ENCODER INTEGRITY
Steering and height encoders are tested continu-
ously for current draw. If the total current draw
from the two encoders and the Hall effect sensor is
too high or too low, a fault will be generated and
truck operation will be inhibited. Additional soft-
ware continuously checks the output bit sequence
activity of the steering input encoder to ensure that
both bits are operating.
TEST ENCODERS
NOTE:
This procedure applies to the height en-
coder and the AC motor speed encoders. The height
encoder operates from a 5 volt supply and the AC
motor speed encoders operate from a 12 volt supply.
Conventional means can be used to diagnose the
encoders as follows. Using a voltmeter, determine if
5 or 12 volts and battery negative are going to each
encoder by back-probing the connector. If good,
then connect to one output channel and battery
negative, and rotate the encoder very slowly to see
if the input channel goes on/off/on (0 then 5 volts
from the height encoder) when the encoder is rota-
ted slowly. Check the other output channel as well.
If they are both outputting the proper LED signal
or voltage then the encoder is OK. See Setup.
PROXIMITY SWITCHES
These are noncontact devices which sense the pres-
ence of steel. They have three wires going to them:
battery negative, supply voltage, and an output sig-
nal. See Table 1 and Figure 52. They also have a
built-in indicator light that lights the collar where
the wires enter the proximity switch. These devices
can be checked by looking at the indicator light and
by testing the output with a voltmeter to see that it
changes with and without the steel in front of it.
Proximity switches may also be used to perform
signal inputs for speed reduction mast cushion re-
set and battery interlock functions.
Table 1. Proximity Switches
Device
Supply
Output Voltage
(Sensing Metal)
Indicator Light
PNP or NPN
Mast Proximity
Constant B(-) supplied Sources battery voltage
to Lift Pump Controller
ON
PNP Sourcing
Reach Proximity
Ground supplied by
EXT/RET Coil when
energized
Sources battery voltage
to CAN I/O
ON
PNP Sourcing
Height Proximity
Constant B(-) supplied Sources battery voltage
to Remote CAN (If
equipped)
ON
PNP Sourcing
MDU Proximity
B(+)
Main Steer Controller
ground signal provided
to Main Steer Controller
input
ON
NPN Sinking
Caster Proximity
B(+)
Caster Controller
ground signal provided
to Caster Controller
input
ON
NPN Sinking
2200 SRM 1612
Major Electrical System Features
9
