Vaisala HMP230 - Manual (Page 125)

HMP230 SERIES
M210225en-B Appendix 4: Digital current loop module
119
2. OPERATION
The HMP230 transmitters can either be given an address or operated without
an address. Both single and dual loop wiring with half duplex connection can
be used. No address is needed when only one HMP230 transmitter is used;
when several transmitters are connected to the same line, each transmitter
must be given an address in the initial configuration.
A current loop must get its operating voltage from the master or it can have its
own (floating) power supply capable of supplying 15...40 V and 20...30 mA.
Unregulated AC/DC adapter can be used, if the current is limited to 20 mA at
least by a serial resistor.
NOTE: The host computer can restrict the loop supply voltage that can be
used; see computer specifications.
The serial line structure is a serial interfaced chain (daisy chain). At one end
of the serial line there must be an HMP230 transmitter and at the other end a
line master. A branch line can be made with a junction box.
+
SINGLE LOOP WIRING
TWISTED PAIR WIRING
CURRENT
LIMIT
LOOP
SUPPLY -
HOST COMPUTER
HMP230 TYPE
TRANSMITTERS
1 TO N PIECES
+
DUAL LOOP WIRING
TWISTED PAIR WIRING
CURRENT
LIMIT
LOOP
SUPPLY
-
HOST COMPUTER
HMP230 TYPE
TRANSMITTERS
1 TO N PIECES +
NOTE : HALF DUPLEX DATA TRANSFER.
HMP230 DOES NOT RECEIVE WHILE
TRANSMITTING VIA SERIAL PORT MODULE .
RX -
RX +
TX +
TX -
RX -
RX +
TX +
TX -
RX -
RX +
TX +
TX -
RX -
RX +
TX +
TX -
RX -
RX +
TX +
TX -
RX -
RX +
TX +
TX -