Micsig CP1003/CP503 100MHz/50MHz Current Probe

[amar87]

Yes, will try again with the clamp in the locked position, i also think i am doing something wrong. Will do some more measurements when i have time. I want to get to the bottom of this.

I have been thinking also the following : maybe 1 Vrms /50R = 20mA  and it is exactly on the edge.

 

[Martin72]

Please do that, the Micsig is still of interest because it is simply very compact compared to a Tektronix combi.

[amar87]

Aparently when having too many pictures inline the forum doesn't display the message correctly for some reason second time i write this .....

I tried to check my setup first:

_Wim_ suggested to see first if the bode plotter is ok so here we go:

- CH1 1 Meg
-  CH2 50R
- Used the 'butchered' BNC





We notice a 0.6 dB increase at 25 Mhz compared to the rest of the frequency range.

Next i replaced the 'butchered' cable with normal BNC RG58



The response i a lot flatter.

[amar87]

I wanted to see what happens if the probe will just stay on the coax.... so don't ask why



Something weird happens now this is a scope problem but however maybe it give a clue on the issue

Ran the bode plotter 2 times first run gives this:



Second run:



I can't explain the 3 dB shift. This is related to what _Wim_ said in a previous post.

But my conclusion so far is having the probe on the coax does not change the frequency response wanted to see just in case.

[amar87]

Sorry for writing so many messages but i put everything in one and it somehow wasn't displaying correctly so i had to delete it.....

After all of the above ran the test again this time with the probe inserted trying to figure out the reponse from the probe up to 25 MHz.



Probe is locked this time:



Displays 20 mA = 1 Vrms / 50R :




And it give this bode plot (i also placed markers ):





So i have reached the limit to what i can test.....  the thing is not flat or my scope measures crap, but i don't know if  the 2 dB should  be right.

[amar87]

There is a Whatspp number on the Micsig website. i wrote to them they also said it can be the slider. I gave them the forum link and invited them to comment as well, maybe they will do.

[Martin72]

Your pictures are always opened separately, which is a bit tiring when the post is gone and only the picture is visible.
I think the small increase that can be seen in the "cable test" is negligible, so the graph from the currentprobe is "real".
Micsig should really take a look at this, the currentprobe is too expensive for that.

[amar87]

Fo the sake of completeness i also did an 'ugly' bode plot manually:

Generator set to 50R output impedance, probe sldier closed.

The scope is set to 1 Meg input for CH1 where the output of the probe is, 50R CH2 where the generator goes.



Gives this :



Welll..... i gues if you would imagine that that part i circled in blue would be flat like the yellow line, it can be like in the datasheet...

Yes would really be nice if micsig would say something about this..... 

[amar87]

how to place the pictures so they open inline (sorry for the forum-noobness)?

[Martin72]

Hi,

I have recreated your test with the cable only, it's just like that, no need to worry.
It depends on the cable and the internal generator does not necessarily have to be ultralinear.

[Martin72]

how to place the pictures so they open inline

One possibility is to use the default setting (end of post expendable thumbnail).

[amar87]

Before i put the setup away i thought i would do some pulses through it and see what it does. 

they say Delay ＜ 30ns（6A ) i kind of get 2x this much. this delay should be the delay between the input current and the output voltage.

CH1 is the probe output.
CH2 is measuring the voltage from the signal generator.   

Using the Skew Measurement and the cursors i get 69 nS.

Is that delay parameter from the datasheet something else or am i measuring something wrong?

[amar87]

I made a mistake in the previous post i had that deskew delay set in one of the channels of the scope.  the delay is 15 nS which is lower than 30 nS so well in spec...

[Martin72]

Ah, very good.
Do you have access to a (very)fast risetime pulse ?

[amar87]

what you see there in the rigol screenshot the 7 nS is the fastest i have......

[Martin72]

OK, not..

I have just asked Batronix if they would lend me a CP1003B for testing.
Then I could make additional measurements and check it´s frequency response.

[_Wim_]

I wanted to see what happens if the probe will just stay on the coax.... so don't ask why

(Attachment Link)

Something weird happens now this is a scope problem but however maybe it give a clue on the issue

Ran the bode plotter 2 times first run gives this:

(Attachment Link)

Second run:

(Attachment Link)

I can't explain the 3 dB shift. This is related to what _Wim_ said in a previous post.

But my conclusion so far is having the probe on the coax does not change the frequency response wanted to see just in case.

I am not sure how the bode plotting function on the siglent works, but the voltage show on channel on does differ from run 1 to run 2. I would however expected this bode plot to be zero dB gain or -6dB in gain (due to the 50 ohm input), I do not understand where these positive gains are coming from as they is no amplifier in the cable. Could it be that the "reference" and the "test signal" are swapped? Normally I expect a bode plotting function to report the difference in gain between the reference input and the test input, and in the case of only a BNC cable between the two, this should not create any gain...

[Martin72]

My previous "only cable test" I did several times, always with the same result.

[amar87]

i had the probe input on 2x on channel 1 that is where the 'gain' is comming from.... sorry for the confusion.... The scope leaves it like that if you change from current to voltage. I just did not bother to change it.

[Martin72]

I have just asked Batronix if they would lend me a CP1003B for testing.

Not, but they suggested to "buy" it and return inbetween 30days.
And that´s what I did, should arrive in the next days.

[Martin72]

Batronix, fast as lightening, as ever...

[amar87]

Cool! Let's see how it tests. 

[amar87]

did yours come with an EU style power adapter?

[Martin72]

Hi,

Yes, with this one:

https://www.knivesandtools.de/de/pt/-qualcomm-qc-3-0-usb-adapter.htm

Let's see how it tests.

I'm also very curious, but I'll wait until tomorrow because the package was very cold.

[Martin72]

Well...
Here are a few results, I would still like to measure the risetime and accuracy.
The noise is good, the delay is very good, but the linearity leaves a lot to be desired.
Fluctuations of +/- 0.5dB, as with the Tek Probe, are still acceptable to me, but this...
I'll try a few more things at the weekend.
As things stand now, I wouldn't want them.