SR05-D1A3-PV manual v1801 53/83
6.5 Network communication: getting started
Once it has the correct Modbus address and communication settings, SR05-D1A3-PV can
be connected directly to an RS-485 network and a power supply. How to physically
connect a sensor as a slave in a Modbus network is shown in section 5.11: Connecting a
SR05-D1A3-PV to an RS-485 network. In such a connection the sensor is powered via an
external power supply of 5 to 30 VDC. When the sensor is bolted onto a grounded
mounting plate, which is usually the case, the shield is not connected to ground at the
cable end.
Installing a SR05-D1A3-PV in the network also requires configuring the communication
for this new Modbus device. This usually consists of defining a request that can be
broadcast by the master. If the SR05-D1A3-PV is not already defined as a standard
sensor type on the network, contact the supplier of the network equipment to see if a
library file for the SR05-D1A3-PV is available.
Typical operation requires the master to make a request of irradiance data in registers
0x1002 + 0x1003, sensor temperature in register 0x1006, and the sensor serial number
in register 0x1028 every 1 second, and store the 60 second averages. The data format of
register 0x1002 + 0x1003 is a signed 32 bit integer and the temperature in register
0x1006 is a signed 16 bit integer.
Up to five 16 bit registers can be requested in one request. In case six or more registers
are requested in just one request, SR05-D1A3-PV will not respond. If requesting six or
more registers, multiple requests should be used: SR05-D1A3-PV will respond as
expected.
6.5.1 Adapting Modbus address and communication settings
Setting the instrument address and baud rate can be done in different ways:
• by connecting the sensor to the PC and using the Sensor Manager;
• by connecting the sensor to the PC and using another Modbus testing tool. There are
links to different solutions available at www.modbus.org
;
• by using the available network user interface software.
The Modbus address is stored in register 0x1000 and has a default value of 1. A user
may change the address to a value in the range of 1 to 247. The address value must be
unique in the network. The communication settings are stored in register 0x1001. The
default setting is setting number 1 representing a communication with 9600 baud, no
parity bit, 8 data bits and 1 stop bit. After a new address or communication setting is
written the sensor must be restarted. This can be done by writing 0XFF00 to coil 0.
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