A tip for current measurement with DMM ?

My Fluke says 'lead' on the display when you change. Hasn't stopped me blowing a fuse though. ;-)

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Some DMMs -- such as my Fluke -- have a beeper that sounds when the switch is set to measure voltage, but the cables are plugged into the current jacks. (The opposite situation doesn't need a warning.)

N Cook schrieb:

Hi,

Have a look at

This DMM (obviously discontinued) and other types of that line of GMC DMMs have a so called "Automatic Blocking System": depending on the measuring range only the corresponding inputs can be used - the other ones are blocked.

I don't know if Gossen Metrawatt's DMMs still have this feature.

HTH

Reinhard

Same here. I've blown a few fuses in my 77.

Its not the blowing of a meter fuse that I'm concerned about. Its shorting some expensive bit of otherwise working kit that I'm wary of. I've not done it for a long time but there could so easily be some time in the future, probably pushed for time, and there will be a big flash and a bang.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I am in the happy position of having several decent meters, one of which I use exclusively for current measurements. It has croc clip leads.

It`s very rare that my favourite Flukey gets switched to amps - So there`s your answer, buy another meter just for current, fit it with croc clips to remind you do to go poking around circuit boards with it

Ron(UK)

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I take it the 2 red rings on the lower line are shutters that slide away when the probe plug is pushed into the relevant socket.

It still leaves the possibility of thinking (or not thinking) that the DMM is , per usual, set for measuring voltage but is still set for current.

So far, the only retrofit add on I can think of, is a buzzer activated on inserting the probe plug in the current socket and beeps continuously until removed.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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That seems the easiest solution, with permanent blanking off the current sockets of the one used for Vac & dc ,R , and D test only. I will see if my old Beckman or whatever it is is still working order.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Some Fluke models beep at you if you select a voltage range with the probe still plugged into the current socket.

Graham

N Cook schrieb:

...

AFAIK the input sockets for measuring current are blocked mechanically when the function/range selector is switched to voltage or resistance measurement (and vice versa): it isn't possible to insert test leads into the blocked sockets.

At the same time you can't switch to voltage (or resistance) measurement if the test leads are still plugged into the current measurement sockets.

No, it wouldn't be possible to turn the function/range selector switch to any voltage measurement range.

IMHO this wouldn't be necessary any more.

Regards

Reinhard

DMM

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The point of my post/query was that someone, like me, using the same DMM day in day out, 99.99 percent of the time for other than current, may accidently go to use this meter , still set in amps mode, for measuring volts , just because it is so ingrained in using it for such purposes.

Anyway, potential pitfall solved using Ron(UK) technique in this thread.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

further,

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A 5 minute job and peace of mind. Fluke 77 with hot melt glue down the 2 current sockets and a dollop on the rotating function switch surround. so it cannot be turned to A dc or ac.

A dollop of hotmelt in the "volts" socket of the old meter and a 2 croc-clip ended leads. instead of probes, so very unlikely to absent-mindedly use use that one in volts test mode.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Or just use some pvc tape, avoid ruining a meter, neater and cheaper, or if you want an elegant solution, you can buy blanking plugs in red and black to fit 4mm banana sockets.

Ron(UK)

Actually, it might. If you have leads plugged into the voltage inputs and are attempting to measure current in a high voltage system such as a laser power supply, the DMM will likely smoke when power is turned on. :(

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What are you saying? You blew up your meter? :) Get a industrial fluke.

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but have you considred a clamp-on probe to measure current. Fluke makes one, forgot model nbr, matches to a particular meter. The output would be a voltage you can measure with the DMM that prevented us blowing ddm when measuring currents

:Can anyone improve on the following especially reducing, even further, the :chance of mistakingly using a meter set for current monitoring on live kit , :thinking you are measuring voltage. : :Assuming others here are like me, rarely use the current function of a :DVM/DMM. :Leave a gummy bright or contrasting sticker over the ammeter socket of the :meter. When transfering the red lead to that socket then transfer the label :to the function or on/off switch. : :The ideal would be some sort of mechanical interlock but I cannot see how.

Gossen Metrawatt meters have the interlock function. If you have the RED lead in the normal V/Ohms socket the current measurement sockets are blanked off with a red plate. You can't select the current ranges on the range switch until the RED lead is unplugged. If you have the RED lead in one of the current measuring sockets (mA or A) the range switch can't be moved to any other position. Of course this doesn't stop you from trying to measure voltage while it is set up for current measurement but I find that I always check for range setting before connecting to equipment and because the switch won't move to any other position this has always prevented mishaps.

But just how accurate are they when measuring small DC current?

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    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I use the current measurement frequently, the only time I've had trouble is going back to voltage measurement after using current and even then it's rare and results only in a blown fuse.