Rockwell Automation Publication 440R-UM013F-EN-P - July 2021 59
Chapter 11 Troubleshooting
a. If both channels are closed, a voltmeter must read about 19V and the
IN indicator is green. The voltage levels are approximately the same on
Channel 1 (S12) and Channel 2 (S22) because the pulse testing
waveforms are similar on both channels.
b. If only one input is above the turn ON voltage level, then the IN
indicator is red.
c. Try cycling the input device.
d. If the contacts of the safety device do not operate consistently, the
safety device must be replaced.
Figure 61 - Check the CI Safety Inputs with the Device Contacts Closed
3. If a significant difference in voltage levels exists, see Capacitance Effect
on page 61 and Long Wire — Resistance Effect on page 62.
To find where the voltage drop is occurring, you have to trace the wiring
of the circuit that is not achieving at least 11V as measured by an
oscilloscope.
Check DI, DIS, and SI Safety Relays
DI, DIS, and SI safety relays can also be checked in a similar fashion. The
voltage of Channel 1 is lower (about 14V) than Channel 2 (about 18V). The
reason for the difference in voltage levels is due to the difference in the pulse
test wave forms (see Figure 65 on page 61
). S11 is effectively OFF longer
than S21.
1. Check the safety inputs with the device contacts open, as shown in
Figure 62
.
Figure 62 - Typical Voltage Measurements of the DI, DIS, and SI Safety Relays with Contacts Open
The SI safety relay does not have terminals S32 and S42.
S11 S21S12
19
19
S22
A2
Volts
DMM
Volts
DMM
Volts
DMM
Volts
DMM
S11 S21 S12 S22 S32 S42
14
18
A2
Pulse
Test ing
Outputs
Device 1 Device 2
Input 1 Input 2
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