd-colour-codes-tolerances
-> Below 400°C PTxx class A shows always the best precision!
My own preference is PT100/1000:
- low price
- good performance
- heading for PT1000 with external SW
- full precision after cold start ... no trouble with reference junction block
- only negative point: TCs can handle higher temperatures
theHWcave:
For anyone interested, I have put the OWON Windows tool to upgrade the firmware of the XDM1041 as well as the firmware version OWON sent me (apparently V2.1.2 however it shows as 20210525) on my github page. The tool should be able to upload other firmware versions as well.
You can download it (in binary chunks) here: https://github.com/TheHWcave/OWON-XDM1041 with instructions in the readme file to reassemble the .ZIP file
(the reason for breaking it into chunks is the file size limit on Github)
To be clear, this is OWON's software but they gave me permission to post it. Don't complain to me about the quality of either the upgrade tool or the firmware please ;D
From the same place, you can download my own software (happy to accept suggestions on that) to log data from the XDM1041 on a PC (Linux or Windows), including a mode to properly use a PT100 sensor to measure temperature.
BugCatcher:
XDM1041 Continuity Test
I had the impression that the response time is related to the XDM1041 "beep-threshold".
All existing evaluations regarding "speed of continuity beep response" are based on "hectic moves" combined with gut feeling!
I would like to propose an objective test method
- a function generator (square wave, 1Hz, variable duty cycle)
- a "contact" controlled by the function generator
there are two options
- a FET, I used a 2N7000 (2.1Ohm on resistance)
- a reed relais (typ. 0.15Ohm on resistance, switching time about 1ms)
- I also increased the "on" contact resistance by adding different serial resistors (10, 30, 100Ohm)
Measurement procedure
Increase the "on" time by changing the duty cycle of the square wave
- first you hear single beeps (not every second)
- increase "on" time until you hear every second a beep
-> this is the minimum time for the reliable detection of "contact"
The diagram shows my results for the XDM1041
- response time is heavily impacted by the "threshold resistance"
- high threshold gives you very fast response
- the setting of the threshold value depends on your application!
I tested also an UNI-T 804
- fixed threshold (40Ohm)
- 2.1Ohm 180ms
10Ohm 170ms
30Ohm 170ms
What about other multimeters? Now we can compare!
Conclusion: no longer need for "hectic moves"
HKJ:
--- Quote from: BugCatcher on January 04, 2022, 01:41:33 pm ---All existing evaluations regarding "speed of continuity beep response" are based on "hectic moves" combined with gut feeling!
--- End quote ---
Not really, I have reviewed a lot of multimeters where I used something similar:
More about it: https://lygte-info.dk/info/DMMTesterACSwitch%20UK.html
My Reviews: https://lygte-info.dk/info/DMMReviews.html
BugCatcher:
Good News: XDM1041 Recording Function
XDM1041 running V3.0.1
DMMEasyControl, Version 1.7.0 running on Win10
Local recording and upload of data
- local XDM1041 recording is working
- DMMEasyControl supports upload from XDM1041 to host (slow speed, takes time)
- import of uploaded data into spreadsheet (OpenOffice)
special characters for °C, °F and Ohm are a challenge
my solution: open data-file with text editor, copy "strange characters",
past the "strange characters" as "separation characters" into the import menu of the spreadsheet,
not elegant ... but working!
Data retention
- power off, 1h later, power on: recorded data still there
- disconnected power cable, disconnected usb-cable, reconnected power (30min later): RECORDED DATA IS STILL THERE!
didn't invest more effort to evaluate max. storage time
Big question:
Will OWON also support PT1000 ??? Hope they are reading this thread ;-)
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