Rockwell Automation Publication 440R-UM013G-EN-P - December 2022 59
Chapter 11 Troubleshooting
b. If only one input is above the turn on voltage level, then the IN status 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 63 - 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 67 on page 61). S11 is
effectively off longer than S21.
1. Check the safety inputs with the device contacts open, as shown in Figure 64
.
Figure 64 - Typical Voltage Measurements of the DI, DIS, and SI Safety Relays with Contacts Open
2. Check the voltage at each of the inputs with the device contacts closed. The values
must be very close to the values measured at terminals S11 and S21.
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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