Clamp meters

[DetlefSchmitz]

If they were DC it wouldn't know what the voltage was.

 

[DetlefSchmitz]

But the T5 only does AC.

 

[JohnW2]

Sorry to butt in on BANS thread Would they work on 12 volt dc then

When measuring current, they measure current, irrespective of voltage (anyway, what voltage would you be talking about - between what and what?) - so they don't care whether the circuit responsible for the current they're measuring is powered from a 1V, 12V or 10,000V source!

EDit: However, that assumes they can measure DC current in the first place - which the T5 apparently can't!

Kind Regards, John

 

[JohnW2]

But the T5 only does AC.

So it seems! I did merely ask if 'they' (Hall effect meters, not specifically the T5) could work with DC!

Kind Regards, John

 

[ban-all-sheds]

they don't care whether the circuit responsible for the current they're measuring is powered from a 1V, 12V or 10,000V source!

The guy holding the meter might care...

 

[JohnW2]

Would they work on 12 volt dc then

As has been said, although meters with Hall effect sensors theoretically can measure DC current, many of them (like the T5) which presumably use such sensors appear not to be designed to. I don't know whether that means that they don't work at all with DC or whether they are just not accurate enough. Maybe someone with a T5 or such like could try?

As I said before, as with any current-measuring situation, the meter does not know, or care, about what voltage is driving the current being measured.

In case you're interested, this (click for details) is an example of a T5-like meter which does measure DC current:

There appear to be plenty of meters out with conventional ('closing') jaws which also measure DC current - one has to assume that, despite the 'closing jaws', they use Hall effect, not a current transformer (and therefore may well work with the jaws not completely closed).

Kind Regards, John

 

[ericmark]

As an auto electrician I had two clip-on/hold-on ammeters for DC, a little round one, not very accurate but within around 3 amp, good enough to check charging or even to show if brake lights were working +60-0--60 amp scale. The second had two slots to hold wire in, it was square and could measure as other one +60-0--60 amp in one slot and +600-0--600 amp in other slot, wildly inaccurate, but good enough to identify if lazy starter or faulty battery. They were very cheap.

But even the hard wired AVO digital auto electricians meter could give some wildly inaccurate readings, it showed the two way radio was using 100 amp on transmit, with 14/0.014 cable impossible it would have melted the supply cable. The idea of the auto electricians AVO was it had a low ohms per volt to stop false reading, it clearly did not work.

Every meter must have a tolerance and it is important to know the limitations. I had a clamp-on meter working on stress relief, it really did not matter if it showed 10 amp or 40 amp, all I wanted was to know if the mat was working or not, I knew the other cables around the meter would affect its reading, as with the auto electrics accuracy did not really matter. However if you want to do work where accuracy does matter then calibration is important. With GEC they took calibration really seriously, even my crimp pliers were calibrated. I was not permitted to bring my own crimp pliers or clamp-on meter to work, in fact I was not allowed to bring in any of my own tools, I was told it was because of insurance, it my hammer has a chip off it the firm has no control, but if the firms hammer has a chip off it, they can destroy it and issue another. And every calibration was traceable. Clearly all done in house, no good getting a meter calibrated if the firm doing it can go out of business.

 

[JohnW2]

But even the hard wired AVO digital auto electricians meter could give some wildly inaccurate readings, it showed the two way radio was using 100 amp on transmit, with 14/0.014 cable impossible it would have melted the supply cable.

Strange. Assuming it really was fairly clean DC, it is hard to see how a properly-functioning 'hard-wired' ammeter (particularly one of such a reputable make) could give "wildly inaccurate readings". Are you sure that it wasn't being confused by something other than DC?

Kind Regards, John

 

[abwooli]

So what is be best way on measuring currents besides breaking into the circuit

And mostly which clamp meter make and model do you guys recommend for DC & AC which would give u an accurate reading is Fluke any good

Thanks lads

 

[JohnW2]

So what is be best way on measuring currents besides breaking into the circuit.

Your only option is a 'clamp' meter or one of these 'open jaw' things like the Fluke T5 (or the Extech one I've just illustrated) which (presumably) use Hall Effect sensors.

And mostly which clamp meter make and model do you guys recommend for DC & AC which would give u an accurate reading is Fluke any good

Whilst some of the cheaper ones are probably OK, any of the big name ones (like Fluke) would be as good as anything. Bear in mind, though, as I've been saying, that many of them cannot measure DC current, so you have to look specifically for that capability if you want it. None of the 'clamp' meters using current-transformer technology will work with DC - and (as with the T5) even some of those which are presumably using Hall Effect technology do not claim to be able to measure DC current (without breaking into the circuit).

Kind Regards, John

 

[abwooli]

Your only option is a 'clamp' meter or one of these 'open jaw' things like the Fluke T5 (or the Extech one I've just illustrated) which (presumably) use Hall Effect sensors.
Whilst some of the cheaper ones are probably OK, any of the big name ones (like Fluke) would be as good as anything. Bear in mind, though, as I've been saying, that many of them cannot measure DC current, so you have to look specifically for that capability if you want it. None of the 'clamp' meters using current-transformer technology will work with DC - and (as with the T5) even some of those which are presumably using Hall Effect technology do not claim to be able to measure DC current (without breaking into the circuit).

Kind Regards, John

Thanks pal

 

[DetlefSchmitz]

The T5 may be using a Rogowski coil (qv). This allows open ended jaws without being able to measure DC.

 

[JohnW2]

The T5 may be using a Rogowski coil (qv). This allows open ended jaws without being able to measure DC.

I've never 'eard of such a thing ... I'm off to consult Mr Google!

Kind Regards, John

 

[ericmark]

Strange. Assuming it really was fairly clean DC, it is hard to see how a properly-functioning 'hard-wired' ammeter (particularly one of such a reputable make) could give "wildly inaccurate readings". Are you sure that it wasn't being confused by something other than DC?

Kind Regards, John

Note the word transmit, I am sure it was the RF causing the meter to give wrong readings, however at the time 2 way radios were common.