Vaisala HMP260 - Manual (Page 103)

HMP260 SERIES
HMP260-U017en-1.5 Appendix 4: Digital current loop module
2 OPERATION
The HMP260 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 HMP260 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 a HMP260 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
HMP 230 TYPE
TRANSMITTERS
1 TO N PIECES
+
DUAL LOOP WIRING
TWISTED PAIR WIRING
CURRENT
LIMIT
LOOP
SUPPLY
-
HOST COMPUTER
HMP 230 TYPE
TRANSMITTERS
1 TO N PIECES
+
NOTE : HALF DUPLEX DATA TRANSFER.
HMP 230 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 -