There are many types of instruments used to measure absolute or gauge pressure. Pressure measurement devices can be separated into two categories: mechanical and electronic.
Level measurement devices can detect, indicate, and/or help control liquid or solid levels. Level measurement devices can be separated into two categories: direct, or mechanical, measurement and electronic measurement.
Spectrometers use light wavelengths to investigate the chemical composition of a sample. Atomic spectrometers use an analytical method by which one or several elements in unknown mixtures can be detected.
Humidity is a measure of the amount of water vapor in the air. It is generally reported as relative humidity, absolute humidity, or dew point temperature.
Gas and flame detectors determine the presence of a gas or fire, respectively. Gas monitors check or regulate the amount of gas present. The gas detectors pictured below detect carbon monoxide and hydrogen sulfide.