User Manual

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© AGD Systems Ltd 2010. All rights reserved., the information contained in this document is the property of AGD Systems Ltd., and is supplied
without liability for errors or omissions. AGD315 User Manual Page 10 of 12
7.4 Maximum Speed Measurement
Normally, the radar can detect targets travelling in both directions simultaneously (if required) at
speeds of up to 128mph. The radar can resolve the speed to the nearest Doppler bin, which is
approximately equal to 1mph.
In some situations, it may be required that the radar measure higher target speeds than 128mph. It is
possible to configure the radar to measure targets up to 255mph, but with the caveat that the radar
must be set into either advance or recede mode (not bidirectional), and targets travelling in the wrong
direction at sufficient speed will generate erroneous speed readings which appear to have come from
the required direction.
For example, if the radar is set into advance mode, and the command *RV<space>150<cr> is sent
to the radar, the following behaviour will be seen:
Vehicle
Speed (mph)
Vehicle
Direction
Radar Operation
0 – 10
Approach
Vehicle not detected, speed is below the low speed cutoff
10 – 150
Approach
Vehicle detected, speed and direction measured correctly, message sent
150+
Approach
Vehicle not detected, speed is above upper limit set by *RV
0 – 10
Recede
Vehicle not detected, speed is below the low speed cutoff
10-105
Recede
Vehicle detected, speed and direction measured correctly, no message
105+
Recede
Vehicle detected, speed and direction measured incorrectly, message sent
Table 3 Maximum Speed Behaviour
So, the *RV command is used to set the maximum speed measurable in the required direction. Under
most situations, the erroneous speed measured can be filtered out because the range measurement
will be incorrect.
One situation where the range cannot be used to filter out erroneous targets is for a vehicle driving the
wrong way down the road at excessive speed (for example, a vehicle driving the wrong way down a
dual carriageway or motorway). However, two radars deployed at the same position, one set to
approach and one set to recede, both with the same *RV setting could be used under these
circumstances, which would give the capability to measure up to ±255mph (255mmph approach with
one radar, 255mph recede with the other). Under most normal situations however, a single radar will
the capability for ±128mph should be sufficient.