Teledyne 2000A-EU, Руководство по эксплуатации, Страница: 61 / 86

Thermal Conductivity Analyzer Operation 4
4-23
Teledyne Analytical Instruments
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 program-
ming subfunction and the Range button function, which is an
operator control. The Set Range Screen of the
System func-
tion 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 2000 is factory set to default to manual range selec-
tion, 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.
MODEL APPLICATION
SELF_TEST ALGORITHM