Products > Test Equipment
Siglent SDM3045X mA current measurement - weird behaviour
ArthurDent:
I suspect that when the meter switches current ranges there may be different value current shunts switched in. Say on the 10A range it is .1 ohm, on the 600Ma range it is 1 ohm, and on the 60Ma range it is 10 ohms. (I just guessed, I don't know what your instrument has for range and shunt values). If you are putting a resistance in series with your power supply and your load, the voltage drop across the meter may be too high on the lower ranges to allow your circuit under test to receive the proper voltage. Different multimeters will have different values so one might work while another might not.
Use a second voltmeter and try reading the actual voltage the device is receiving after the it goes through the ammeter. Switch the current ranges and see what effect that has on the voltage.
tautech:
--- Quote from: ahope on November 04, 2018, 03:02:29 pm ---The meter is a bit over a year old. A few months ago I blew the internal 10A fuse which I replaced myself. Otherwise the meter has been sitting on my bench since new.
--- End quote ---
I've heard of this once before, ie. the internal fuse opening before the one on the back panel.
Do you remember the style of internal fuse, eg. fast blow, glass or ceramic ?
What is the fuse in the rear panel ?
From the datasheet:
http://www.siglentamerica.com/wp-content/uploads/dlm_uploads/2017/10/SDM3045X_Datasheet_DM0545_E01A.pdf
Internal :12 A, 250 V slow-melt fuse
Rear panel : accessible 10 A, 250 V fast-melt fuse
Which makes me question why the internal fuse should open first. :-//
Could they be installed incorrectly ?
Performa01:
If there was a probem with the fuses, there would be no reading at all. More specifically, we would not see a correct reading in the Amp ranges.
The problem has to be with the shunt resistors:
0.01 Ohm for the Amp ranges (6A, 10A)
0.1 Ohm for mA ranges (60mA, 600mA)
1 Ohm for the lowest ranges (600µA, 6mA)
@ahope, have you tested the 6mA range and does it fail as well?
If just the 60mA and 600mA ranges are off, then something might be wrong with the 0.1 Ohm shunt resistor.
If the 6mA range fails as well, then I would suspect a problem with the relays for the range switching and/or some serious contamination (lump of solder?) on the PCB.
I do not think this is a calibration issue because the error is so massive.
tautech:
OK so ahope tried what I sent him with zero result. :(
So where we are behind the scenes in discussions with Siglent.
This has been escalated to the product manager and technicians and they are checking possible scenarios.
There is suspicion of an analog board problem, yes of course and I have some ideas of just what.
Now it's Sat at the factory so we won't get a reply until Mon (your Sun).
2 immediate possibilities in my mind; damage to relay contacts or one of the shunts.
Thoughtful testing should easily confirm.
One suspects the over-current/blown fuse event caused this...........but it shouldn't have ! >:(
The 10A FB rear panel fuse should open first......not the 12A SB on the PCB. :-//
ahope, make another post or 2 to get your count above 5 so full member privileges become available.
ahope:
Hi guys,
Thanks for all the suggestions.
I ran through some more tests now, and the error is persistent from about 250mA down.
If I set it to 600mA and then gradually reduce the current it will show correct values until i go below approx 230mA. Then the relay clicks, display is reduced with about 88% and will stay that way all the way down to microAmps.
I am quite sure its a relay kicking in another shunt resistor that causes this. Question is what will cause the relay to trigger at the wrong time/current?
Still working on this, will have a look inside tomorrow.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version