Sensor Calibration

BEFORE YOU BEGIN:

Never perform a span calibration without first performing a zero calibration.

The Zero calibration should be performed with a gas that contains no hydrogen (0% H2). Common gases used include nitrogen, argon, or ammonia. The concentration of the Span calibration gas should closely resemble the gas that is being measured. The span gas should contain a minimum %H2 that the sensor could be exposed to during normal operations. For example, if the sensor might see up to 75% H2, the span gas should contain at least 75% H2 in its chemistry.

NOTE: Since the accuracy of the calibration gas directly influences the resulting accuracy of the instrument, the highest possible accuracy grade should be obtained. Some gas suppliers refer to this as a “Certified Primary Standard”. The high degree of accuracy is not required to obtain nominal values that exactly match the values shown above. The accuracy is required to know the exact composition of the gas in the cylinder. The actual composition will be shown on the bottle when it is delivered.

When flowing calibration gas into the analyzer, turn the pump off. The amount of flow from the gas cylinder should be approximately 1.5 cfh at no pressure. The gas cylinders will be under high pressure, so it is recommended that a two stage regulator with a low pressure secondary stage be used. It is good practice to begin the flow of gas before attaching the calibration gas to the instrument. This will prevent any high pressure bursts from entering the instrument.

Calibration gases can be obtained from Super Systems, however they can also be obtained from any supplier of custom gases.

Zero Calibration Procedure

1. Connect the zero gas to the “Calibration Gas Inlet” port on the side of the enclosure. It is recommended to let everything (gas and enclosure) sit for approximately thirty minutes to allow the temperature to achieve equilibrium.

2. Turn the ball valve to the “Calibration Gas” so that calibration gas can flow through the sensor.

3. Select “Sensor Calibration” from the Main Menu.

4. Select “Zero Hydrogen.”

5. Tap the value shown next to the “Enter supplied target value:.” This will display a keypad to enter the zero gas hydrogen percentage.

6. Enter the appropriate concentration of the calibration gas (in this case 0% since it is a zero calibration).

7. Begin the flow of gas and wait until the gas reading on the display stabilizes. This occurs when the actual values are not moving in a specific direction, and they display only slight movements up and down. This may take up to several minutes.

8. Once stabilized, press the “Calibrate” button.

9. The gas value will adjust immediately to match the calibration gas concentration entered in Step 5.

After the Zero Calibration is complete, turn off the flow of gas and disconnect it from the enclosure.

Span Calibration Procedure

1. Connect the span gas to the “Calibration Gas Inlet” port on the side of the enclosure. It is recommended to let everything (gas and enclosure) sit for approximately thirty minutes to allow the temperature to achieve equilibrium.

2. Turn the selector valve to the “Cal Gas Inlet” so that calibration gas can flow through the sensor.

3. Select “Sensor Calibration” from the Main Menu.

4. Select “Span Hydrogen.”

5. Tap the value shown next to the “Enter supplied target value:.” This will display a keypad to enter the span gas hydrogen percentage.

6. Enter the appropriate concentration of the calibration gas (the %H2 should be at least the maximum amount of hydrogen typically measured in operation).

8. Once stabilized, press the “Calibrate” button.

9. The current gas value will adjust to match the calibration gas concentration immediately.

After the Span Calibration is complete, turn off the flow of calibration gas, turn the ball valve back to ‘Sample Gas,’ and disconnect the calibration gas from the enclosure.