8
Digital Communications Interface
8.1
Overview
The communication feature allows an external device, such as a computer, to
communicate with the thermo-hygrometer readout to obtain measurement data
and control operation settings. Communication is accomplished by issuing
commands to the thermo-hygrometer readout through RS-232 or IR
communication ports.
8.2
Communications
The thermo-hygrometer readout is equipped with an RS-232 serial interface
and an infrared window. The serial interface allows communications up to dis-
tances of approximately 50 feet. The IR interface allows close proximity,
line-of-sight, wireless communications. The serial interface and infrared win-
dow allow the user to access the functions, parameters, and settings discussed
in Section 7.5.3, Comm Setting.
8.2.1
Serial Wiring
The serial communications cable at-
taches to the thermo-hygrometer
readout through the RS-232 port on
the left side of the instrument. Figure
50 shows the pin-out of this connec-
tor and suggested cable wiring. Note
the TxD line on one side connects to
the RxD line on the other side and
vice-versa. To eliminate noise, the
serial cable should be shielded with
low resistance between the connector
and the shield.
The serial period, baud rate, linefeed,
and echo (duplex) are programma-
ble. Refer to Section 7.5.3, Comm
Setting, for instructions on accessing
and setting these parameters.
All commands sent to the thermo-hy-
grometer readout through the serial interface must be terminated with a carriage
return (ASCII 0D hex, 13 decimal) or new line character (ASCII 0A hex, 10
decimal).
1620 the “DewK”
75
8 Digital Communications Interface
1
2
3
4
5
6
7
8
9
RxD
TxD
GND
RxD
TxD
GND
Figure 50
Serial Cable Wiring
