Teledyne 2020 - Explosion proof thermal conductivity analyzer - Manual (Page 58)

4 Operation Model 2020
4-24 Teledyne Analytical Instruments
4.8.1 The Set Application Screen
The Set Application 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 pro-
gramming is usually done at the factory according to the customer’s appli-
cation. 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 program-
ming subfunction and the Range button function, which is an
operator control. The Set Range Screen of the Application
function allows the user to DEFINE the upper and lower limits
of a range AND the application of the range. The
Range func-
tion only allows the user to select or define the limits, or to
select the application, but not to define the application.
Normally the Model 2020 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 sensitivi-
ty. 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 corresponding 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
concentration 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 concentra-
tion are unaffected by the fixed range. They continue to read beyond the
full-scale setting until amplifier saturation is reached. Below amplifier
saturation, the over range 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 MAIN
MENU and selecting application function screen.
Sel rng to set appl:
—> Ш1 Ш2 Ш3 CAL <—