How To Use The RS485 Interface of Load Cell Transmitter?
A load cell is actually a device that converts a mass signal into measurable electrical output. ATO has introduced how to convert the mV model output by the pressure sensor into a 4-20mA standard analog signal. But in the industrial control process, digital signals are also extremely important, so this time ATO will explain the RS485 interface function ( Modbus RTU protocol ) of the load cell transmitter.
Remove the casing and connect the load cell line and communication line. Just like connecting to other display controllers or transmitters, the SIG+, SIG-, EXC+, and EXC- of the load cell need to be connected to the transmitter. The other end is a 24VDC power supply interface and a digital signal output.
We also need to use an RS485 to USB converter so that the digital signal can be viewed on the PC side.
Step 1: enter the parameter interface, find "ZERO", press "˅" to enter the parameter setting, press "˄" to clear, and then press "□" to return.
Step 2: select "CAP", press "˅" to enter the parameter setting, and put the 2kg weight on the load cell, set the parameter to 2.00, and press "□" to confirm and return.
Step 3: set the parameter interface, select "09" bps=3 (9600bps) "10"=0 (slave mode, receive commands and send responses)
"10"=0 (slave mode, issue responds after receiving an instruction).
"11"=0 (8 data bits, 2 stop bits)
"11" = 0 (data bit is 8, stop bit is 2).
"12"=1 (meter ID)
"12" = 1 (meter ID).
Then, press "˄" to return to the interface. It is finished.
Step 1: fill in the COM port, baud rate, and other communication information first.
Step 2: Then open the serial port and send a message to read the current weight data 01 03 00 00 00 01. There is no heavy object on the current load cell, so the current data read is 00 00.
Step 3: put a 2kg weight and read the current data again. The weight data is 00 C8 (hexadecimal) = 200 (decimal).
Step 4: put a 0.13kg weight and read the weight data. Weight data is 00 0D (hexadecimal) = 13 (decimal).
The above is a simple function of reading data using the Modbus RTU protocol. However, each company has different protocol content definitions for their products. Therefore, every time a new product needs to use the Modbus RTU protocol, it must be read the function code of the communication protocol carefully.
Please watch the video below for more details.
ATO.com offers a wide selection of high-performance digital load cells at affordable factory prices. Let's try to use the RS485 interface of the ATO load cell transmitter.