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Typical operations with an external computer
Since the instrument can save a large number (usually 500) of sample measurements, this
data is usually transferred from the instrument to a larger computer for analysis. The
command set of the instrument allows the external computer to read the stored samples
and reset the storage of the instrument.
The instrument contains a number of operation defaults which can be examined and
changed over the communication link.
An external computer may set standards into the instrument and may also set Pass/Fail
limits for the standards. When this is done there is no operation of the instrument required
during the time that the instrument is connected to the external computer. When the
instrument is used as a portable again, the standards may appear with text names in the
select standard menu items and in the color difference vs. standard display.
An external computer may also be used with a reference spectrophotometer or with
numerical and physical standards to establish an application specific greyscale for the
instrument. This process usually requires that the instrument take measurements under
the control of the external computer. In some cases the instrument will act as a measuring
device for an application which executes in an external computer. Also in this case, the
instrument must perform measurements under the control of a personal computer.
The instrument may be asked to perform a measurement by an external computer in two
different ways. The external computer may tell the instrument to measure now, or the
external computer may tell the instrument to measure when the operator is ready. We call
the first type of measurement MEASURE IMMEDIATE, and the second type
PROMPTED MEASURE.
The operation of the instrument under external control is slightly different than operation
as a stand alone unit. As soon as the instrument sees any command from the external
connector which indicates that an external computer is present and attempting to control
the instrument, it changes the RDY/Measure message to
Under PC Control
or
PC
RDY/Measure
. The external computer may send specific commands to release PC
control, or the operator may force a communications reset from the instrument keyboard,
or the operator may force a power cycle at the instrument. Until one of these events
occurs the instrument will remain Under PC Control. When the instrument is Under PC
Control, the green
DO
key will not initiate measurements unless specifically instructed to
do so by the external computer. When the external computer requests a MEASURE
IMMEDIATE the display of the instrument will read
REMOTE MEASURE
during the
measurement and change to PC RDY/Measure when complete.
When the external computer requests a PROMPTED MEASURE, the display of the
instrument will read
Waiting/Measure
until the operator starts the measurement by
pressing the green
DO
key. The display will read Measuring until the measurement is
complete.
