Current Loop Transmitter Impedance; Wiring Diagram - 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 F4-04AD provides 250 ohm resistance for each channel. If your transmitter
requires a load resistance below 250 ohms, you do not have to make any
adjustments. However, if your transmitter requires a load resistance higher than
250 ohms, 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 minimum load resistance of 750 ohms. Since the
module has a 250 ohm resistor, you need to add an additional resistor.
See Errata Sheet at the
beginning of this file. This
example drawing was
revised. The power
supply 0V terminal, and
the Channel 1 Common
and 0V terminals were
connected.
The F4-04AD module has a removable connector to make wiring easier. Simply

Wiring Diagram

remove the retaining screws and gently pull the connector from the module.
NOTE 1: Shields should be grounded at the signal source.
NOTE 2: Unused channels should be shorted for best noise immunity.
NOTE 3: When a differential input is not used, 0V should be connected to C of the channel.
See NOTE 1
CH1
+
Single-ended Voltage
–
Transmitter
CH2
Differential Voltage
Transmitter
CH3
Differential Current
Transmitter
CH4
Not Used
See NOTE 2
User Supply 21.6 – 26.4 VDC
R = Tr – Mr
R = 750 – 250
R  500
DC Supply
+36V
0V
See
NOTE 3
+
OV
–
+
OV
–
+ –
Class 2
F4–04AD 4 Channel Analog Input
R – resistor to add
Tr – Transmitter Requirement
Mr – Module resistance (internal 250 ohms)
Two-wire Transmitter
+ –
Internal
Module
V
Wiring
C
(front end)
I
OV
250 ohms
V
C
I
+
OV
–
250 ohms
V
C
OV
I
OV
250 ohms
V
C
I
OV
250 ohms
User
Supply
Return
Channel select
OV
Module Channel 1
V
R
C
I
0V
250 ohms
ANALOG INPUT
TB 24V RUN NEG
DATA
1 16 256 CH1
2 32 512 CH2
4 64 1024 CH3
8 128 2048 CH4
F4–04AD
DISPLAY
CH
V
A to D
C
Convertor
CH1
I
OV
V
C
CH2 I
OV
V
C
CH3
I
OV
V
C
CH4
I
OV
0–10VDC
1–5VDC
–10–+10VDC
4mA–20mA
24VDC 0.1A
CLASS 2
F4–04AD
3–11