Hello everyone!,
I have a pressure transducer that I need to interface with a 0-3.3V ADC. The output of the sensor is the typical 4-20mA.
I have seen Maxim's appnote http://pdfserv.maxim-ic.com/en/an/AN823.pdf , which converts 4-20mA to 0-5V. This is done by a current shunt, with an appropriate gain, then a subtraction for the 4mA offset via a reference. This is a 'high-side' scheme, which requires the opamps common-mode input voltage to be high, thus necessitating high common-mode rejection.
My question is, why not use low-side current sensing? You can use much better opamps (lower offset, offset tempco, noise, cmrr, etc.). Is there some industrial reason for this?, like detecting faults or something?
I want to get as much precision as possible with the circuit, since it is a one-off prototype and money isn't too much of an issue.
Thanks!
Steve
I have a pressure transducer that I need to interface with a 0-3.3V ADC. The output of the sensor is the typical 4-20mA.
I have seen Maxim's appnote http://pdfserv.maxim-ic.com/en/an/AN823.pdf , which converts 4-20mA to 0-5V. This is done by a current shunt, with an appropriate gain, then a subtraction for the 4mA offset via a reference. This is a 'high-side' scheme, which requires the opamps common-mode input voltage to be high, thus necessitating high common-mode rejection.
My question is, why not use low-side current sensing? You can use much better opamps (lower offset, offset tempco, noise, cmrr, etc.). Is there some industrial reason for this?, like detecting faults or something?
I want to get as much precision as possible with the circuit, since it is a one-off prototype and money isn't too much of an issue.
Thanks!
Steve