# measureing current across the resistors

#### Avicreats

Joined Jan 18, 2013
19
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,

#### Attachments

• 117.7 KB Views: 51

#### t_n_k

Joined Mar 6, 2009
5,455
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.

#### Avicreats

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

#### Dodgydave

Joined Jun 22, 2012
10,050
What voltage is coming out of the current transformer coil?

#### #12

Joined Nov 30, 2010
18,223
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?

#### Attachments

• 62.5 KB Views: 30

#### Avicreats

Joined Jan 18, 2013
19
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.
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..

#### t_n_k

Joined Mar 6, 2009
5,455
Attached a non-optimized solution with a single power supply. Using LM324 so it could all be done with the one IC.

#### Attachments

• 62.4 KB Views: 37

#### Avicreats

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