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Micsig CP1003/CP503 100MHz/50MHz Current Probe

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Martin72:
Hi,

https://www.eevblog.com/forum/testgear/micsig-cp1003cp503-100mhz50mhz-current-probe/msg5275105/#msg5275105

See the noise picture, try to recreate it with the settings you can see in the picture.
Then:
You're not triggering on channel 4, I'd change that if I were you.

Kean:

--- Quote from: folays on October 25, 2024, 03:10:55 pm ---Hi, I've bought a brand new CP503B, is having only XX mA precision on a constant DC 30V / 2A normal ?
Here below are the probe in the 6A range (correctly in the lock position !) when power supply is OFF, then ON.
As you will see, under 2A of current, the probe measures an AMPLITUDE of 237 mA (24 mA at rest).

--- End quote ---

Do you have a 15 ohm 100 W resistor by any chance?  That way you can eliminate any extra noise induced by the DC load control loop.  You've already shown CR is noisier than CC mode.

You can use use a lower voltage if you only have lower wattage resistors.  It also doesn't have to still be 2A to get a feel for if it makes any difference.
Even better if you can use a battery as the source.

electr_peter:

--- Quote from: folays on October 25, 2024, 03:10:55 pm ---Here below is the setup of the lab power supply + the DC electronic load (which I put on a constant RESISTANCE).
Maybe I misunderstood the ability of the DC load to really maintain a stable resistance (or current) under a stable power source ?

--- End quote ---
CC mode works best, other modes (CR/CV/CP) are "indirect" with most DC loads and can produce "interesting" results.
Bottom line, use very stable current source (real resistor across PSU output) when checking stability of current probe.

folays:
Thanks for you insights ;
I'm new to the electronic hobby ; See one of my adventure here : https://www.eevblog.com/forum/repair/repairing-a-robotic-pool-cleaner-zodiac-vortex-3/

* In the above topic, for a pool cleaner robot, the propeller motor is powered at 28V and I measured the propeller motor at around 56 Ohm (disconnected, at idle).
On my desk (above water  :)) The robot would put itself in a state of "fault" mode, and I guessed that the IC board were measuring propeller consumption Amperage,
and thus was able to put itself to fault mode for safety reasons, thinking it somehow got out of the pool.
The future (yesterday) proved me right, as soon as I plugged a DC load consuming those 28V at 20-25 Ohm or less (raising Amperage to 1.5 A), the robot behaved like it were submerged.
I often told myself, as in the case above, "damn right now I would like to have a purely resistive load, 28V at 1-2 Ampere in this case, so I would need something around 20 Ohm, not the most difficult I have a box of resistances, but I mainly need it to be able to dissipate 14 Watts of energy, not those pesky .125 Watts common resistances... Welp, let's buy a DC load....".

As a newbie, I only used for now Batronix and Eleshop, but they don't have neat low-resistance multi-watts resistances.
Would you have a shop recommandation for Europe/France ?

Unfortunately, on the supply side, I don't see where I could at home find 1A of battery DC current. Car's battery I would prefer not extracting it (car electronics sometimes reset unwanted stuff like remote keys), Power tools' batteries have circuitry unless I open their assembly, maybe I could take a bunch of AA batteries in parallel, I didn't checked their per-unit Amperage.

In the post linked by Martin72, I see the user have a https://www.siglent.eu/product/1149228/siglent-df2001a-power-analysis-deskew-fixture.
It's probably off-topic and of no help, but in any case, I own the Batronix Demo board https://www.batronix.com/shop/demoboards/Batronix-MSO-Demo-Board.html.


--- Quote ---You're not triggering on channel 4, I'd change that if I were you.
--- End quote ---
I wanted to be in roll mode (continuous and rolling, not clearing-the-screen every time the horizontal span of time has been measured), I didn't yet figured out how to make Roll mode always behave like this, but I think that if I were to be (a) in Roll mode (b) set a correct channel (c) have the trigger level in the Amplitude region ; Then I sometimes have the Roll behaving like if the scope were to be in "Normal" mode (not "Auto" neither "Single") and not really "rolling", so until I understand why, when I want to "roll", I either set the wrong channel or set the trigger level outside of the Voltage amplitude.

Anyway, below are more refined scope settings, trying to copy Martin72's settings of https://www.eevblog.com/forum/testgear/micsig-cp1003cp503-100mhz50mhz-current-probe/msg5275105/#msg5275105 :
I changed the Timebase, Martin72 was at 1ms/div, I set my scope to 50us/div, and trigger to C4 "Normal" ;
Picture 1 and 2 are the same (just letting you on the (1) see the Channel settings, DC mode and BW 20M limit mode).
Picture 3 is at 10us/div.
I don't known why the "bands" are so much wide (multi-pixels height), I didn't enabled "Persistence" or something like that.

The Amplitude stills shows 144 mA.
Question is, regarding the Amplitude variation (which should be 2A stable in non-existing ideal setup), but is 144 mA which instruments are guilty ?
(a) could it be partly the CP503B but only for partially for up to 20-30mA variation ?
(b) the lab PSU and the DC load ?

Bonus question : I think that even if non-ideal, considering that the lab PSU is probably waaay less noisy than the DC load, would I be right regarding the lab PSU (SPD4036X) noise for being nearly non-existing (for being 10x much lower than the noise of the DC load), at least util then DC load is replaced by a "pure resistive load" ?

The amplitude is really sinusoidal-alike at 24k Hz, but I'm not knowledgeable enough to extract information from that.
I'm in Europe so mains is at 50 Hz (not 60), scope is 1 Ghz capable, CP503B should be able to measure up to 50 Mhz, at least 10 Mhz without huge distortions...

What I am observing here ? some ripple of the DC load ? What should I prioritize, finding a low-resistance 100 W ?
I own a broken 1000 Watts mains (230 V) resistive heater awaiting diagnostic. The resistor inside it should be around 50 Ohm I guess? And be able to dissipate... Maybe I should try that ?


Thanks & Best Regards,

EDIT : upload missing images.

folays:
Hello again, I salvaged a mains' heater 1000 Watts measured at 55.32 Ohm, so around 0.54 Ampere for the same 30 V.
Below two capture, I set the DC load (Siglent SDL1020X-E) to the same CC than expected heater's resistor (0.55 A).

(again I moved the trigger out of the voltage level, I didn't want to post-analysis, so I wanted the scope' to roll freely)


First one shows the DC load, 62 mA of Amplitude (and Pk-Pk).
Second picture shows the pure resistive load, 11.294 mA of Amplitude (and Pk-Pk).

Sorry for the disturbance  :(, it was the DC load, the CP503B works better without an electronic DC load.

Best Regards,

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