Does anybody know how to make a current probe be sensitive with low current?
I have tried current transformer and Hall effect sensor but neither of them is sensitive with low current ( below 1A ).
I saw some old post in this forum says magnetic tape head is very sensitive with low magnetic field, but i don't know if it is suit for current measuring.
And does anybody know what is magnetic resistance?
I hope somebody could know something about these.
Thanks!!

 

if you use one of those current transformer probes. The ones shaped like a donut or ones that you 'clamp' on to a wire. The reading can be multiplied for increased resolution. To get ten to one, just make the wire 'go through' the opening 10 times. In other words. make a ten turn coil on the donut. Now a 100 mA current will read out as a 1 amp current and give your readings a whole decimal place increase in resolution.

(Note: this also multiplies any error in the readings by 10)


A one hundred turn loop would give you a 0.10 Amp reading with just 1 milliamp of current flowing in the wire.

 

Does anybody know how to make a current probe be sensitive with low current?
I have tried current transformer and Hall effect sensor but neither of them is sensitive with low current ( below 1A ).
I saw some old post in this forum says magnetic tape head is very sensitive with low magnetic field, but i don't know if it is suit for current measuring.
And does anybody know what is magnetic resistance?
I hope somebody could know something about these.
Thanks!!

Are you trying to measure AC or DC current? Are you looking to detect that the current is present (>100ma) or do you need to know the actual magnitude of current present in the conductor?

hgmjr

 

if you use one of those current transformer probes. The ones shaped like a donut or ones that you 'clamp' on to a wire. The reading can be multiplied for increased resolution. To get ten to one, just make the wire 'go through' the opening 10 times. In other words. make a ten turn coil on the donut. Now a 100 mA current will read out as a 1 amp current and give your readings a whole decimal place increase in resolution.

(Note: this also multiplies any error in the readings by 10)


A one hundred turn loop would give you a 0.10 Amp reading with just 1 milliamp of current flowing in the wire.

I am doing this now, but this is not the way to solve the problem and in my real application the wire will be very thick so it is not practical to wrap many turns for the primary. there can only be 1 turn for primary winding...... so i need a way to really solve the sensitivity problem~

 

Are you trying to measure AC or DC current? Are you looking to detect that the current is present (>100ma) or do you need to know the actual magnitude of current present in the conductor?

hgmjr

I am now measuring AC current from 50Hz to 5000Hz, but the best for the application is for both DC and AC. I want to know the actual magnitude of current present in the conductor~

 

Take a look at the data sheet for this sensor - http://www.melexis.com/Sensor_ICs_Hall_effect/Linear_Hall_ICs/MLX90251_85.aspx

 

Hello,

Take a look at this application note.
It explains a lot about the current, wire distance and related field.

Bertus

 

(Note: this also multiplies any error in the readings by 10)

A one hundred turn loop would give you a 0.10 Amp reading with just 1 milliamp of current flowing in the wire.

Can you show us an example?

If the error in measuring the 1mA is 5%, what will be the error if 100 turns are use?