ROTRONIC MBW 373 - Manual (Page 27)

23
Back Panel Connections
Power Plug
The power requirements are identified on the serial number label on the back of the instrument.
Depending on the model, fuse access may also be available on or near the power plug.
Power Switch
Depending on the model, the main power switch will either be mounted on the front panel (L and
LX models), or on the back panel near the power plug. Use the power switch to turn the system
ON and OFF.
The 373L and LX models contain a refrigeration compressor that is electrically protected with a
circuit breaker mounted on the back panel above the power plug. The breaker connects to the
refrigeration compressor only and does not affect power to any other part of the system. To use
the pre-cooler, this circuit breaker must be ON.
RS-232
The RS-232 connector is used when connecting the 373 to an external computer. Use a
standard 9 pin cable to connect between the 373 and a desktop or laptop computer. The cable
is wired straight through with pins 1 through 9 of the male end wired to pins 1 through 9
respectively of the female end. The RS-232 extender cable is a common accessory item easily
obtained at most any computer accessory dealer.
See Remote Communication on page 33 for complete discussion of the RS-232 command
reference and hardware connections.
External Temperature
The External Temperature plug on the back panel is used for connection of an external
temperature probe. External temperature measurements are required if certain humidity
parameters are to be computed, such as %RH. External temperature measurements are not
required for dew or frost point measurements.
If you wish to connect your own thermometers, the 373 requires a 5 pin connector, LEMO
(www.lemo.ch) part number FGG 1B 305 CLAD 42. When wiring the cable, note that pin
numbering of the socket in the back panel starts at the top and goes counter-clockwise (as
viewed from the rear of the unit). ). When viewing the solder tubs of a disassembled 5-pin
LEMO connector, pin 1 is usually identified with a full or partial circle drawn around it. After
identifying pin 1, follow the line counter-clockwise from pin 1 to all other pins in succession. Wire
the cable according to the following:
Pin Signal Position
1 Shield
2 +I
3 +V
4 -V
5 -I
1
2
3 4
5
When the 5-pin LEMO connector is properly assembled, you will notice that the red dot of the
connector housing will be aligned at the top directly above pin 1.