Manual 82510
Magnetic Pickups and Proximity Switches
Woodward
13
Types of Proximity Switches
Two different sizes of proximity switch are available from Woodward:
1. A proximity switch with a fairly narrow sensing field, suitable for medium size gears with a tooth size
from diametral pitch 8 to 12 (gear module 3 to 2). This switch can be mounted flush with the
mounting plate with an air gap up to 5.00 mm (0.197 inch).
2. A proximity switch with a wide sensing field is available for large gears where a wide air gap
(maximum of 10 mm / 0.4 inch) is necessary. This sensor requires larger gear sizes for proper
operation and should be used for gears larger than diametral pitch 12 (gear module 2.1). There must
be a 30 mm (1.1 inch) radius clearance of metal around the front of the sensor and mounting
bracket.
Some Woodward controls have less than 300
Ω
of dc impedance. In
these cases, the probe may be damaged by excess current when the
engine is stopped. To prevent this possible damage, a 300
Ω
, 2 W
resistor should be installed in series with the probe.
Proximity Switch Power Supply
Proximity switches provided by Woodward require an external power supply of a single dc voltage,
usually 24 volts. This may be from the same supply source as power for the control system. The
maximum current rating for these proximity switches is 80 mA, but actual current is less and dependent
on the external load.
The red plastic cap on top of the proximity switch is an integral part
of the device, not a loose shipping cover. The proximity switch can
be damaged beyond repair if an attempt is made to remove the cap.
Figure 2-1. Air Gaps for Radial and Axial Sensing Proximity Switches
Released
