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Micro-Bath
Serial Communications
Serial Communications
The calibrator has an RS-232 serial interface that allows serial digital communications over fairly long
distances. Use a serial interface to access any of the functions, parameters, and settings discussed in
except for the BAUD rate setting.
Wiring
The serial communications cable attaches to the calibrator through the DB-9 connector at the back of
the instrument. Figure
7
shows the pin-out of this connector and suggested cable wiring. To eliminate
noise, the serial cable should be shielded with low resistance between the connector (DB-9) and the
shield. If the unit is used in a heavy industrial setting, the serial cable length must be limited to 1 Meter.
Setup
Before operation, first set up the serial interface by programming the BAUD rate and other
configuration parameters. Program these parameters within the serial interface menu. The serial
interface parameters menu is outlined in Figure 6. Refer to
Serial Interface Parameters
for BAUD Rate,
Sample Period, Duplex Mode, and Linefeed.
To enter the serial parameter programming mode:
1. Push EXIT while you push SET, and then release to enter the secondary menu.
2. Push SET repeatedly until the display reads PAr.
3. Push UP until the serial interface menu is indicated with Serial.
4. Push SET to enter the serial parameter menu. The BAUD rate, the sample rate, the duplex mode,
and the linefeed parameter are in the serial interface parameters menu.
Serial Operation
Once the cable has been attached and the interface set up properly, the controller immediately begins
to transmit temperature readings at the programmed rate. Serial communications uses 8 data bits, one
stop bit, and no parity. The set-point and other commands can be sent through the serial interface to
set the temperature set-point and view or program the various parameters. The interface commands
are discussed in
Interface
Commands. All commands are ASCII character strings terminated with a
carriage-return character (CR, ASCII 13).
Interface Commands
The various commands to access calibrator functions through the digital interface are listed in this
section (see Table 5). These commands are used with the RS-232 serial interface. Terminate the
commands with a carriage-return character. The interface makes no distinction between upper- and
lower-case letters, hence either can be used. Commands can be abbreviated to the minimum number
of letters which determines a unique command. A command may be used to either set a parameter or
display a parameter depending on whether there is a value sent with the command following a =
character. For example, s <CR > returns the current set-point and s =150.0<CR> sets the set-point to
150.0 degrees.
In the list of commands in Table 5, characters or data within brackets, [ and ], are optional for the
command. A slash, /, denotes alternate characters or data. Numeric data, denoted by n, can be
entered in decimal or exponential notation. Characters are shown in lower case although upper case
may be used. Spaces may be added within command strings and will simply be ignored. Backspace
(BS, ASCII 8) may be used to erase the previous character. A terminating CR is implied with all
commands.
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