Understanding Wiring Diagrams
II-C. Connection of Actuators
0 to 10 V Control Signals
Signal Loss
Due to the high input impedance (100k
Ω
) of the actuators, the current through the signal wire is very low.
Therefore, the loss of signal will be negligible, even if with long wire runs.
Example: Three actuators are connected via a 330 ft. (100 meters) long pair of 22 Ga. wires. Each wire has a
resistance of 5
Ω
.
The current draw from each actuator is (I = E/R) 10/100,000 = 0.1 mA, when the signal is 10 VDC.
The current in the wire will be 3 x 0.1 = 0.3 mA. Because 2 wires, the Common and the Source, go to the actuator,
the resistance in the wires is 2 x 5
Ω
= 10
Ω
. The loss of signal will be (E = R x I) 10 x 0.3 = 3 mV = -.003V.
4 to 20 mA Control Signals
The controller will regulate the output current (signal) to the desired value, regardless of the resistance (up to a specified value) in
the wires and the load resistor.
The resistance in the wires will only cause the output voltage of the controller to be slightly higher than the input of the actuators.
The advantage with a 4 to 20 mA output signal to the actuators is that wire resistance does not cause any error to the control signal,
and that electrical interference is rejected.
The input impedance of the actuators will reduce the resulting resistance of the load resistor. However, the error is so small that
there is no need to compensate for this by using a slightly higher resistance value. A 500
Ω
load resistor will give an adequate accu-
racy. Use a 499
Ω
, 1%, 1/2w resistor or two 1k
Ω
, 1%, 1/4 w resistors in parallel.
TRANSFORMER
CONTROLLER
Analog Output Board
4 to 20mA
LOAD
RESISTOR
4 to 20mA
3
2
1
3
2
1
3
2
1
(+)
(–)
(+)
(–)
500
COM
⊥
24 V
A
C
HOT
~
L
I
N
E
L I N E
ALWAYS USE A SEPARATE
TRANSFORMER FOR THE
CONTROLLER UNLESS YOU
KNOW A HALF-WAVE
RECTIFIER IS USED!
ACTUATOR* ACTUATOR*
ACTUATOR*
TRANSFORMER
ALWAYS USE A SEPARATE
TRANSFORMER FOR THE
CONTROLLER UNLESS YOU
KNOW A HALF-WAVE
RECTIFIER IS USED!
CONTROLLER
Analog Output Board
0 to 10V
I = .3 mA
330 ft., 22 Ga.
(+)
(–)
(+)
(–)
COM
⊥
24 V
A
C
HOT
~
3
2
1
3
2
1
3
2
1
ACTUATOR
L
I
N
E
L I N E
10 V
10.0 - .003 = 9.997 V
ACTUATOR
ACTUATOR
* up to 4 actuators may be
wired to one load resistor
without a significant
range shift.
150
I20683 - Subject to change.
Summary of Contents for TRANE TAF Series
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