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| Will this 2V signal damage my bench multimeter over time? |
| << < (3/8) > >> |
| Amaruk:
--- Quote from: tautech on December 30, 2021, 08:45:28 pm ---Can you check again to clear any doubts please. --- End quote --- Yes, I think the manual is a bit confusing here and my statements above did perhaps not clear things up. Let me try and explain better. The only way to set the input impedance is to first set the DMM to the manual 600mV range. The default value is 10MOhm which is what my DMM was set to in this range. But you can set it to 10GOhm if you want. For all other ranges there is no option to control the input impedance (menu option goes away) as it is using 10Mohm all the time. Anyway, I set it to the 600mV manual range, set the impedance to 10GOhm, went back to the 6V manual and re-ran my test. Same outcome. Relay clicking at 2.2/2.0V. Thus, anytime you plan on measuring a voltage that is 2.2V or above (for which you can't use the 600mV manual range), the impedance will be at 10MOhm and the relay will activate as soon as it detects the voltage. For example, every-time you want to probe a 5V rail the relay will activate twice - first when you make contact with 5V rail and then again when you lift the probes away from the rail. If you do this often you will have a lot of relay action going on. And you can't avoid it... I will probably send an email to tech support and see what they say as there might be an option to turn this off that I have not found yet. |
| AVGresponding:
It might be useful to know exactly which relay is switching? Presumably these units have range relays as well as the impedance switching relay. It would be odd for either of these to be switching while in a manual range... :-// |
| Kleinstein:
If the high impendace mode is limited to the 600 mV range, it is a bit odd, that the realy switches at around 2 V and not at around 600 mV. Without a significant load to switch relays have quite a long service time and can operate some 100 million times (typical number, depends on relay type). So it makes some noise and causes some delay, but the relay still would not wear out before the probe tips or the display. One should be able to avoid the clicking noise by choosing a manual range (e.g. 6 V or 10 V depending on the meter). |
| Circlotron:
--- Quote from: Amaruk on December 30, 2021, 04:08:46 pm ---Some say that relays have a life-span of 100,000 activations. --- End quote --- Maybe 100,000 operations at full load. Some years ago I did a test on a small relay and had a micro driving it at about 3Hz and it checked that the contacts made and broke every cycle while powering a 10K pullup resistor as a load and if one cycle failed it would bring up a warning LED. The test got to 70 million cycles without a single switching failure and was still going fine. |
| Martin Miranda:
Maybe 100,000 operations at full load. same here i concur. bench multimeters are usually used in production lines. so i don't think there would be a problem. :) |
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