Understanding Vacuum Gauge Types Classifications and Their Measurement

A vacuum gauge is an instrument for measuring the pressure of gases or vapours below atmospheric pressure. Absolute vacuum gauges calculate pressure directly from a measured physical quantity, whereas relative vacuum gauges require calibration against an absolute standard.

The relationship between a physical phenomenon and pressure is most pronounced within a specific range, known as the gauge's "measurement range." Covering approximately 19 orders of magnitude (from 10⁵ down to 10⁻¹⁴ Pa) requires multiple gauge types, each optimized for a specific region. This necessity can lead to measurement uncertainties at the overlapping boundaries between different technologies. The key to performance improvement lies in enhancing the primary measurement effect while suppressing parasitic signals.

The following table summarizes the typical pressure ranges for common vacuum gauges:

Vacuum Gauge Types

Vacuum Gauge Name	Measurable Pressure Range (Pa)
U-tube Manometer (Mercury)	10⁵ – 10²
U-tube Manometer (Oil)	10⁵ – 10²
McLeod Gauge	10³ – 10⁻³
Diaphragm Gauge (Mechanical)	10⁵ – 10²
Diaphragm Gauge (Electronic)	10⁵ – 10⁻³
Thermal Conductivity Gauges
Pirani Gauge	10⁴ – 10⁻²
Thermocouple Gauge	10² – 10⁻¹
Thermistor Gauge	10² – 10⁻¹
Ionization Gauges
Hot Cathode (Triode)	10⁻¹ – 10⁻⁵
Bayard-Alpert (B-A) Type	10⁻² – 10⁻⁸
Hot Cathode Magnetron	10⁻⁵ – 10⁻¹⁰
Cold Cathode Gauge	1 – 10⁻⁵
Momentum Transfer Gauges
Viscosity Gauge	1 – 10⁻⁵
Knudsen Gauge	10⁻¹ – 10⁻⁵

Selection Guidance: For higher pressures (10⁵ – 1 Pa), mechanical gauges like U-tube manometers or diaphragm gauges are suitable. The middle vacuum range (10³ – 10⁻² Pa) is often covered by thermal conductivity gauges (Pirani, thermocouple). For high and ultra-high vacuum (below 10⁻¹ Pa), various ionization gauges become essential. Understanding the operating principle and limitations of each type is crucial for selecting the right tool for a specific application and ensuring accurate pressure readings.

Disclaimer: This article provides a general overview of vacuum gauge classifications and typical measurement ranges for informational purposes. Specifications may vary by manufacturer and model. It is not intended as professional engineering or scientific advice. For critical applications, always consult the manufacturer's documentation, relevant standards, and qualified technical personnel.

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