Vaisala PTB220 - Manual (Page 97)

A PPENDIX F _________________________________ MULTIPLE PTB220 BAROMETERS ON RS 232 C
V AISALA _________________________________________________________________________ 91
APPENDIX F MULTIPLE PTB220 BAROMETERS ON
RS232C
It is possible to connect multiple PTB220 series digital barometers on
one RS232C interface for example for fine adjustment and calibration
of several barometers in one batch. The PTB220 series barometers
have a special transmission terminal for this kind of use as pin 1 (TX
with diode) has a built-in diode in series with the TX line. The diode
protects the output stage of a barometer when some other PTB220
series barometer is speaking on the line.
The host computer must have adequate buffering to be able to handle
multiple PTB220 series barometers.
GND
GND
TX WITH DIODE
RX
GND
RX
GND
RX
TX
HOST
COMPUTER
TX WITH DIODE
TX WITH DIODE
PTB220 # 1
PTB220 # 2
PTB220 # 3
RX
To be able to use multiple PTB220 series barometers on one RS232C
interface the user must first set an address for each barometer and then
activate the POLL/CLOSE mode. Then the barometers can be
connected to the same RS232C interface and they can be polled by the
SEND command or by using the OPEN/POLL commands. See
Chapter Operating modes, SMODE command and Chapter POLL
mode, SEND and OPEN/CLOSE commands for information on how
to set and use the PTB220 series barometers in POLL mode.
Example of required software commands:
>smode
Serial mode
: STOP
>addr 7
Address
: 7
>smode poll
Serial mode
: POLL
>close
line closed
send 7
(text invisible)
1013.25 hPa