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8.3 Communication Protocol and its Use
The flowmeter supports HL protocol and MODBUS protocol.
8.3.1. HL protocol
The flowmeter applies HL communication protocol. The host device would request the flowmeter
to respond after sending a “command”. Asynchronous communication baud rate (Main station:
computer system; secondary station: ultrasound flowmeter) is 9,600 BPS in general.
Single byte data format (10 bits): One start bit, one stop bit and eight data bits. Check bit: Non.
One data character string is used for indicating the basic command, while one ENTER is used for
indicating ending the command. This command is applicable for RS232 and RS485. Common
commands are shown below:
Common Communication Commands
Command
Description
Data format
RFR(cr)(lf)
Return to Transient Flow
±d.ddddddE±dd(cr) Note 1
RVV(cr)(lf)
Return to Transient Velocity
±d.ddddddE±dd(cr)
RT+(cr)(lf)
Return to POS Total
±ddddddd.dE±d(cr) Note 2
RT-(cr)(lf)
Return to NEG Total
±ddddddd.d±d(cr)
RTN(cr)(lf)
Return to NET Total
±ddddddd.d±d(cr)
RTH(cr)(lf)
Return to Total (Heat Quantity)
±ddddddd.d±d(cr)
RTC-(cr)(lf)
Return to Total (Cool Quantity)
±ddddddd.d±d(cr)
RER(cr)(lf)
Return to Energy Transient Quantity
±d.ddddddE±dd(cr)
P
With check return command prefix
Note 5
W
Network command prefix of digit string
address
Note 6
Annotations:
1.
(cr) indicates ENTER, its ASCII code value is ODH. (If) indicates changing a line and its ASCII
code value is OAH.
2.
“d” indicates
0~9 digits and 0 is expressed by + 0.0 00.
3.
“d” indicates
0~9 digits and the integral part has no decimal point.
4.
dddddddd indicates the electronic serial number of the machine.
5.
Character P could be added before every basic command, it indicates the feedback data has
CRC check. The check sum is obtained through binary addition, which is a cumsum binary
system taking the least 8-bit binary data.
For example: Feedback information RT(cr)(lf): +10m3(cr)(lf)(corresponding binary
data are 2BH, 31H, 32H, 33H, 34H, 35H, 36H, 37H, 45H, 2BH, 30H, 6DH, 33H, 20H, 0DH, 0AH )
