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4 Operation Model Ultra Trace 3000
4-20
Teledyne Analytical Instruments
Alarm Hysterisis: There is alarm hysterisis to prevent chatter of the
alarm contacts. It is set to 0.2 ppm for alarms set above 1 ppm,
and 10 ppb for alarms set below 1 ppm.
4.7 The
Range
Function
The Range function allows the operator to program up to three concen-
tration ranges to correlate with the DC analog outputs. If no ranges are
defined by the user, the instrument defaults to:
Low = 0–250 ppb
Med = 0–1 ppm
High = 0–10 ppm.
The Model Ultra Trace 3000 is set at the factory to default to
autoranging. In this mode, the microprocessor automatically responds to
concentration 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 90% 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 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 accurately with
full precision. See Front Panel description in Chapter 1.
The automatic fourth range is always 0-1000 ppm and is not program-
mable.
4.7.1 Setting the Analog Output Ranges
To set the ranges, enter the range function mode by pressing the
Range
button on the front panel.
L—250 ppb M—1 ppm
H—10 ppm Mode—AUTO
Use the < > arrow keys to blink the range to be set: low (L), medium
(M), or high (H).