Instructions

8 Digital Communications Interface
8.1 Overview
The communication features allow an external device, such as a computer, to
communicate with the Thermo-Hygrometer readout to receive measurement
data and control operating settings. Communication is accomplished by issuing
commands to the Thermo-Hygrometer through an RS-232, RF wireless (op
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tional), or Ethernet LAN interface.
8.1.1 Serial RS-232
A serial RS-232 interface allows connection between the instrument and a stan
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dard COM port on one computer or terminal through a three-conductor cable
up to distances of 50 feet, typically.
The serial cable attaches to the Thermo-Hygrometer readout through the
RS-232 port on the left side of the instrument. Figure 48 shows the pin-out of
this connector and suggested cable wiring. Note the TxD line on one side con
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nects to the RxD line on the other side and vice-versa. To avoid electromag
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netic interference, 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 programmable. Re
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fer to Section 7.5.3, Comm Setting, for instructions on setting these parameters.
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8 Digital Communications Interface
Overview
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2
3
4
5
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7
8
9
RxD
TxD
GND
RxD
TxD
GND
Figure 48 Serial Cable Wiring