C
Y
K
Tech
www.ceyeko.com
Page 53
Fig. 12 Echo when Probe is Out of Connecting Pipe
After the ultrasonic level gauge is taken out of the connecting pipe, the base line
narrows obviously and becomes normal. The echo in circle will be much higher than
the base line.
Chapter 9: Modbus Communication Protocol V1.4 Version
Modbus RTU mode communication protocol
1. The hardware adopts rs-485, master-slave half-duplex communication, the host
calls the slave address, and the slave responds mode communication.
2. Data frame 10 bits, 1 start bit, 8 data bits, 1 stop bit, no parity.
3. Baud rate: 2400 4800 9600 19200 (default is 9600)
4. Function code 03h: read register value
1
2
3
4
5
6
7
8
ADR
03H
Start re-
gister
high byte
Start re-
gister low
byte
Number
of regis-
ters high
byte
Register
number
low byte
Crc code
low byte
Crc code
high byte
1st byte adr: slave address code (=001~254)
2nd byte 03h: read register value function code
3rd, 4th byte: Register start address to be read
5th, 6th byte: number of registers to read
7th, 8th byte: crc16 check from byte 1 to 6