# measureing current across the resistors

Discussion in 'General Electronics Chat' started by Avicreats, May 29, 2013.

1. ### Avicreats Thread Starter New Member

Jan 18, 2013
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0
Hello everyone,
I hav attached a signal conditioning circuit.The source is 1amp ac current source.Plz can u tell me what will be the voltage to the input of non inverting amplifier if the values of resistor are
R6=1 ohm,10watt(for current to voltage conversion)
R1=1k
R5=1k
R3=10k
R2=10k.

thank you,

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2. ### t_n_k AAC Fanatic!

Mar 6, 2009
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This isn't going to work very well. With a 1A (Sine wave RMS) current in a 1Ω resistor the peak voltage developed across the resistor would be around 1.4V. The bridge rectifier will require around 1.4V just to get the diodes into conduction. So the bridge output will be very small and will not accurately reflect a linear relationship between input current and output voltage - such as you presumably require.

You might consider an op amp based "ideal" rectifier as the front end of the transducer circuit.

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3. ### Avicreats Thread Starter New Member

Jan 18, 2013
19
0
increasing the resistor from 1ohm to 3 ohm can make this circuit work?

4. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,166
775
What voltage is coming out of the current transformer coil?

5. ### #12 Expert

Nov 30, 2010
16,705
7,358
I believe this one is about a current transformer. The load resistor determines the voltage because the current is forced to be the right current. I have a drawing. I'll look it up and BRB.

The current transformer is in the bottom left corner, complete with precision rectifier. Can you pick it up from here?

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6. ### Avicreats Thread Starter New Member

Jan 18, 2013
19
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Thank you t_n_k.
I googled for an ideal opamp rectifier and i got was with dual supply opamps.(lm741). But i require a single supply operating ideal opamp rectifier.
Can u help me finding out this
Thank you..

7. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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Attached a non-optimized solution with a single power supply. Using LM324 so it could all be done with the one IC.

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8. ### Avicreats Thread Starter New Member

Jan 18, 2013
19
0
Thank you,
Il check this out...

9. ### Avicreats Thread Starter New Member

Jan 18, 2013
19
0
I worked with the primary part of th circuit that u hav attached i.e,only the rectifier circuit and i connected (+24 0)v directly to opamp lm358(didnt had lm324). But it didnt work as expected.the current input was 12mA and i was getting noise as output ie -9mv and floating..is there any way to get through this problem..
Thank you..