Is there an industry standard or performance expectation for 2 wire 4-20mA output devices (actuators, positioners) for signal levels below 4mA? For example, many field transmitters incorporate special signal indications outside the 4-20mA interval for alarm levels or diagnostic indications. And I am aware that for valve positioning driving sometimes DCS systems incorporate driving below 4mA (or above 20mA) to assure valve seating at the endpoints.
Thanks in advance for your comments and replies
Thanks in advance for your comments and replies