User’s Manual UT5583 Insulation Resistance Tester
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13. Remote Communication
13.1 RS-232C Interface Setting
13.1.1 RS-232 Introduction
RS-232 is widely used serial communication standard, it’s also called asynchronous serial communication
standard. It’s used to to realize data communication between computers and peripherals. RS is English
abbreviation of “Recommended Standard”, 232 is standard number. The criterion is officialy published by
Electronic Industries Alliance (EIA) in 1969. It requires that each bit should via a data line to transmit.
But the configuration of most serial ports is usually not strictly based on the RS-232 standard: a 25-core
connector is used in each port (today's computers basically use a 9-core connector). The common RS-232
signal as shown in the following table.
Table 13-1 Common RS-232 Signal
Signal
Symbol
Pin number of 25-core
connector
Pin number of 9-
core connector
Request to send
RTS
4
7
Clear to send
CTS
5
8
Data set ready
DSR
6
6
Data carrier detect
DCD
8
1
Data terminal ready
DTR
20
4
Transmit data
TXD
2
3
Receive data
RXD
3
2
Ground
GND
7
5
Request to send
RTS
4
7
In addition, there is a minimal subset of RS232, which the connecting way of the instrument.
Table 13-2 Standard Minimum Subset of RS-232
Signal
Symbol
Pin number of 9-core connector
Transmit data
TXD
2
Receive data
RXD
3
Ground
GND
5
13.1.2 RS-232 Connection
Suggestion: In order to prevent electric shock, please turn off the power when plug the
connector.
