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Thermal Conductivity Analyzer Part I: Control Unit
Part I 4-23
Teledyne Analytical Instruments
MODEL APPLICATION
SELF_TEST ALGORITHM
Now you will be able to select the APPLICATION and ALGORITHM
set-up functions.
4.8.1 The Set Range Screen
The Set Range screen allows reprogramming of the three analysis ranges
and the calibration range (including impurity gas, background gas, low end of
range, high end of range, and % or ppm units). Original programming is usually
done at the factory according to the customer’s application. It must be done
through the RS-232 port using a computer running a terminal emulation program.
Note: It is important to distinguish between this
System
programming
subfunction and the
Range
button function, which is an operator
control. The Set Range Screen of the
System
function allows the user
to DEFINE the upper and lower limits of a range AND the application
of the range. The
Range
button function only allows the user to
select or define the limits, or to select the application, but not
to define the application.
Normally the Model 2010B is factory set to default to manual range
selection, unless it is ordered as a single-application multiple-range unit (in which
case it defaults to autoranging). In either case, autoranging or manual range
selection can be programmed by the user.
In the autoranging mode, the microprocessor automatically responds to
concentration changes by switching ranges for optimum readout sensitivity. If the
upper limit of the operating range is reached, the instrument automatically shifts
to the next higher range. If the concentration falls to below 85% of full scale of
the next lower range, the instrument switches to the lower range. A correspond-
ing shift in the DC concentration output, and in the range ID outputs, will be
noticed.
The autoranging feature can be overridden so that analog output stays on a
fixed range regardless of the contaminant concentration detected. If the concen-
tration exceeds the upper limit of the range, the DC output will saturate at 1 V dc
(20 mA at the current output).
However, the digital readout and the RS-232 output of the concentration
are unaffected by the fixed range. They continue to read beyond the full-scale
setting until amplifier saturation is reached. Below amplifier saturation, the
overrange readings are accurate UNLESS the application uses linearization over
the selected range.
To program the ranges, you must first perform the four steps indicated at
the beginning of section 4.8 Programming. You will then be in the second
System
menu screen.