Vaisala HMP240 - Manual (Page 104)

HMP240
Appendix 3: Digital current loop module
M210300en
102
APPENDIX 3: INSTALLING AND USING THE DIGITAL CURRENT
LOOP MODULE
INSTALLATION
Switch the transmitter off.
Resistors R2, R3 and R4 between connectors X4 and X5 in the component
board in the cover of the transmitter are removed with side-cutting pliers. The
module is plugged in connectors X4 and X5 on the main board of the HMP240
transmitter; connector X1 on the module board to connector X4 and connector
X2 to connector X5.
RX GND TX
R2
R3
R4
X6
RX +
TX +
X4 X5
Current loop
module
X1 X2
D
A
T
A
L
O
O
P
S
TX -
RX -
X17
Connect the data wires to screw terminal X6 on the main board. Switch the
power on.
OPERATION
The HMP240 transmitter 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 HMP240 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.