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20 Point Multiplex Modules—Multiplex Binary
Unpowered Triac or SCR
If the XBN input is coming from a transmitter device with a triac or SCR
output, an AC source must power the output. If the transmitter does not
supply the AC power to the output, you must add the power externally.
Connect the AC voltage through a limiting resistor, as shown in Figure 15.
The following equation calculates the resistor to be used:
The holding current is listed in the triac or SCR rating.
Determine the wattage of the added resistor by either of these two
equations (power is doubled in the equations to accommodate safety
standards):
where I is the load current, E is the source voltage (e.g., 120 VAC), and
R is the resistor.
Set the XBN switch to Voltage mode.
To create a voltage bias, add the power line and
resistor shown in the shaded area.
Add Resistor
120 V
Figure 15: Adding a Voltage Bias Circuit to an Unpowered Triac or
Voltage
Supply
Resistor =
Current
Holding
P = 2I
R
P =
or
2
Transmitter With
Triac Output
(e.g., power monitoring
transmitter or rate/flow
transmitter)
SCR Device
- 1.6
2E
2
R
xbn13
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