Pressure detection devices can be classified on the basis of the pressure ranges they can measure, on the basis of the design principle involved in their operation, or on the basis of their application. In this chapter, the various categories are not separated in any strict manner. Industrial instruments are discussed in detail, with emphasis on the most commonly used devices; laboratory instruments are covered in less detail.Silicon microchip technology continues steadily to reduce the cost of advanced features, reducing the size and weight of hardware and improving their availability and accuracy, while extending the long-term stability their calibration. Many of the sensors are available with digital communication capability, which can serve calibration, adjustment, and reporting of process variables, allowing for complete plantwide integration. With so many types of sensors, it might seem that making the proper selection for a particular installation would be difficult and time consuming. Actually, this is not the case. A multitude of devices are covered here for the purpose of completeness, but for a typical industrial installation, the selection is fairly simple, and often repetitive.Each section starts with a brief summary of basic features applicable to the group of instruments discussed in that section. This information allows readers to quickly determine whether that category of instrumentation is suitable for their application. This chapter covers a wide range of pressure sensors, which can measure pressures from ultrahigh vacuums, such as 10 - 13 mmHg, to ultrahigh gauge pressures approaching 400,000 PSIG (2,800 MPa). The range of the costs and inaccuracies of these instruments are equally broad. A simple, 1.5 in. diameter, 5% inaccurate gauge might cost only $10, while a fused-quartz helix sensor with an error of 0.01% and a digital readout could cost $6000. The cost of pressure transmitters range from a few hundred dollars or less for the disposable models that have limited features, to $2000 for smart models with built-in digital PID control algorithms and/or digital networking capabilities.Reliable reference