How a Sonic Nozzle Gas Calibration Device Works

A Sonic Nozzle Gas Calibration Device is used to generate highly accurate and stable gas flow rates for calibrating flow meters. It operates based on the critical flow Venturi principle, where gas flow through a nozzle reaches sonic velocity (Mach 1) at the throat.

Working Principle of Sonic Nozzle Calibration

1️⃣ Gas Enters the Nozzle:

• The calibration gas (air, nitrogen, etc.) flows into the sonic nozzle from a pressurized source.

2️⃣ Choked Flow (Critical Flow Condition):

• As the gas passes through the converging nozzle, velocity increases until it reaches Mach 1 at the throat.
• Once the flow is sonic, it becomes independent of downstream pressure and depends only on upstream pressure and temperature.

3️⃣ Stable & Accurate Mass Flow:

• Since the flow rate depends on upstream conditions only, it provides repeatable and stable calibration gas flow.
• This eliminates fluctuations caused by pressure or flow disturbances.

4️⃣ Calibration of Flow Meters:

• The known gas flow is used to verify or adjust the readings of flow meters, such as thermal mass, Coriolis, or ultrasonic gas meters.
• Multiple nozzles may be used in parallel to cover a wide flow range.