GLX-RSS-2-300 WL User Manual
37
GLX-RSS-2-300 WL Non-Contact Flow Meter
The command that puts the instrument to
Power save mode
is as follows:
<0x2b> ID CSUM:
0x2b:
The first byte sent in the request is ‘+‘ character. Its ASCII value in HEX is
0x2b.
ID:
Exactly two bytes long. This is the unit ID written as two ASCII characters.
For example, if the polled unit ID is 2, then ID will be sent as “02”. In HEX
representation it is the following two bytes: <0x30><0x32>.
CSUM:
Checksum, calculated by adding in modulo 256 the two byte values of the
ID. If the device ID is 2, then ID was sent as <0x30><0x32>. Checksum is
then 0x30+0x32 = <0x62>.
After receiving the request, the device goes to power save mode.
The command that restores the instrument from
Power save mode
to normal
Operational mode
is as
follows:
<0x2d> ID CSUM
0x2d:
The first byte sent in the request is ‘-‘ character. Its ASCII value in HEX is
0x2d.
ID:
Exactly two bytes long. This is the unit ID written as two ASCII characters.
For example, if the polled unit ID is 2, then ID will be sent as “02”. In HEX
representation it is the following two bytes: <0x30><0x32>.
CSUM:
Checksum, calculated by adding in modulo 256 the two byte values of the
ID. If the device ID is 2, then ID was sent as <0x30><0x32>. Checksum is
then 0x30+0x32 = <0x62>
After receiving the request, the device goes from
Power save mode
to normal
Operational mode
.
7.5. Modbus Protocol (RS-485)
When configured in Modbus operation mode, the unit responds to Modbus requests over RS-485 data
line. The baud rate and device ID configured through the PC application, and 1 stop bit, even parity, 8
data bits configuration is used.
Modbus registers that are accessed by Modbus protocol are 16-bit (2-byte) registers. Any number of
registers can be read or written to over Modbus.
Modbus is a request-response protocol where a master (such as datalogger) sends out requests, and
slave devices (such as RSS-2-300 WL sensor) respond. The request and response format, with exam
-
ples is given in tables 3-6.
In each request, the master can either ask the slave to retrieve the value of one or more registers, or the
master can set the value of one or more registers. Each register holds one 16-bit value.