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| BM235's strange V and mV value |
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| Pfriemler:
--- Quote from: Fungus on April 25, 2023, 01:35:39 pm ---What meter was it? I wouldn't mind a very high Z meter... --- End quote --- edit: damned, link does not work ...? UEZNIRN PM8225: https://www.amazon.de/Multimeter-Spannungsmessr-Strommessger%C3%A4t-LCD-Anzeige-Hintergrundlicht/dp/B0BFLDDSVC Only for the 400 mV. I wish, I have a 20V or so ... btw: this was my reason to look for an hi-z meter: https://www.eevblog.com/forum/beginners/how-to-measure-in-meg-ohm-voltage-dividers/msg4612876/#msg4612876 |
| Neutrion:
Fungus: It never hurts to have yet another meter. We are waiting for your review! ;D |
| Pfriemler:
--- Quote from: Neutrion on April 25, 2023, 03:54:43 pm ---Fungus: It never hurts to have yet another meter. We are waiting for your review! ;D --- End quote --- well, in fact I consider to re-buy it just for the hi-z feature. 16 Euros incl. shipping. Did a hires pic from the inside. But this is offtopic here ... |
| Kleinstein:
With moving the probes around, it is quite easy to pic up electrostatic charge and possibly create extra charge from triboelectricity or piezo electric effects in the probe cables. So that behavious is normal, even with 10 M input impedance. A few handheld DMMs offer very high impedance in a mV range (e.g. up to some 200 mV or 600 mV). With higher grade bench meters high impedance is common, but often only to some 12 V. 20 V high impedance is less common (e.g. Sigilent 3065 or Rigol 3068 or Keithley 2001+2002). This usually needs a supply up to this voltage - so nothing to expect in a handheld meter. |
| EEVblog:
BTW, these "ghost voltages" are so much of problem for electricans on mains wiring (due to capacitive coupling), that any decent electrican multimeter has a Low Z (low impedance) mode which instead of the usual 10M input impedance, it has only a few k ohms impedance. Your BM235 has this mode. So when you are working on live wiring you don't read a "phantom voltage" like that 100V, thinking the line is live when it's now. The low impedance will ensure that the meter reads zero. |
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