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5. PRINCIPLES OF WORK
5.1. The LRB 20000 assembly (Fig.1) consists of rangefinder 1
mounted on the angular mount 2. The latter is mounted on the
tripod 3.
5.2. Rangefinder (Fig.2) is designed for terrain observation and
measuring the distance to the closest or next-in range target
caught in the beam. It works with the principle of measuring the
light pulse round-trip time. The measurement result is displayed
in meters on digital range indicator and can be also stored in the
computer for further calculations.
The schematic circuit diagram of range finder (Fig.3) shows
rechargeable battery (G1), controls switches (S1- S4), pumping
and firing elements (ref. designations C1-C3, E1, L1, T1, V1-
V2), control circuit board (A1), display circuit board (A2),
counter circuit board (A3), and photodetector assembly (A4).
Toggle switch S1 is operated to energize the range finder, and
toggle switch S4 – to light up the light-emitting diode (LED) H1
which illuminates the reticle pattern.
Button switches S2 and S3 labeled (MEASURE 1) and
(MEASURE L) respectively are used to prepare the rangefinder
for taking a measurement (by pressing one of those buttons).
Button S2 is operated to range the closest target, whereas
button S3 is used to engage the next-in-range target caught in the
beam.
11.2. The possible problems with the rangefinder are listed
below in Table 11.1
Table 11.1
Problem
description
Probable reason Solution
1. Picture is blurred
in the right-hand
eyepiece
2. Readiness
indicator remains
dark after
MEASURE 1
(MEASURE L)
button release
3. Red Low Battery
indicator is on
Condensed moisture,
dirt on external
optical surfaces
Condensed moisture
on internal optical
surfaces
Open circuit in the
battery section (when
standard battery is
used)
Blown fuse in the
protection device
(when vehicle
electrical system is
used)
Open circuit in
battery section (when
vehicle electrical
system is used)
Unallowably low
battery voltage
Clean exterior of optical
parts as directed under
10.6.2
Dry rangefinder as
directed under 10.6.3
Clean contacts as
directed under 10.6.1
Replace fuse as directed
under 11.3.1
Clean contacts as
directed under 10.6.1
Replace the battery with
a newly charged one as
directed under 11.3.2