Rockwell Automation T8824 Trusted 40 Channel 120V ac Digital Input FTA - Manual (Page 7)

Trusted
TM
120Vac Digital Input FTA T8824
Issue 4 Sep 11 PD-T8824 7
2. Installation
Trusted TM 40 Channel 120Vac Digital Input FTA T8824 is designed to be mounted on either of the
TS32 or TS35 DIN rails in the horizontal or vertical positions as required.
3. Associated Cable Selection
Refer to the product descriptions detailed below:
PD-TC000 Trusted TM Power Cables
PD-TC200 Trusted TM I/O Companion Slot Cables
4. Cable Capacitance
With long field cables the capacitive coupling of the cable can cause a significant voltage to be seen at
the T8424 input when the field switch is open. This causes the T8424 to report that the field switch is
still on when it is turned off.
Revision E T8824 FTAs have lower loop resistance, which reduces the capacitive noise and increases
the available loop length.
The table below shows some estimated maximum lengths for different cables and mains supplies.
Practical distances will be less than this due to other noise and for switching safety margins.
Revision E Earlier revisions
15pF/m, 110V, 50Hz 2940m 890m
30pF/m, 110V, 50Hz 1470m 470m
15pF/m, 110V, 60Hz 2450m 790m
30pF/m, 110V, 60Hz 1220m 390m
15pF/m, 120V, 50Hz 2620m 850m
30pF/m, 120V, 50Hz 1310m 420m
15pF/m, 120V, 60Hz 2190m 700m
30pF/m, 120V, 60Hz 1090m 350m
Table 1 Theoretical maximum cable lengths