| The Type
858 Optical detector is used to generate an output pulse when a
projectile passes immediately overhead. It can be used in
conjunction with other units such as the 817 to provide a
Projectile Velocity Measuring System. Such a system can, to
within an accuracy of 0.1%, record velocities from as low as 10
metres per second to in excess of 5000 metres per second. Under
normal conditions, the projectile would be detected at a height
of up to 500 times the projectile calibre.
The 858 is based on the previous
758 unit, but has been completely re-designed. The new unit is
now much more sensitive with blue light illumination and is
usable in nearly all outdoor lighting conditions. This rugged
and sophisticated system will operate where background
illumination conditions are as low as 50 foot- lamberts thereby
enabling it to be used successfully on both naturally lit
outdoor ranges, as well as artificially illuminated tunnel
ranges. Solid -State DC light sources Type 788 are available for
tunnel work. |
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| The
complete system requires a Velocity Computer and there are a
range of units available: The Velocity and Rate of Fire
interface unit type 813 and the Triple Channel Remote Timer
Unit type 817.All units permit rapid fire recordings of up to 256 shots.
The 813 and 817 are connected to a PC to
allow central data storage and printout. |
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| The
Optical Detectors are mounted on light alloy plinths from which
they can be easily removed. This feature allows the plinths to
be permanently installed on a range if required. The Detectors
may also be mounted on the tunnel wall which allows untidy floor
cable runs and obstructions to be avoided. A BNC Connector
mounted on the base of the Optical detector provides an analogue
voltage signal for projectile profile recording. Measurement of
the DC voltage level allows the DC Light to be easily aligned
with the Detector. |
As a
projectile passes through the field of view of the Start and
Stop Optical detectors, a small change in illumination is
detected. The electronic signal generated by each Detector is
processed and then transmitted to the Remote Control Unit which
can be situated up to 1 km away by using the Remote Junction
Box.
Incorporated within each Optical detector is an automatic gain
control system which compensates for ambient light changes. Also
incorporated is a special half way down trigger circuit to
ensure accurate triggering in base mode. The Remote Control Unit
not only converts the signals from the Detectors into Start and
Stop pulses suitable for triggering the Velocity Computer, but
also provides power for the whole system, and incorporates
controls as defined in the Specification overleaf.
An Indicator lamp is provided for each Detector which
momentarily extinguishes when a projectile is detected. Also
included is a 'Self Test' facility which enables the operator to
check the functioning of the system prior to firing.
A tracer shield can easily be fitted to the Optical detectors to
enable velocity measurement on tracer rounds to be made. Nose
mode should be selected when recording the velocity of tracer
rounds. |
A Test
set Type 761 is available which functionally checks the Optical
detectors.
A full calibration service traceable to national Standards is
also available. |
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