Longrun LRF-3000S - Communication Protocols (HL, MODBUS-I)

LRF-3000S Ultrasonic Transit-time Flow meter
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8.3. Direct connection via RS232 to the host device
See the below list of flowmeter serial port definitions.
8.4. Communications protocol and the use
The flow meter supports these three communication protocols: FUJI Protocol, MODBUS-C Protocol, MODBUS-I
Protocol.
8.4.1. HL Protocol
The communication protocol format used by the ultrasonic flow meter is an expanded set of the HL FLV series
flow meter protocol. The host device requests the flow meter to answer by sending a "command". The baud rate of
asynchronous communication (Primary station: computer system; Secondary station: ultrasonic flow meter) is
generally 9600BPS. A single byte data format (10 bits): one start bit, one stop bit and 8 data bits. Check bit: none.
A data character string is used to express basic commands and a carriage return (ENTER) is used to express the
end of a command. The characteristic is that the string of data is flexible. The order applies to both RS232 and
RS485. Frequently used commands are as follows:
Communications commands
Command
Description
Data format
RFR(cr)(lf)
Return instantaneous flow
±d.ddddddE±dd(cr) Note1
RVV(cr)(lf)
Return instantaneous velocity
±d.ddddddE±dd(cr)
RT+(cr)(lf)
Return positive accumulative flow
±ddddddd.dE±d(cr) Note 2