measuring DC

[ecowarrior]

I have to measure (full time) the amoint of DC current flowing. Its absolute max of 10Amp (absolute peak)_ but I need to feed the o/p into a data logger with 0-5 or 0-10v input. The clamps I have foiund are all for 100 or 1000 amps and very inaccurate at less than 1 amp. I am looking perhaps for a pcb mounted component that may do thios. Can anyone aim me in the right direction?

 

[ricicle]

Depending on how small the current will be be, you could create several loops of the conductor through the coils. Then divide any reading by the number of loops.

 

[viewer]

If you are sure that it is <10A then this may help. The meters are from Maplin and very cheap.
http://www.youtube.com/watch?v=7lwZkl0yBqA

http://www.amb.org/forum/diy-hacking-multimeters-for-rs232-data-logging-output-t1210.html

 

[davelx]

Deleted - answered my own question.

 

[ricicle]

Several clamp on meters measure direct current.......

 

[bernardgreen]

Try LEM

http://www.lem.com/

I used them in the past and found them easy to use and accurate

 

[JohnW2]

Depending on how small the current will be be, you could create several loops of the conductor through the coils. Then divide any reading by the number of loops.

I don't think DC current will transfer very well through 'coils' Despite the thread title and the first line of the OP, I think some have been led astray by the OP's reference to clamp meters!

Kind Regards, John.

 

[DetlefSchmitz]

Typically you have a Hall effect device responding to the magnetisation of the core, and balance out the current using a multi-turn secondary winding, using an op-amp.

The only error to worry about is is the core gets saturated and therefore permanently magnetised, so it is best to calibrate zero current every time you use the device.

+1 on the LEM transducers.

 

[JohnW2]

Typically you have a Hall effect device responding to the magnetisation of the core, and balance out the current using a multi-turn secondary winding, using an op-amp.

Goodness, one learns something every day. Thanks. I'd always assumed that they used a type of current transformer. Do all clamp meters work like this?

Kind Regards, John

 

[ecowarrior]

Thankyou all for your advice. I will follow all these up

Kim

 

[DetlefSchmitz]

Typically you have a Hall effect device responding to the magnetisation of the core, and balance out the current using a multi-turn secondary winding, using an op-amp.

... Do all clamp meters work like this?..

Just the ones designed for dc. Ac ones are as you pictured.

 

[JohnW2]

... Do all clamp meters work like this?..

Just the ones designed for dc. Ac ones are as you pictured.

What sort of proportion of clamp meters would that be, I wonder? Since it's never really occured to me that they could work with DC (because of how I assumed they worked), it's never occurred to me to look to see if they could measure DC!

Kind Regards, John

 

[ricicle]

I'd always assumed that they used a type of current transformer. Do all clamp meters work like this?

Kind Regards, John

Transformer action is only possible in ac circuits John

 

[JohnW2]

I'd always assumed that they used a type of current transformer. Do all clamp meters work like this?

Transformer action is only possible in ac circuits John

Quite. That's why I responded to your earlier post with:

I don't think DC current will transfer very well through 'coils'

... until today, it had never even occurred to me that there were clamp meters that could measure DC current!

Kind Regards, John

 

[bernardgreen]

Some AC clamp meters use the Hall affect, amplifier and counter current method as it works over a very wide range of frequency from zero upwards to over 200 Hz.