We are trying to monitor motor currents. High accuracy is not required. We are thinking of using cost-effective hall-effect current transducer. But the output is 0-5 Vac/60/50Hz. Can we just use 0-10 Vdc analog input here ? If yes, what can we get ?

 

Sounds like your sensor was designed to connect to an analog panel meter, or it is actually a 0-5 amp (not volt) output? Dont connect your AC output to a DC input device, there are fundamental differences in the way AC or DC is measured. You will either have to install a signal converter, or buy a transducer that has
0-10 volt outputs. Try Ohio Semitronics "http://www.ohiosemitronics.com":http://www.ohiosemitronics.com or Load
Controls Inc. "http://www.loadcontrols.com":http://www.loadcontrols.com

 

Why don't you just rectify 0-5 V ac by a simple diode bridge and get 0-7 V dc?

 

> Why don't you just rectify 0-5 V ac by a simple diode bridge and get 0-7 V dc?<

I would not advise just rectifying the AC for a DC input because the rectifier output will have a ripple which can give you an erroneous reading as your analog input D/A converter samples the input at intervals that are not synchronous with the ripple.

 

Yes. But you are losing half of your available input range on your measurment device. A better way to go would be to get a transducer unit that
matches your voltage input or get a unit that has 0 to 1ma output and scale it using a load resister on your measurement device.

Regards
Erich Mertz
[email protected]

 

From: <[email protected]>
To: [email protected]
Subject: RE: ENGR: Use 0-10 Vdc Ai for 0-10 Vac signal

....and put in a capacitor and a resistor parallel to the input (after the diode) in order to get some basic filtering....


/Johan Bengtsson

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You can filter the ripple by a capacitor. The author wrote that high accuracy is not needed, thus I think this is a cheap and simple
solution, but does not sense between 0-0,4 volts (using 2 Germanium diodes).

 

There is nothing worse than a half baked kludged together instrumentation system. If your going to do one at all do it right and get the
correct kind of transducer or signal conditioner in the first place. The poster apparently has not yet purhcaed the unit, so he may as well
get one that will work out of the box to begin with and save some future headaches.

 

it looks to me that the ct u r thinking of is pretty much the same as the type of ct we used to use (and still do) all the time. if you look
closer, you'll probably find that the output from it is 0-5 Amps and not 0-5 Volts as you stated (i've never heard of a ct with 0-5V output
but then everyday's a schoolday or so they say!)
Anyway, we use a converter by a company called palladin ([email protected] OR just palladin.com).
It gives you a 0-10VDC or 0-20mA output from 0-5A
input (depending on which you specify when ordering) which you can then use in a more manageable format as an analog input to a plc for
instance.
I have no connection with this company but can highly recommend their equipment as in 15 years i've only ever known one of their units to
fail.