Advertisement
Velocity Measurement
A velocity is measured by observing the change in distance over a fixed time period. The default time period
is 100 ms resulting in a velocity calibration of .1 m/s. Velocity mode is selected by setting the most
significant bit of internal register 4 to one. When a distance measurement is initiated by writing a 3 or 4 (no
dc compensation/or update compensation respectively) to command register 0, two successive distance
measurements result with a time delay defined by the value loaded into register at address 0x68.
Measurement Period (ms) Velocity Scaling (meters/sec)
100
40
20
10
Velocity is output as an 8bit Two's Complement signed value read out from register [0x09]. Velocity is the
difference between the last two 16bit distance measurements. The previous distance measurement used in
the velocity calculation is available from registers [0x14] and [0x15] with [14] containing the most significant
byte and [15] the least.
To measure velocity with measurement period less than 20 ms, adjustment of the acquisition parameters will
likely be necessary. The nominal acquisition is between 1015 ms allowing insufficient time to complete the
first velocity acquisition period before starting the second.
Measurement acquisition times can be reduced by the elimination of the reference pulse acquisition and
performing the acquisition without a prior DC compensation step. The setting of bit position 6 (adjacent to
the velocity mode selection bit) in register [4] suppresses the acquisition of the reference pulse and the
loading of 3 into the command register 0 performs an acquisition without the normal DC compensation step.
The DC compensation needs to be performed every few seconds when the sensor is first warming up, but
once thermally stable compensation can occur at a much slower rate.
LIDARLite v1 "Silver Label" Manual , Updated: 08/13/15
.1 m/s
.25 m/s
.5 m/s
1 m/s
Register (0x68) Load
Value
0xC8
0x50
0x28
0x14
Advertisement
