Hi Experts,
Good day.
We would like to ask your assistance in looking for high reliable parts for this current to conversation.
Client need to measure the pressure using our op-amp with a pressure sensor (2 wire), working voltage 24v dc and signal is 4 to 20mA.
Can you suggest an op-amp part and a ref design (if possible) also?
Thank you.
Hi Archie,
Perhaps a review of the HiRel Product listing of Amplifiers would be useful:
https://www.ti.com/applications/industrial/aerospace-defense/products.html
,
There are several Current Sense amplifiers list, such as
Leonard, Artzy,
As intuitive as it seems given the 24V common mode here, current sense amplifiers are typically not used in 4-20mA applications because of the size of the shunt resistors typically utilized for these systems against the increased nature of the input bias currents seen across them.
For the INA193-EP or INA271-HT, the minimum sense voltage generated must be kept above 20mV for normal operation, and the linear operating region is 20mV to 100mV, meaning the most accurate information will be obtained there. Basing the application on a 5Ω shunt which would map the input range exactly to the linear operating range, this is what the error curve would look like:
Before taking any other error into consideration, just from the device itself, the error when measuring 4mA would be 19.53%, down to 4.03% at 20mA for the INA193-EP. The error for the INA271-HT is off the chart.
It looks like we've looped the precision amplifier group into the conversation. I would see if they can recommend a part here that might perform a bit better in the application. Does the customer have access to supplies that would cover the input common mode range of a standard op amp here?
