Bipolar to Unipolar Voltage Conversion Help Needed
Bipolar to Unipolar Voltage Conversion Help Needed
(OP)
Greetings All,
I need help in getting/designing a practical cicuit to convert a Bipolar (+/-) signal to a unipolar (+) signal. The particulars of the cicuit are:
I am measuring an Amperage from a wire using an LA100-P current sensor from LEM. The sensor runs off of a +-15VDC power supply and outputs a current to a measuring resister. The voltage potential across this resister is +-1.5 VDC. I need to convert this to a 0-3VDC signal that will be measured by a Texas Instruments Microcontroller. TI has a aplication note that show some op-amps doing it, but the circuit has no practical information or real values showing how this can be done. It appears that I'll need to use some op-amps to do this, but does anyone have any practical cicuit (I.E. one that has values) that they can recommend/share?
Thank You,
Gordon
I need help in getting/designing a practical cicuit to convert a Bipolar (+/-) signal to a unipolar (+) signal. The particulars of the cicuit are:
I am measuring an Amperage from a wire using an LA100-P current sensor from LEM. The sensor runs off of a +-15VDC power supply and outputs a current to a measuring resister. The voltage potential across this resister is +-1.5 VDC. I need to convert this to a 0-3VDC signal that will be measured by a Texas Instruments Microcontroller. TI has a aplication note that show some op-amps doing it, but the circuit has no practical information or real values showing how this can be done. It appears that I'll need to use some op-amps to do this, but does anyone have any practical cicuit (I.E. one that has values) that they can recommend/share?
Thank You,
Gordon





RE: Bipolar to Unipolar Voltage Conversion Help Needed
If the former then a precision rectifier would fit the bill, i.e. an absolute value circuit, with a gain of 2 to match the +1.5V F.S output of the precision rectifier to the 3V input span.
If the latter then a level shifter would let you scale, say, 0V = negative F.S, 1.5V = zero current, +3V = positve F.S.
So... which are you trying to do?
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If we learn from our mistakes I'm getting a great education!
RE: Bipolar to Unipolar Voltage Conversion Help Needed
I am trying to do a level shifter and your scale is exactly what I need (i.e. 0V = negative F.S, 1.5V = zero current, +3V = positve F.S.).
Gordon
RE: Bipolar to Unipolar Voltage Conversion Help Needed
You might want to invest in, or borrow, a copy of 'the Art of Electronics' by Horowitz & Hill. It's getting a bit long in the tooth in trms of the specific devices it uses but is very readable and full of good circuit ideas.
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If we learn from our mistakes I'm getting a great education!
RE: Bipolar to Unipolar Voltage Conversion Help Needed
Assuming the LEM(s) has a dedicated +/- 15 volt regulated supply simply use a voltage divider to give you -1.5V which can be connected to the micro-controller 0 reference.
I wonder what effect using an offset supply would have e.g. +15/-13.5.
The LA 100-P is an interesting transducer. It seems obvious to me that with the 3 wire connection shown, the supplies need to be regulated or at least go up and down together otherwise the output will suffer from zero offset.
If the micro-controller input impedance is high. A crude temporary fix would be to simply add a 1.5V cell into the circuit.
Regards
Roy