Teledyne 3000TA-EU - General purpose trace oxygen analyzer - Manual (Page 64)

Operation 3000TA- EU
Teledyne Analytical Instruments
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The Model 3000TA is set at the factory to default to autoranging.
In this mode, the microprocessor automatically responds to concen-
tration changes by switching ranges for optimum readout sensitivity. If
the current range limits are exceeded, the instrument will automatically
shift to the next higher range. If the concentration falls to below 85% of
full scale of the next lower range, the instrument will switch to that
range. A corresponding shift in the DC percent-of-range 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 oxygen concentration detected. If
the concentration exceeds the upper limit of the range, the DC output
will saturate at 1 VDC (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
accurately with full precision. See Front Panel description in Chapter 1.
The automatic air calibration range is always 0-25 % and is not pro-
grammable.
4.6.1 Setting the Analog Output Ranges
To set the ranges, enter the range function mode by pressing the
Range button on the front panel.
L—100 M—1000
H—1 0000 Mode—AUTO
Use the ◄►arrow keys to blink the range to be set: low (L),
medium (M), or high (H).
Use the ▲/▼ arrow keys to enter the upper value of the range (all
ranges begin at 0 ppm). Repeat for each range you want to set. Press
Enter
to accept the values and return to Analyze mode. (See note
below.)
Note: The ranges must be increasing from low to high, for
example, if range 1 is set as 0–100 ppm and range 2 is set
as 0–1,000 ppm, range 3 cannot be set as 0– 500 ppm
since it is lower than range 2.
Ranges, alarms, and spans are always set in ppm units (over the
entire 0-250,000 ppm range), even though all concentration-data outputs