User guide

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3.7: 952 VP (Variable Pulse)
The variable pulse signal interface of the BlueOx
digital output series is a pulse width modulated
signal (RS-422). The maximum cable length for the
differential LDTs is 1,500 feet. This LDT can also
be congured for external or internal interrogation.
External interrogation is when an external device
connected to the LDT generates a start pulse. This
start pulse should be a minimum of 1.0 microsecond
in duration. Within 50 nanoseconds after the leading
edge of the start pulse has been received, the LDT
will generate an output pulse. The duration of the
Figure 3-4: 952VP with External Interrogation
INPUT (INTERROGATION)
1 MICROSECOND (RECOMMENDED)
0.2 MICROSECONDS (MINIMUM)
WIDTH OF PULSE IS PROPORTIONAL TO
DISTANCE BETWEEN MAGNET AND HEX HEAD
OUTPUT PULSE
WITHIN 50 NANOSECONDS AFTER INTERROGATION
TO DISTANCE BETWEEN MAGNET AND HEX HEAD
OUTPUT PULSE
LOW OUTPUT VARIES DEPENDING ON LENGTH
PROGRAMMED VIA DIP SW2 SWITCHES 1-6
WIDTH OF PULSE IS PROPORTIONAL
TO DISTANCE BETWEEN MAGNET AND HEX HEAD
output pulse is proportional to the distance from
the magnet to the hex head. The order of these two
pulses is illustrated in Figure 3-4. The 952VP can
also generate internal interrogations. This LDT will
continually output pulse width modulated signals.
As with a 952VP using an external interrogation,
the duration of this output pulse is proportional to
the distance from the magnet to the hex head. This
is illustrated in Figure 3-5. To wire the 952VP, see
Figure 3-7. For proper grounding information, see
the beginning of this chapter.
Figure 3-5: 952VP with Internal Interrogation