Peaktech 4250 calibration

[Phil1977]

Hi,

has anyone tried to recalibrate the Peaktech 4250? It´s design is very similar to the Hantek CC-65, but not the same.

Anyhow, it has 6 7 trimmers, it would be perfect to know their function.

My own unit is not so bad that I want to do "trial-and-error". It´s working quite good as a scope clamp up to 50kHz, I don't see any bad linearity or frequency response issues, it just always measures 8% too high in the low range.

Thanks a lot in advance!

[Tjuurko]

You need to look for a variable resistor, which is connected to the 10mA/mV switch.

[Phil1977]

Thanks a lot Tjuurko, you have made a simple current clamp very happy!



These are the gain trimmers for 10x (10A/V) and 100x (100A/V). The 10x-trimmer seems not be independent of the 100x, so you have to calibrate 100x first.

[J-R]

I found some information for the CA60 version of this.  I am going to give it a whirl this weekend.  But here is the gist of the procedure as I understand it:

- Set clamp to 10mA/mV
- Adjust VR7 for zero
- set calibrator for 200mA DC and loop wire 5x through clamp (1A)
- adjust VR6 for 100mV indicated on DMM

- Set clamp to 100mA/mV
- Set calibrator for 2A DC and loop wire 5x through clamp (10A)
- Adjust VR2 for 100mV indicated on DMM

- Set clamp back to 10mA/mV
- Set calibrator for 200mA DC and loop wire 5x through clamp (1A)
- Adjust VR1 for 100mV indicated on DMM

I don't see anything about AC readings.

[Phil1977]

I did a few more tests with this device:

First, linearity before and after calibration:



It seems calibration is already off by 1% again after the weekend but all in all I think this more than okay for a clamp measurement. I do not have a Tektronix or Fluke available right now, else I´d love to compare.

Then, I did a quick test about frequency response. It was done with a waveform generator feeding a 12Ohm-resistor and a scope measuring RMS on the resistor and RMS of the current clamp. The plotted value is the deviation of the measured current to the calculated current by Ohms law. Current level for this test was only around 60mA RMS because of the limit of the waveform generator.



I wouldn't give the values over 100kHz to much confidence due to the setup. But it seems this clamp is quite okay to measure RMS up to 25kHz and resolve current spikes down to the microsecond range. I´m quite happy with this result.

This frequency response shows that a separate AC calibration is not necessary. If you connect this clamp to a RMS multimeter, then the DMM cares about the "rectification". In the mains frequency range the deviation will be quite low.