Chapter 4_________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 49
When separate heater power is applied, it can be used to supply
internal heaters, that is, including PWL111 heaters. In this case
separate heater voltage must not exceed 28 V (24 V recommended).
Hood Heaters PWH111
A separate heating power of 24 V must be applied when using hood
heaters . They use 30 W each, which is 60 W altogether. If PWL111
and PWD22 internal heaters are powered by this same supply, it is
loaded by approximately 65 W.
Communication Options
PWD22 has one serial line with two interfaces. The two-wire RS-485
is intended to be the standard interface. The PWD22 software is
designed to allow the RS-232 interface to be used as a service line,
when the RS-485 interface is connected to the host computer.
Usually, PWD22 waits for input from both the RS-232 and RS-485
interfaces. Any character from the RS-232 interface disables the RS-
485 communication for 10 seconds or until the line is closed by the
operator.
Automatic messages are sent to both interfaces along with the
messages polled from the RS-485 interface.
Serial Communication Settings
The default settings of the serial communications port are as follows:
- 9600 baud
- Even parity
- 7 data bits
- 1 stop bit
Serial Transmission RS-232
For the RS-232 communication connect the PWD22 signal wires to:
- YEL
to PC 3/9: TxD RS-232
- GRN
to PC 2/9: RxD RS-232
- GRY
to PC 5/9: GND
