DC clamp on Ammeter (off topic)

cdlove23

Member
Join Date
Jun 2002
Location
San Diego
Posts
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There is some debate around the shop about clamp on ammeters and the abitlity to read DC. The qestion was brought up can a clamp on meter read DC, and the old-timers said no. The meters we have (they are quite old) in fact do not have a setting for DC. I went to the fluke site and they do sell meters that can read DC. So i did some reading and grabbed one of my older Electronics books and it says "Since transformer action is required for operation of the clamp on ampmeter only AC current can be measured. I grabbed one of my newer books and it just says switch to the DC setting.


I know somebody has an easy exlplanation here so i thought i would ask here and share it with my co workers.

Thanks!!
 
There are amprobes that can read dc amps. It is in the design and the direction of flow must be matched appropriatly. At my workplace we do have I believe its an AMPROBE brand that I would guess is 10 to 15 years old and it does read dc or ac.

I believe they work around the principle of the magnetic flux of the wire just as ac but i believe itself also produces a field and the relationship of the two is what gives the reading.
Most that I have used require "zeroing" the clamp and batteries to induce the field in the case of a clamp on for a regular meter.

As always I'm sure someone will have a little better onfo for us.


Drewcrew6
 
Yes, you can measure DC with a clamp style meter but be prepared for some inaccurate readings. In previous employment I worked as a part-time auto-electrician & have my own dc clamp meter. It reads to 400A but +/- 2A accuracy.

I have also used a Fluke clamp-meter attachment that reads AC or DC, but as mentioned above, you have to zero the meter before taking your readings.
 
The real question you are asking is:
Can I read DC Current with my "CT" type amp clamp, that plugs into my meter, the same one I use for AC amps?

NO, A Current Transformer type amp clamp will not generate a usable signal to the meter, when measuring DC current.

BUT, A Hall Effect type current sensor will. Usually A DC Current clamp will have some active circuitry in it. Thereby usually requiring batteries.

If your question was: "Can I read DC current with my brand new fluke 336 Clampmeter?"

Then the answer would be yes....
 
Thats right, it is called the 'hall effect' for measuring DC current. It usually says that on the clamp meter.
I do not know what the 'hall effecr' is, but it works just fine for me.
 
Although the Hall effect meters are the best there are some meters really for the motor trade that just measure magnet flux and often have two groves to pass wires +- 30 amp and +- 300 amp not very good but OK to set welding machines etc. Try Auto electricial outlets.
 
In a nutshell, the Hall effect is this. In the presence of a magnetic field, the electrons in a semiconductor move to one side of the semiconductor as they move. This produces and electric potential from once side to the other of the semiconductor proportional to the field.
 
DC Clamp-On

Dude, it's so simple how they work. (Good thing or I'd be outta luck!)
A DC ammeter has an oscillator circuit within it that supplies an AC signal across the DC carrying current conductor. The meter is calibrated to display the interaction between the fields as the DC current. I've found them to be quite accurate when compared against an in-line meter.
 

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