720A Operation and Maintenance Manual – Rev S – January 25, 2019
Page 19
13231 Rooster Springs Rd.,
Austin, TX 78737
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amptec.com
D-7 Detailed Use Description for RS-232C Function
The RS-232C Interface for the AMPTEC 720A Digital Micro-Ohmmeter allows the user
to communicate with the meter through a serial connection from a computer. The RS-
232 communication interface can be used to switch measurement ranges, query
resistance readings from the meter, and read the firmware version of the meter. Any
software application that can send and receive serial communication messages can be
used to communicate with your 720A meter (e.g. HyperTerminal, PuTTY, Termite).
Once the communication protocol settings (listed in section D-7.1) are met, the meter
should be connected to a computer using a DE-9 connector. Most modern computers
do not have a built-in DE-9 serial port, but a USB-to-DE-9 converter will work if properly
installed. If a command is sent from the user to the meter, the meter will respond that a
command has been received. To test that your unit and the computer are connected
correctly, send a “V” command to read the firmware version back from the meter.
Additional commands are listed in the following section D-7.1.
Note: Readings taken through the RS-232C communication interface may be from
either the front or rear panel.
D-7.1 RS-232C Commands and Data Format
This section details the commands necessary to communicate with your 720A meter via
its RS-232C connection. The RS-232C communication protocol for the 720A is listed
below:
Baud Rate: 9600
Data Bits: 8
Stop Bits: 1
Parity: None
Please note that the RS-232C Interface will not function correctly unless all the physical
range selection buttons are deselected (all the way out).
RS-232C Commands
Please note that the following commands are case-sensitive.
C
Continuous Read Mode: Meter will output readings to computer for every reading
computed by the digital voltmeter (DVM). To turn this mode off, enter a ‘S’
command to switch to Single Read Mode.
S
Single Read Mode: Meter will output one reading every time it receives a ‘R’
command from the computer. User must enter this command to turn off Continuous
Read Mode. Meter is in Single Read Mode by default.
R
Read Command: When in Single Read Mode, meter will output one reading when
this command is received. When in Continuous Read Mode, this command will not
appear to have any effect.
