201/203/205/207 Series Flowmeters and Controllers Instruction Manual
EAR99 Technology Subject to Restrictions Contained on the Cover Page
Page 9 of 28
Optional 4-20 mA Current Output
An option to the standard 0-5 VDC output is the 4-20 mA current output that is proportional to flow. The 4-20
mA signal is produced from the 0-5 VDC output of the flow meter. The current loop output is useful for remote
applications where pickup noise could substantially affect the stability of the voltage output or long cable runs
where cable resistance would cause a voltage signal to decay.
The current loop signal replaces the voltage output on pin 6 of the DA-15 connector (pin 2 of DE-9 24 Volt).
The current loop is sourced internally from the +15 VDC supply and must be returned to the signal supply
common after (pin 5 [±15 VDC] or pin 8 [24 VDC]) passing through the monitoring circuitry to complete the
loop. The load must be between 0 and 600 Ohm.
The 4-20 mA I/O option can accept a current input for flow controllers. The 0-5 VDC command signal on pin 14
(pin 3 for 24 Volts) can be replaced by a 4
–
20 mA command signal. The loop presents an impedance of 50
Ohms and is returned to the signal common. On the 24 Volt units, the signal common will need to be tied to
the power supply common external to the flow controller to complete the loop since the signal common is
galvanically isolated internally from the supply common. This line must be current limited (< 50 mA) to
prevent short circuit currents from damaging the receiving circuit in the flow controller.