Teledyne 3020T - Manual (Page 52)

4 Operation Model 3020T
4-16 Teledyne Analytical Instruments
–OR –
Go to
Ltch– and then assert either DOWN two times or UP two
times. (Toggle it to
N NN N N and back to Y. Y. Y. Y. Y.)
4.10 The RANGE Function
The RANGE function allows the operator to program up to three
concentration ranges to correlate with the DC analog outputs. If no ranges
are defined by the user, the instrument defaults to:
Low = 0–100 ppm
Med = 0–1,000 ppm
High = 0–10,000 ppm.
The Model 3020T 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 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 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 air calibration range is always 0-25 % and is not pro-
grammable.
4.10.1 Setting the Analog Output Ranges
To set the ranges, ENTER the RANGE function mode by selecting
RANGE from the MAIN MENU. The RANGE screen appears.
L—100 M—1000
H—10000 Mode—AUTO
Use the DOWN/UP control to the range to be set: low (
L), medium (M),
or high (
H).