60 Rockwell Automation Publication 440R-UM013F-EN-P - July 2021
Chapter 11 Troubleshooting
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.
Figure 63 - Typical Voltage Measurements of the DI, DIS, and SI Safety Relays with 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.
Examine Pulse Test Waveforms
If you have an oscilloscope, you can examine the pulse tests. The test pulses are
used to check for short-circuit conditions; the test pulses are not used to turn
the inputs ON and OFF. If they are clean and square, then they are OK.
The test pulses are generated on terminals S11 and S21. The waveforms, which
are shown in Figure 64
and Figure 65 on page 61, must always be present on
their respective relays; the test pulses cannot be turned off or adjusted.
Figure 64 - CI Safety Relay Pulse Test Waveforms
Volts
DMM
Volts
DMM
S11 S21 S12 S22 S32 S42
14
18
A2
Pulse
Testing
Outputs
Device 1 Device 2
Input 1 Input 2
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