Teledyne 6020 - Photometric analyzer - Manual (Page 48)

3 Operation Model 6020
3-24 Part I
Teledyne Analytical Instruments
3.6.2 Auto Screen
Autoranging will automatically set to the application that has at least two
ranges setup with the same gases.
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.
The concentration ranges can be redefined using the Range function
Manual screen, and the application gases can be redefined using the System
function, if they are not already defined as necessary.
CAUTION: Redefining applications or ranges might require
relinearization and/or recalibration.
To setup automatic ranging:
Enter the Range function to start the Range function.
: : : : :
If above screen displays MAN, use the UP/DOWN switch to Select
AUTO , and Enter.
Press Escape to return to the previous Analyze Function.
3.6.3 Precautions
The Model 6020 allows a great deal of flexibility in choosing ranges for
automatic range switching. However, there are some pitfalls that are to be
avoided.
Ranges that work well together are: