4 Operation
Model 2000A-EU
4-20
Teledyne Analytical Instruments
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:
Press
Range
key to start the Range function.
Select range mode
Range mode : AUTO
Note: If all three ranges are currently defined for different applica-
tion gases, then the above screen does not display (because
mode must be manual). Instead, the VFD goes directly to the
following screen.
If above screen displays, use the
∆∇
arrow keys to Select
AUTO
, and
press
Enter.
Select auto ranging
Gas use: O2 N2
Use the
∆∇
arrow keys to change the application (gas use:).
Press
Escape
to return to the previous screen to select or define another
range.
Press
Enter
to return the to the
Analyze
function.
4.6.3 Precautions
The Model 2000 allows a great deal of flexibility in choosing ranges for
automatic range switching. However, there are some pitfalls that are to be
avoided.