I have recently brought a Modbus rtu humidity temperature unit (PKTH100B-CZ1) can I just conect it to com port 1 (c1/c2) and use the modbus master command or do I need a 485 to rs232 convertor
Hi
yes you need to convert from RS485 to RS232.
From CR800 manual:
"The CR800 supports Modbus master and Modbus slave communications for
inclusion in Modbus SCADA networks. Modbus is a widely used SCADA
communication protocol that facilitates exchange of information and data between
computers / HMI software, instruments (RTUs) and Modbus-compatible sensors.
The CR800 communicates with Modbus over RS-232, (with a RS-232 to RS485 such as an MD485 adapter), and TCP.
Modbus systems consist of a master (PC), RTU / PLC slaves, field instruments
(sensors), and the communication-network hardware. The communication port,
baud rate, data bits, stop bits, and parity are set in the Modbus driver of the master
and / or the slaves. The CR800 supports RTU and ASCII communication modes
on RS-232 and RS485 connections. It exclusively uses the TCP mode on IP
connections."
Smile