Campbell Scientific SR50A Distance Sensor - Manual (Page 22)

SR50A Sonic Ranging Sensor
BBBBB
This is the checksum of the boot code.
WWWWW
This is the checksum of the firmware.
CC
This is a 2 character checksum of the data packet. The checksum is the two’s
complement of the data packet sum including control characters.
The least significant byte is used resulting in a 2 character checksum.
<STX> = &h02 (Hexadecimal)
<CR> = &h0D (Hexadecimal)
<LF> = &h0A (Hexadecimal)
<ETX> = &h03 (Hexadecimal)
The following is a sample packet with proper checksum:
<STX>33;1838;194;11011;2C<CR><LF><ETX>
SUM
=
02+33+33+3B+31+38+33+38+3B+31+39+34+3B+31+31+30+31+31
+3B+0D+0A+03
=0x3D4
Use Last byte only (D4) and calculate two’s complement = 100 – D4 = 2C
<CR>
Carriage return character. &h0D in hexadecimal or 13 in decimal
<LF>
Line feed character. &h0A in hexadecimal or 10 in decimal
<ETX>
End of transmission character. &h03 in hexadecimal or 3 in decimal
4. Sensor Mounting and Installation
4.1 Beam Angle
When mounting the SR50A, the sensor's beam angle needs to be considered
(see FIGURE 2. Beam Angle Clearance). It is always best to mount the
SR50A perpendicular to the intended target surface. The SR50A has a beam
angle of approximately 30 degrees. This means that objects outside this 30
degree beam will not be detected nor interfere with the intended target. Any
unwanted target must be outside the 30 degree beam angle.
The following formula is used to determine the required clearance for the beam
angle. By inserting a height value in the Formula, a Clearance Radius in the
same measurement units as the height can be obtained.
Clearance Radius formula:
( )
CONE 0. = CONE
height radius
268
FORMULA 2. Beam angle clearance Radius
16