Low pressure measurement gauges are specifically designed to accurately measure low-pressure levels, typically ranging from fractions of a psi (pounds per square inch) to a few psi. These gauges find application in various industries where precise measurement of low pressures is critical, such as in HVAC systems, pharmaceutical processes, leak detection, and vacuum systems. Here are some common types of low-pressure measurement gauges:

1. Bourdon Tube Gauges: Bourdon tube gauges can be adapted to measure low pressures by using a tube with a larger diameter and/or thinner walls. These gauges operate on the principle that a curved tube tends to straighten when pressure is applied. They are suitable for measuring pressures as low as a few tenths of a psi with good accuracy.

2. Diaphragm Gauges: Diaphragm gauges use a flexible diaphragm as the sensing element to measure low pressures. As pressure is applied, the diaphragm deflects, and this deflection is measured using mechanical linkages or strain gauges to determine the pressure. Diaphragm gauges can achieve high accuracy and resolution for low-pressure measurements.

3. Bellows Gauges: Bellows gauges operate similarly to diaphragm gauges but use a bellows-shaped sensing element instead of a flat diaphragm. Bellows gauges are suitable for measuring very low pressures, down to fractions of a psi or even vacuum pressures.

4. Capacitive Pressure Sensors: Capacitive pressure sensors measure pressure changes by detecting changes in capacitance between two conductive plates separated by a flexible diaphragm. These sensors can provide accurate and sensitive measurements of low pressures, often with digital output for direct interface with electronic systems.

5. Piezoresistive Pressure Sensors: Piezoresistive pressure sensors utilize the piezoresistive effect to measure pressure-induced changes in resistance. These sensors are highly sensitive and can be used for low-pressure measurements, especially when combined with appropriate signal conditioning and amplification circuitry.

6. Manometers: Manometers are simple devices used to measure low pressures by balancing the weight of a fluid column against the pressure being measured. U-tube manometers, well-type manometers, and inclined-tube manometers are commonly used for low-pressure measurements in laboratory and industrial settings.

7. Vacuum Gauges: Vacuum gauges are specialized instruments designed specifically for measuring pressures below atmospheric pressure. These gauges can accurately measure pressures in the millitorr or micron range, making them suitable for vacuum systems, semiconductor manufacturing, and other applications requiring precise vacuum control.

When selecting a low-pressure measurement gauge, it's essential to consider factors such as the desired pressure range, accuracy, resolution, response time, compatibility with the measured media, and environmental conditions. Additionally, calibration and periodic maintenance are crucial to ensuring the continued accuracy and reliability of low-pressure measurement systems.