Rockwell Automation Publication 440R-UM010A-EN-P - May 2015
31
Chapter
6
Pulse Testing Functions
Pulse Testing For Inputs
Pulse testing for the inputs is always active. The pulses are generated at terminals
S11 and S21. These test pulses should be used with devices that have mechanical
contacts.
S11 is typically connected to one contact and the other side of the contact is
connected to S12. S21 is typically connected to the second contact, and the other
side of the second contact is connected to S22.
The test pulses are used by the GLT to detect three short circuit conditions:
1.
Between the input terminals and +24V
2.
Between the input terminals and 24V common
3.
Between the two input terminals
shows the timings of the two test pulses. The pulse on S21 occurs
shortly after S11. The pulses are repeated every 15 ms.
Figure 22 - Pulse Test Signals
Pulse Testing of Outputs
When the GLT configuration process starts from Logic Switch setting 0, the 14,
24, 51, and L61 outputs are pulse tested. The purpose of the pulse testing is to
detect short circuits to 24V, to 24V common, and short circuits between the
output terminals. The use of pulse testing allows the GLT to be used in PLe and
SIL3 applications. Without pulse testing, the GLT can only be used in
applications up to PLd and SIL2.
The outputs have built in redundancy. A main transistor supplies power to
individual transistors for each output terminal as shown in
Figure 23 - Output Transistor Arrangement
Terminal S21
Terminal S11
24V
15 ms
575 to 775µs
350 µs
0
0V
24V
0V
Main Transistor
Individual Transistors
24
14
L61
51
