Products > Test Equipment
Micsig CP1003/CP503 100MHz/50MHz Current Probe
_Wim_:
--- Quote from: amar87 on January 04, 2024, 10:34:56 pm ---But what i observed is that the error (below 20mA in the 6A range and below 50 mA in the 30A range) is mainly caused by the offset that it has after zeroing. What i also observed that this offset has a tendency to drift after zeroing. maybe some interesting experiments would be observe when it stops drifitng. Strictly speculating with the info i have at the moment this could be the the reason why they give the +/- 10Ma after the percentage.
--- End quote ---
This is typical for a probe like this. My fluke I50 also drifts after zeroing. I think you are correct that the +-10mA comes at least partly from this drift, and hence the accuracy is specified as the sum of the drift and the measurement error.
--- Quote from: amar87 on January 04, 2024, 10:34:56 pm ---I can also plug it in the multimeter witha BNC Banana adapter, but then how to compare it ? The DC load i used (Rigol DL3021A) needs to be stable. (which i have no idea how stable it is ), i could take a reading DC load on X mA in the shunt of the multimeter, then same with current probe plugged in the multimeter on voltage? Then we don't know how accurate the multimeter is on voltage vs on current. Then the sampling rate and bandwidth from the multimeter is lower than the scope.......... This makes me go crazy....
--- End quote ---
I am not completely sure why you want to do this, but if it is to rule out errors from the scope, I would just check the scope DC voltage accuracy vs your multimeter. But as you are using a 10bit scope, I do not expect here anything significant vs the 1% error you are trying to verify. For me it looks like the probe is meeting is spec for DC accuracy everywhere apart from the 2A measurement on the 6A range where it just barely exceeds it, but this could be due to tolerances in the test setup. Noise is also quite ok from the looks of it.
For the AC noise, can you put the bandwidth limit to 20MHz on your scope and report the ACrms and ACpp? This should according to the datasheet be below 1.4mArms when limited to 20MHz.
amar87:
The requested screenshots with 20 Mhz bandwidth:
6A range :
30A range 100 ms/div :
I am not sure which figure to take looking at the STDEV measurement on the scope which i think is the RMS without DC component but not sure and playing with the timebase the noise can be lower
Having 20 ms/div i get this :
Then 20 ms/div and change aquisition to average i get this:
So i don't know how to measure to verify the ≤ 1.4 mA RMS (Bandwidth at 20 MHz, Range 30A, 10X) spec
amar87:
I tried doing some bode plot using the internal signal generator from the scope that goes up to 25 Mhz but i think i am doing something wrong and don't know what but i would have expected the bode plot to be flat. I am attaching a few pictures so don't laugh.....
i wanted to see if the magnitude line is flat and does not change up to 25Mhz
Here is the test setup and the scope setup for the measurement:
In Ch1(1 Meg ) i pluuged the output from the current probe in CH2(50 Ohm ) the input from the internal generator and the red wire is also looped through the probe as much as it fits.
I have to try with more windings i thing that is why i am getting crap.
Martin72:
Assuming the generator really delivers a 3vpp level, you would have to measure approx. 21mA with just ONE winding (i.e. simply connect the clamp to the cable).
Because 3vpp is 1.06Vrms.
This voltage divided by the 50 ohms is 21mA.
The output of the clamp delivers 500mV/A, i.e. 10.6mVrms at 21mA.
That would be a factor of -40dB for one winding, you have several windings and approx. -67dB.
_Wim_:
--- Quote from: amar87 on January 05, 2024, 10:50:39 am ---The requested screenshots with 20 Mhz bandwidth:
6A range :
(Attachment Link)
30A range 100 ms/div :
(Attachment Link)
I am not sure which figure to take looking at the STDEV measurement on the scope which i think is the RMS without DC component but not sure and playing with the timebase the noise can be lower
Having 20 ms/div i get this :
(Attachment Link)
Then 20 ms/div and change aquisition to average i get this:
(Attachment Link)
So i don't know how to measure to verify the ≤ 1.4 mA RMS (Bandwidth at 20 MHz, Range 30A, 10X) spec
--- End quote ---
I would just put the scope channel into AC-coupling to avoid DC offset errors. The standard deviation is not the correct measure. Subtracting the "mean" value from the "RMS" will be closer, but I am not sure is this is mathematically correct also.
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