In ambient air monitoring and other applications, when using gas analyzers and gas dilution calibrators, the Alicat Whisper series of portable gas flow meters can reduce flow calibration time.

1.Detection gas analyzer and gas dilution calibrator

Calibrating the gas analyzer will consume you a whole day. The scariest thing is the low flow calibration, which may take an hour or two.

The bubble or piston slowly rises to the top of the positive displacement tube at a speed of 10 cm within a few minutes. For a single average data point, repeat it 9 times, which is a good way.

A gas analyzer and a pair of gas dilution calibrators in a typical ambient air monitoring shed. The lower left is the Alicat Whisper series mass flow controller.

Every technician knows that maintaining a constant sample gas flow is essential to ensure the measurement accuracy of the gas analyzer.

The gas analyzer is used for ambient air monitoring to determine the concentration of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the air. Process analyzers are used to monitor the concentration of these gases in the stack emissions.

Unfortunately, the built-in mass flow controllers of these analyzers often do not meet our expectations, which requires regular flow checks and calibrations to ensure data reliability.

The flow of the analyzer can be calibrated directly with a high-precision flow meter. When testing the composition of a gas analyzer, use a gas dilution calibrator, which uses two or three mass flow controllers to control the composition of its outlet gas flow.

The gas dilution calibrator combines a large flow of uncontaminated air with a small flow of the analyzed greenhouse gas to provide a polluted gas sample of the required concentration. The mass flow controllers in these gas dilution calibrators use high-precision flow meters to ensure their correct operation.

2 Faster flow calibration and laminar flow pressure difference

The calibration of the mass flow controllers of gas analyzers and gas dilution calibrators usually uses positive displacement flow meters for measurement.

“Wet” volumetric flow meters measure the time it takes for air bubbles to pass through a pipe coated with soap solution. The “dry” positive displacement flow meter measures the time it takes for the air to push the piston up.

In both cases, a single flow measurement data point may only take a few seconds to a few minutes to complete, depending on the flow rate.

Using these slow measurement methods, calibrating all the analytical instruments in the ambient air monitoring shed can easily take a whole day.

MW series low pressure loss gas mass flowmeter

The Alicat Whisper series (MW series low pressure loss gas mass flow meters and MWB series portable low pressure loss gas mass flow meters) measure extremely low pressure differences through laminar flow elements, and display the actual volume flow and standard mass flow in real time.

The flow reading is calculated a thousand times per second (1000 Hz), so even very low flow rates can be seen immediately.

Streaming through RS-232 and recording these data can reveal inconsistencies in the circulating flow and help identify poorly performing mass flow controllers.

The wide flow range of the Alicat NIST traceable mass flow meter (200:1, or 0.5% to 100% of full scale) means you can calibrate the gas analyzer mass flow controller to the bottom of its range to ensure the accuracy of calibration .

The Whisper series of mass flow meters are available with universal mass flow controllers of 20 slpm, 10 slpm, 200 sccm, 100 sccm and 5 sccm, or any other range between 0.5 sccm and 1000 slpm.

These flow meters are also suitable for other applications, including:

Review the flow rate of indoor air sampling instruments used in industrial hygiene applications

Setting up the mass flow controller used with the air sampling tank

Calibration of mass flow controllers used in gas chromatographs and other analytical instruments

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