Specifications

APPLICATION NOTE

Using the SUTRON RADAR LEVEL CONTROLLER (RLR-0002-1) with a MULTI-MODEM GPRS

(Wireless Modem MTCBA-G-F4)

From the factory, the default baud rate setting in the radar level sensor is 115200. The modem

baud rate is set to 9600. To change the radar level sensor baud rate, press the down arrow to

Station Setup then press the right arrow. Press the down arrow to Other Settings then press the

right arrow. Press the down arrow to Baud Rate then select 9600.

Now you are ready to connect the GSM modem to the Radar Level Recorder.

2.4 MODBUS INTERFACE

This section illustrates how to configure the GSM modem and Radar Level Sensor for MODBUS

interface and explain how to configure AutoPoll program to support MODBUS.

MODBUS is a standard communication protocol supported by several Sutron loggers (See

www.MODBUS.org).

AutoPoll is a program for the PC used to perform scheduled remote data collection from Sutron

data loggers. AutoPoll supports multiple protocols, including MODBUS. AutoPoll download

data .LOG files from the Radar Level Recorder. This downloaded data is saved in your PC as

.CSV file.

(See : http://www.sutron.com/beta/AutoPoll/AutoPoll.htm for more information)

2.4.1 GSM Modem AT commands- MODBUS

The following AT commands are required to program the GSM modem so the modem

can communicate properly with the PC via MODBUS interface.

First, you have to connect the GSM modem to a PC and configure the modem using

Hyper Terminal in Windows. You must use a RS 232 serial cable to connect the GSM

modem to a PC.

Type a <Enter> after each command.

AT+VGR=1 (Use to tune the receive gain of the speakers)

AT+VGT=255 (Use to tune the transmit gain of the microphone)

AT+CBST=0,0,1 (0 = Autobauding, 0 = only asynchronous modem, 1=Non

transparent only)

AT+IPR=9600 (Data rate at which the modem will accept commands)

AT+ICF=3,4 (Character framing modem serial port 3= 8 Data 1 stop, 4=

None)

AT+IFC=0,0 (Hardware flow control mode 0= none, 0= none)

AT+FCLASS=0 (0 = Data operating mode)

AT+CSNS=4 (Select de bearer 4=data)

ATS0=1 (Numbers of rings before automatic answer)

AT&D2 (Upon DTR switch from ON to OFF, the call id release)

AT&C1 (Controls Data Carrier Detect Signal (DCD) )

ATQ1 (1 = Result codes suppressed, no transmitted)

AT&W (Save configuration)

The modem is now configured for use with the Radar Level Recorder and Autopoll using

MODBUS over the GSM modem. To verify this configuration use “AT&V” command.

This should show:

AT&V

Q:1 V:1 S0:001 S2:043 S3:013 S4:010 S5:008