how to measure current on a circuit board without breaking any connection???

[ffira]

Can anybody tell me how to measure current on a circuit board without breaking any connection? that is, is there any way to get the current readings by just, maybe, tapping a probe, without having to insert the measurement tool in series with the circuit?

 

[MrAl]

Hello,


It is well known that a current passing through a conductor generates a
magnetic field and so measuring that magnetic field can tell you how much
current is passing through that conductor. This is sometimes done with
a hall effect device. The device (ic) is mounted close to the conductor
and the field is measured and converted into a voltage and that voltage is
measured, thus giving an indication of how much current is flowing.
The thing is though, this technique usually requires some sort of calibration
to get the readings right in the first place. This is done by passing a known
current through the conductor and adjusting the reading.
There are other problems that come up however, such as how close other
conductors are to that main conductor and so it doesnt work out very well
sometimes. This usually leads to using a magnetic core where the conductor
is passed through the center of the core and the field is measured with a
hall device inserted in the magnetic path. This usually means breaking the
main conductor too though.

Since it may be very hard if not impossible to do this unless you have control
over the board design, perhaps you can tell us what exactly you want to measure
and why you want to measure it and what kind of board it is and we might be
able to help you to measure this in another way or using another technique
or even another approach to the problem.

 

[j.friend]

If you circuit has a switch in it you could use your multimeter to complete the circuit (whilst the switch is off position) in order to measure the current.

 

[Mickster]

You could measure the voltage drop across a shunt resistor already in series with the power supply.

 

[ffira]

Ideas?

I'm actually using a wireless sensor module by SENSINODE, N710. the problem is i don't have any access to the schematics. So i'm hoping for ideas, or recommendations on how i could get the current and power readings. Maybe there's a device that could easily read the current, can anybody recommend the device and brand?

And erm, mr Mickster, to whom are u addressing that STFU?

 

[crutschow]

Are you just trying to measure current used by the device, or the current used by individual components in the device? What is the purpose of this measurement?

 

[Mickster]

I'm actually using a wireless sensor module...

And erm, mr Mickster, to whom are u addressing that STFU?

It's a forum signature, aimed at those who like to stamp on other members ideas, without offering a single bit of help.

Some like to use quotes from famous people, or make up their own, others like to post links to their own website etc.

Some find humour in the wording within a thread and use that as a sig.

e.g. Krumlink ( Electronic Circuits Projects Diagrams Free - View Profile: Krumlink ) was drawn to this piece of text:
https://www.electro-tech-online.com/threads/very-small-transmitter.25583/#post176915
...and now uses it as his sig.
Read the last line of the above post, in capitals. Actually, read the whole thread in it's entirety, for a bit of a chuckle. Audioguru is on top form

Regards.

 

[ffira]

Are you just trying to measure current used by the device, or the current used by individual components in the device? What is the purpose of this measurement?

I'm trying to measure current used by the device. The purpose is to record the power consumption of the device.

And by the way, thanks for the explanation Mickster.

 

[crutschow]

What is the power source? Can't you just connect an ammeter (DMM) in series with this source to the circuit?

 

[the eagle]

you can do that with Ohm law

 

[Mikebits]

I'm trying to measure current used by the device. The purpose is to record the power consumption of the device.

And by the way, thanks for the explanation Mickster.

Perhaps you can read the data sheet of the device in question, the data sheet should offer current consumption info. This is the purpose of data sheets.

 

[ffira]

thanks for all the suggestions.

at first i thought i don't have any access (to modify) the circuit. but after checking carefully, i might be able to connect the circuit to self made circuit so that a shunt resistor can be placed series with the circuit.

thanks a lot.
all of u are real life savers!