Manual 26710V1
ProTechTPS Total Protection System
Woodward
41
Configurable Discrete and Analog Inputs—
Discrete Input Wiring
When an input is configured to function as a discrete input, it must be wired as
shown in Figures 2-13a or 2-13b to function properly. Contact wetting voltage is
available through terminal 37
.
Discrete input wires do not need to be shielded,
but may be shielded. If shielding is used, terminate shield as indicated on AI
mode. If a shield is used, a common wire must be run with the signal wire for field
powered DI’s, and both power & common must run with the signal wire for
ProTechTPS powered DI’s. Shielded DI’s may be grouped with multiple signals &
one common/power wire in a single shield. In general, an input contact signal
must change state for a minimum of 8 milliseconds for a ProTechTPS module to
sense and register a change in state. Refer to Chapter 3 (Functionality) of this
manual for information on how to program and use each discrete input in an
application.
If total current draw through terminal 37 exceeds 50 mA, the power
supply’s internal breaker will open. Upon such a condition, all load
must be removed from the specified terminals to allow this breaker
to reset. The internal 24 V provides enough power to operate all 10
inputs in discrete mode.
For reliability reasons, Woodward recommends that input circuitry
for each module (A, B, C) be fully isolated from the input circuitry of
the other two modules. For example, the power source and wiring for
module A should not be shared or connected in any way to modules
B or C.
If desired, an external 18–26 Vdc power source can be used for the
circuit-wetting voltage. In this case, terminal 38 (contact input
common) must be connected to the external power source’s
common to establish a common reference point. Each contact input
pulls 4.8 mA at 24 V when closed and requires at least 2.5 mA and 14
V to recognize a closure command. Refer to Figure 2-13b for wiring
information.
Woodward recommends that separate input transducers be utilized
for each ProTechTPS module (A, B, C) to reduce nuisance trips,
increase system availability, and simplify unit replacement.
Figure 2-13a. Example Configurable Input Wiring—Discrete Input (Internal Power
Option)
