Campbell Scientific HMP155A Temperature and Relative Humidity Probe - Manual (Page 40)

Appendix C. Interfacing with HMP155A RS-485 Output
C.3 MD485 Multidrop Interface Option
The MD485 Multidrop Interface can be used to interface the RS-485 outputs of
the HMP155A to the datalogger’s CS I/O port. Connect the MD485’s CS I/O
port to the datalogger’s CS I/O port with an SC12 cable. Sensor wiring to the
MD485 and the datalogger is documented in the example program below.
The HMP155A has a default RS-485 baud rate of 4800, which must be
changed to 9600 to be compatible with the MD485. To change settings in the
HMP155A, Vaisala’s USB to RS-485 cable is required to interface the
HMP155A sensor to a computer. Commands to change settings are sent to the
HMP155A using a terminal emulator such as Windows HyperTerm.
Vaisala’s USB to RS-485 cable includes a CD with drivers that must be
installed on the computer before the cable can be used. Insert the CD into the
computer’s CD drive and follow the prompts.
C-4