# Current Transducers

Trying to use a LEM ATO series current transducer. Does anyone have advice on how to connect to an analogue input?

Please post a link to the product page or data sheet for the device.

bottom line: it produces an output, which is apparently 333 mv at max current

the arduino accepts a 0 - 5 VDC analog input, which is divided into 1024 levels

you have to tweak and fiddle and adjust the 333 mv output into that 0 - 5 V range, with an amplifier that has a gain of 15 times the input

then you measure that with the arduino

pollockbilly:
Trying to use a LEM ATO series current transducer. Does anyone have advice on how to connect to an analogue input?

Yes, with signal conditioning. The current transformer has a primary current based on:
IPr = 10, 15, 16, 20, 30, 32, 50, 60, 63, 75 A

Those are full scale primary currents. The output is, as mentioned, 333 mV and that is working into a Rated burden Rbr kΩ 100. So with full scale current and a burden resistor of 100K you have 333 mV which is AC. So you need a signal conditioning circuit if you plan to use this with an Arduino ADC. Have you read the data sheet and more important understand the data sheet?

Ron

333mV AC is almost 1volt peak/peak.
Perfect to measure with the build-in ~1.1volt Aref of most Arduinos (without amplification).
If this is a transformer output, then you just have to bias the other side on 0.5volt,
with a voltage divider from the 3.3volt supply (of a 5volt Arduino).
Leo..

Datasheet is a bit confusing, alas. What they call the burden resistance is actually the load-resistance, it has
an internal burden resistor (100k is orders of magnitude too high to be a burden resistor for a CT). What
they mean is a load resistance below 100k will reduce the accuracy below the datasheet value.

I am often shocked by how bad datasheets are for electromagnetic and electromechanical manufacturers!
You often have to look out for typos, bad units, "Mv" instead of "mV", that kind of thing, this is not that bad,
although they do say 'k' for kelvin instead of 'K'.

Note that this, as with all CT transducers, is AC only.

MarkT:
Datasheet is a bit confusing, alas. What they call the burden resistance is actually the load-resistance, it has
an internal burden resistor (100k is orders of magnitude too high to be a burden resistor for a CT). What
they mean is a load resistance below 100k will reduce the accuracy below the datasheet value.

I am often shocked by how bad datasheets are for electromagnetic and electromechanical manufacturers!
You often have to look out for typos, bad units, "Mv" instead of "mV", that kind of thing, this is not that bad,
although they do say 'k' for kelvin instead of 'K'.

Note that this, as with all CT transducers, is AC only.

That was a good catch and thanks for pointing it out. I read into it as burden resistance and while I thought 100 K high for a burden resistance was very high I just let it go.

Ron

The datasheet does have a diagram showing how its wired and if you look carefully it shows both the burden
resistor, capacitor and load resistance (labelled RL for load resistance).