Mettler Toledo IND780 Guide D'installation page 76

2.7.7.2.2. Passive Input
Selecting the inputs as passive enables other devices such as PLCs to provide the trigger voltage
(typically 24 VDC, 5-30 VDC) to turn the IND780 inputs "on". An example of wiring to the passive
inputs is shown in Figure 2-80. The voltage polarity may be reversed. Furthermore, inputs can be
programmed in SETUP to accept either a + True or – True polarity level as "ON".
Note – The voltage source
must be a Class 2
marked or a Limited
Power Source (LPS)-
compliant power supply
2-52
METTLER TOLEDO IND780 Installation Guide
The +5VDC shown in Figure 2-79 is referenced to an internal ground inside the discrete I/O
card. Measuring from pin 10 to the IND780 chassis ground will not show +5VDC. The
+5VDC output is used internally, and has no function except for digital inputs as shown in
Figure 2-79.
Figure 2-80: Example of Passive Input from Discrete Output Device
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