4-20mA input with programmable offset and gain.

155

01:47:32

This is a circuit for a 4-20mA input. There is a subtracting offset stage followed by a gain stage. I want to replace the pots by digital pots to make it programmable. The comparator up top is open circuit detector which will be connected to the MCU. The op-amps are single supply. The reference voltage of ADC will be 2.5V. Any comments on improvements?

published 11 years ago

UncleRick

11 years ago

I'm not quite sure what you mean by "digital pots". However... The op-amps have dual 15 volt supplies. (They are hidden & assumed to be there.) You can however limit them to one supply or the other by how you configure their inputs. Perhaps you mean "digital rotary 10 step switches" in which you can have your choice of resistors connected for each step of gain. Other than that you may need rotary encoders with digital decoders to set solid state relays, to select the resistors. There are likely more digital possibilities for programming the op-amp gain.

ianperkins

11 years ago

@UncleRick : there are digital pots, i for one own some. https://www.sparkfun.com/products/10613

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