SparkFun Forums

[microera]

http://www.sparkfun.com/products/8883
Is possible to measure current WITHOUT connecting wires to IP+ and IP- ?
I mean wire under IP+ IP- connections and with current about 100mA?

[esklar81]

microera,

I'm not sure what you are asking, so I'm going to reply to my best guess: that you want to use that sensor by putting a wire that has a current you are trying to measure near the sensor, instead of running the current through the sensor.

It seems unlikely that you would get a usable signal by running the current near, rather than through, that sensor.

If your current is AC, you could pass the wire through a coil (making a transformer) and measure the current induced in that coil.

If your current is DC, you could use the same principal as is used in that current sensor, the Hall Effect. In the SparkFun sensor you mentioned, both the "current path" and the hall sensor are in the same IC. There's a description of several ways the Hall Effect can be used here.

Unfortunately for what I understand to be your application, the "bare" hall effect sensor that SparkFun sells has a switched output, not an analog output. Therefore, it can be used to detect the presence of a DC current, and even the frequency of an AC current (by counting how fast it switches back and forth), but not (at least, not easily) the magnitude of a current. If you read through the comments on that product page, you'll see mention of at least one part that sounds like it might do what you need.

The question occurs to me: Why not connect the ACS712 in series in your circuit?

If you'd like a bit more help, post a better description of your application, including whether the current is DC or AC (and the frequency if AC), whether you have enough slack wire in the system to make a few loops, and why you're looking to measure the current without putting a current sensor in series.

Happy Hunting,
Eric

[microera]

Yes! You guessed correctly!
Just thinking about the use of noncontact current sensors on the main power lines! Now I do not have any project, but I am looking for a cheap and simple solution accurate measurement of current!
It would be very good to have a wireless and contactless current measurement (AC or DC) and wireless broadcasting the measured values at a central location!
If sensor are only with "clamp" then installation is very easy!

[esklar81]

microera,

You might want to do a bit of research on the use of current transformers. They are the standard way of metering electrical usage above a couple hundred amperes, that is, for all but most residential and some light commercial installations. (For reference, 200 A service is what I had in a 3-bedroom, electrically-heated house in the New Jersey.)

I don't know what the standard technology is for monitoring large DC currents.

Eric