For a guide to setting up and testing Modbus RTU (serial, RS485) communication on your RC18 PV reference cell, use the link at the bottom of the page to download our application note document 880083. 

This guide provides examples for setting up third-party Modbus testing software, such as ModbusPoll, to establish communication and data retrieval from your RC18 unit. The examples in the guide highlight important parameter settings which may help you to set up your own data logging or SCADA system.  

For a complete list of RC18 Modbus registers, see the RC18 User Guide.