| Products > Test Equipment |
| Hantek CC-65 AC/DC Current Probe Teardown and Testing |
| << < (27/33) > >> |
| DaneLaw:
Also got one of these CC65 and been positively surprised with this unit, my first Hantek product. Purchased the 4 cheapest AC & DC current probes I could find in China at one of their pre-NY-sales and some of them could likely work great with a new Micsig scope I had just purchased at the start of 2020.. So I ended up with 4 budget AC/DC current probes, and saw it as cheap entry tools to learn from, and compare one to the other and get an idea of frequency-rating and the noise and all that jazz.. The total price' a tad over 100 bucks' and it were more or less the same ballpark f I should have purchased Fx a Hantek CC65 inside Europe from a regional seller with danish +25%VAT. ETCR007AD 100KHz (was the most expensive at 45USD delivered it has a +/- wheel on the side, while the Hantek have a degauss-button) Hantek CC65 35USD 20KHz AllSun EM264 25USD ?? Hz (dedicated zero button, like the Hantek CC65) HoldPeak HP605A 13USD ?? Hz All 4 were AC+DC --- End quote --- --- End quote --- ETCR007 at the top waveform and CC65 at the bottom. (spotwelder) --- End quote --- The Hantek CC65 of the 4 AC/DC current probes' got way the cleanest signal.. the other AC/DC like 605A and the EM264 is primarily for DMM's and quite high amps. Here a vid with the 13USD Holdpeak AC/DC 605A https://i.imgur.com/yUrAeXz.mp4 and here the 20KHz Hantek CC65 below and the 100KHz ETCR007 at the top.. noisy to say the least.. can be seen when going full BW like I have on the CC65 at the bottom.. (load is a USB colorchanging RGB diode with like +/-150mA.) https://i.imgur.com/Cj2B5AJ.mp4 But its very likely Im doing something wrong (rookie) but so far the Hantek CC65 has been the one I been most satisfied with, and to an extent that I even wondered about getting the CC650 but the noise will be that higher, and most of my use-cases are in the lower amp-segment so decided to pass on the CC650 but CC65 have been a pleasant first purchase from the brand "Hantek". |
| dcac:
--- Quote from: toli on April 02, 2021, 01:23:06 pm ---1 - My first guess would be that the value of C15 is off and its actually much lower in capacitance. Even then, it can probably be omitted completely after the mod. If we assume ~100pF load (cable + scope input) and R18 of 1K its a pole at 1.6MHz already, so adding additional capacitance will limit this further. R18 can probably be made smaller in value quite a bit (say 330R) to push out the pole its creating with the load capacitance, which would allow extended BW. --- End quote --- Yeah I probably missed C15 when I measured the other caps - the 100nF value is just an arbitrary value from the first versions of the schematics. And I also notice neither R18 or C15 was included in the spice simulation I did here: https://www.eevblog.com/forum/testgear/hantek-cc-65-acdc-current-probe-teardown-and-testing/msg3158118/#msg3158118 Adding C15-R18 to the simulation it will actually cause some signal peaking as C15 'steals' part of the signal from the feedback loop. And question is still what exact value C15 is - I agree 100nF seems pretty big. |
| dcac:
Measuring C15 + the output cable which sits in parallel - it seems to be about 3nF. I used the same technique as I did before using a low level sine wave at 10mV RMS and measuring the -3dB point it forms as a RC network with a known resistor value. Below is the simulation with R18-C15 added - it didn't make that much difference in the frequency response. Though there is peaking of about 3.1dB at 100KHz. The lower blue trace is with C15 set to 0nF. |
| toli:
Thanks for the reply, 3nF sounds much closer to expected value as this will add a pole at around 50KHz. The peaking is probably due to stability of the feedback network now that this pole is there. It should improve peaking if you move the feedback to the other side of R18 which is the opamp output. |
| dcac:
Not quite sure what you mean about moving the feedback. I any case the schematics with regard to R18 and C15 placement seems correct. I haven't opened my cc-65 again but i.e. loading the output with a 1K resistor the signal level doesn't drop - suggesting R18 is inside the feedback loop. And adding capacitance in parallel with the output (and in parallel with C15) causes additional peaking or in other words an increased level at increased frequency. This scenario is of course only valid until the opamp saturates. |
| Navigation |
| Message Index |
| Next page |
| Previous page |