GLX-RSS-2-300 WL User Manual
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GLX-RSS-2-300 WL Non-Contact Flow Meter
7.3. Request-Response Protocol (RS-485)
A different data protocol is used on RS-485 interface which allows connection of multiple units on the
single RS-485 line. Before the units are connected on the single RS-485 bus, each unit must be config
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ured with a different device identifier. The device identifier is configured using the PC application. Please
check chapter 8 for instructions.
The request-response protocol, unlike NMEA protocol, does not automatically report periodic flow mea
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surement readings. Instead, when the unit is polled form the data logger, it responds with the measure
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ment.
7.4. HS Protocol
The request is sent from the data logger to the flow meter:
<0x25> ID CSUM
0x25:
The first byte sent in the request is ‘%’ character. Its ASCII value in HEX is
0x25.
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, if the device ID matches, the flow meter will respond with the current
averaged flow velocity reading:
<0xA5> ID SPEED;LEVEL CSUM
0xA5:
The first byte sent in the response is byte with HEX value of 0xA5.
ID:
Exactly two bytes long. This is the unit ID written as two ASCII characters.
For example, if the unit ID is 2, then ID will be sent as “02”. In HEX
representation it is the following two bytes: <0x30><0x32>.
SPEED:
The speed readout in currently selected units, formatted as real (float)
number with exactly three digits after the decimal dot separator.
For example, if the current averaged speed is 5.7143, it will be reported as
5.714, or in HEX values: <0x35><0x2E><0x37><0x31><0x34><0x33>.
LEVEL:
The level readout in meters, formatted as a real (float) number with exactly three
digits after the decimal dot separator. For example, if the current averaged level is
5.7143, it will be reported as 5.714, or in HEX values:
<0x35><0x2E><0x37><0x31><0x34><0x33>.
CSUM:
Checksum, calculated by adding in modulo 256 the two byte values of the ID and
all byte values from the SPEED.
Summary of Contents for GLX-RSS-2-300 WL
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