Current Loop Transmitter Impedance; Removable Connector - Automation Direct DL405 User Manual

Current Loop Standard 4 to 20 mA transmitters and transducers can operate from a wide variety
Transmitter of power supplies. Not all transmitters are alike and the manufacturers often specify
Impedance a minimum loop or load resistance that must be used with the transmitter.
The F4-08AD provides 250 ohm resistance for each channel. If your transmitter
requires a load resistance below 250 ohms, then you do not have to make any
adjustments. However, if your transmitter requires a load resistance higher than
250 ohms, then you need to add a resistor in series with the module.
Consider the following example for a transmitter being operated from a 36 VDC
supply with a recommended load resistance of 750 ohms. Since the module has a
250 ohm resistor, you need to add an additional resistor.
Removable The F4–08AD module has a removable connector to make wiring easier. Simply
Connector remove the retaining screws and gently pull the connector from the module.
R + Tr * Mr
R – resistor to add
R + 750 * 250
Tr – Transmitter Requirement
R w 500
Mr – Module resistance (internal 250 ohms)
DC Supply
0V
+36V
F4–08AD 8-Channel Analog Input
+ –
Two-wire Transmitter
Module Channel 1
–
250
R
ohms
+
5–7