Analog panel meters are instruments that measure variables such as pressure, flow, temperature, speed, current, and voltage. They display values on a dial, usually with a moving pointer or needle. Many types of analog panel meters are available. The most common type accepts a single input from a temperature sensor such as a thermocouple or resistive temperature device (RTD). Analog panel meters can also accept pulses, frequencies and signals. Multiple channel devices are available. With the advent of digital technology, analog panel meters are used less frequently; however, some applications still require them. For example, analog panel meters are well suited for applications that require users to scan many devices to determine whether an individual meter is incorrect. For improved usability, analog panel meters with anti-glare, mirrored, and illuminated faces are available.
Selecting Analog Panel Meters
Selecting analog panel meters requires an understanding of meter mechanisms. Two basic methods are available: taut band and pivot and jewel. Taut band suspends a moving pointer or needle between two ribbons of metal to reduce friction and increase meter sensitivity. Taut band devices can withstand varying amounts of shock and are suitable for high vibration environments. Pivot and jewel analog panel meters can also withstand high amounts of vibration, but do not match the accuracy and repeatability of taut band devices. With pivot and jewel analog panel meters, a coil and pointer are suspended by polished steel and fit into two jewel bearings. Typically, pivot and jewel devices are used to measure alternating current (AC). By contrast, taut band devices are often used to measure direct current (DC).
Analog panel meters are available with one or more channels and can measure one or more variables in different units. For example, some devices only measure DC in volts while others measure AC in volts or millivolts. Analog panel meters can also measure single or three phase power. Devices that measure radio frequency (RF) signals are also available. Most analog panel meters feature a range of measurements such as 0 – 4 mA or 0 – 10 VDC.
Important specifications for analog panel meters include face type, depth behind panel, and dimensions. Round, rectangular, and standard face types are available. Rectangular devices vary in terms of front face height and front face width. Round devices vary by front face diameter. Standard devices have a barrel or panel cutout diameter. Other specifications for analog panel meters include scale length, response time, and reference point. For devices that use zero as a reference point, scaling methods include zero-left, zero-right, and zero-center. Analog panel meters can also start from a non-zero value.
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Digital Panel Meters
Digital panel meters measure and display processes and electrical variables via an alphanumeric digital readout.