Ametek 7230 - Chapter 6 Computer Operation; RS232 Operation

Computer Operation
Chapter 6
6-1
6.1 Introduction
The model 7230 includes RS232, USB and Ethernet interface ports, designed to
allow it to be completely controlled from a remote computer. All of the instrument's
controls may be operated, and all of the outputs can be read, via these interfaces.
This chapter describes the capabilities of the instrument when operated remotely and
discusses how this is done. Refer to Chapter 5 for a description of how to operate the
instrument via its built in web control panels.
6.2 Capabilities
6.2.01 General
All instrument controls can be set, with the exception of the functions selected by the
rear panel CONFIG switches, and all instrument outputs may be read remotely.
6.2.02 Operation
Control of the lock-in amplifier from a computer consists of the computer sending
commands to the instrument, with it responding either by sending back some data or
by changing the setting of one of its controls. The commands and responses are
generally ASCII text strings, although transfer of data from the instrument’s curve
buffer can also be done using a binary dump of values, with each value being two
bytes long.
The computer ports cannot be used simultaneously, but when a command has been
completed, the lock-in amplifier will accept the next command from any port, and
respond to that port.
6.2.03 Compound Commands
Unlike some older SIGNAL RECOVERY instruments, the model 7230 does not
support compound commands, which were two or more simple commands separated
by semicolons (ASCII 59) and terminated by a single command terminator.
6.3 RS232 Operation
6.3.01 Introduction
The RS232 interface is primarily intended to enable the lock-in amplifier to be
operated from a computer program specially written for an application, although it
can also be used in the direct, or terminal, mode. In this mode the user enters
commands on a keyboard and reads the results from the display.
The simplest way to establish this terminal mode is to connect the instrument to a
computer running a terminal emulator, such Windows HyperTerminal.
6.3.02 General Features
The RS232 interface in the model 7230 is implemented with three wires; one carries
digital transmissions from the computer to the lock-in amplifier, the second carries
digital transmissions from the lock-in amplifier to the computer and the third is the
Logic Ground to which both signals are referred. The logic levels are ±12 V referred
to Logic Ground, and the connection may be a standard RS232 cable in conjunction