A panel meter is an instrument that receives information from an input signal and then measures and displays that information in a digital or analog format. Usually mounted inside an instrument panel, it often indicates temperature, but may also reflect speed, pressure, current, and many other variables. The most common type of panel meter accepts a single input for display, although multiple channel devices are also available. Units are also available with large displays for visibility or in benchtop cases for portability. While analog panel meters used to be common, they have been replaced in most circumstances by the more accurate and functional digital meter.
An analog panel meter uses a moving needle and a dial to display information, and works on either the taut band or the jewel and pivot method. A taut band device uses a needle suspended between two ribbons of metal. Able to withstand high-shock, it generally measures direct current (DC). The less accurate pivot and jewel unit has a coil and pointer supported by polished steel, which fits into two jewel bearings. Better at withstanding vibration, it typically measures alternating current (AC).
An analog panel meter is more economical than its digital counterpart, but it's less accurate. Non-linear movement can produce errors, and the small meter screen can be difficult to interpret. It typically displays one value, however, so it's considered quicker to read. Analog meters are useful when relative change is more important than absolute accuracy.
A digital panel meter is used to measure and display all types of processes and electrical variables, from voltage monitoring to current, flow, speed, and more. It has a bright LED display that presents information in an alphanumerical format with little or no ambiguity. Many digital panel meters can accept multiple inputs and have adjustable or bar graph displays that allow users to easily switch between these inputs. Displays may also have totalizing, recording, conditioning, or other functional capabilities.
In addition to being significantly more accurate, a digital panel meter generally has more available features than an analog meter. It can be selected with alarm options, along with set point controls that allow users to establish control limits, as well as on/off controls that can activate or deactivate a process unit. Many digital panel meters can be connected to a computer to transfer data, and some have Ethernet capabilities that allow them to connect to a LAN or the internet.