Rockwell Automation T8846 Trusted Speed Monitor IFTA (SIFTA) - Manual (Page 18)

Trusted
TM
Speed Monitor IFTA T8846
Issue 2 Apr 10 PD-T8846 18
4. Field Connection Arrangements
This section shows the speed input connection arrangements for typical sensor configurations.
Active sensors are considered as field powered devices, and are available in two principal varieties:
• Totem Pole output sensors, actively drive their outputs to a positive potential and to ground
and do not rely on an external voltage bias.
• Open Collector output sensors, can only actively drive their outputs to ground and rely on an
external pull-up resistor to bias the output to a positive potential. The T8846 SIFTA provides
the biasing components for this type of sensor.
Passive sensors are considered to be magnetic, inductive pick up devices with no field power
requirements.
4.1. Active Totem Pole Output Sensor Types
4.1.1. Sensor Power Derived from FTA
Figure 4 shows a typical field connection scheme for +24Vdc field powered speed sensors with totem
pole outputs. This arrangement uses the fused field supply derived from the FTA.
Figure 4 Active Totem Pole Output Sensor Connections (FTA Derived Field Supply)