Teledyne 3020T operating instructions Range Function, Setting the Analog Output Ranges

4 Operation Model 3020T

–OR –

Go to Ltch– and then assert either DOWN two times or UP two times. (Toggle it to N and back to 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).

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