Hach 3650 ATEX manual Barometric Pressure Sensor, GAS Sensor, A Span Gas Calibration

Calibration

BAROMETRIC PRESSURE SENSOR

The instrument internal barometric pressure sensor is calibrated at the factory, and normally requires no further attention. However, you may wish to calibrate it against your own instrumentation, or simply check the instrument for accuracy.

Select Troubleshooting, Pressure Calibration from the WinLog97 program, and enter the current atmospheric pressure, in mbars, in the calibration pressure entry box.

GAS SENSOR

The sensor can be calibrated either in air or directly in line in a liquid sample. Additionally, oxygen sensors can be calibrated using a span gas.

To perform a calibration, you must first choose which method you wish to use. The mode of calibration may be selected using the WinLog97 program. Alternatively, you can select the mode of calibration using the instrument front panel buttons.

Switch the instrument power OFF. Switch the instrument on by holding down the CAL button, and then pressing the POWER button at the same time. The instrument display will show either Air for in air calibration, LI for in line calibration, or SPA for span gas calibration

Use the × Ø buttons to change the mode to your choice and press the STO button to set the selected mode.

In a Span Gas Calibration

The span gas calibration procedure may be used if you have a source of gas with a known concentration of O2 (in% units). To perform this

type of calibration, the instrument must be set for calibration In a Span Gas. The Windows WinLog97 program must also be used in this procedure.

Switch on the instrument, if necessary, and wait a minute or so for the displayed measurement to settle. Then expose the sensor to a span gas sample with a known oxygen concentration . Enter the percentage of oxygen in the span gas using the WinLog97 program.

Press the CAL button . Remember, this button may have been locked out to prevent an accidental reset.

Abrief clearing [---]message appears. Press CAL again within a 3 second period. The percentage of the measured current to the ideal one is

displayed.

When the reading is stable, press CAL again.

If the new calibration current is within 25% to 175% of the ideal current, the instrument displays CAL and returns to the measurement mode. Calibration is now complete, the sensor is calibrated, and you can proceed with your measurements.

If the new calibration current is not within this range, the instrument displays Err and returns to measurement mode. The system will not calibrate, and it is likely that a sensor service will be required.

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