Digital Panel Meters
Digital panel meters are multifunctional measuring devices, widely used in industrial applications, that monitor and display the essential parameters that make processes go—like voltage, current, frequency, and various process signals themselves. They are accurate, reliable, and easy to read, and they can be found in applications ranging from the "high end" (where they appear as part of precision control and monitoring systems) to the "low end" (where they show up in simple but potent combinations with various types of sensors and switches).
Providing both analog and digital inputs, digital panel meters offer flexible data acquisition and often come with alarm triggers, set points, and relay outputs. The latter make for safe and reliable industrial control environments (i.e., no high voltages and consequently no high currents to worry about in the hazardous part of the control circuit if a relay contacts fail). The meters also communicate well with other devices you might have on hand for centralized monitoring of the situation, or at least for clever data logging. Serial communications—RS-232, RS-485, etc.—are not a problem for these units.
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More Information about Digital Panel Meters
Digital panel meters are extremely flexible. They can be powered by various power sources, including DC power and low-voltage configurations, and they can be outfitted with special input modules for a load cell, strain gauge, or thermocouple—in other words, for any number of undertakings that demand very precise measurements and high performance.
Digital panel meters can display flow rate for pump control applications and often come with front panel pushbuttons. Their analog inputs allow them to read varying signals from sensors or other devices, while their analog outputs enable them to transmit scaled analog signals to other equipment for control or monitoring purposes.
HMI vs OIT, What's the Difference
Human Machine Interface (HMI) is a software interface that allows operators to interact with various pieces of electrical hardware and controls systems. HMI typically utilizes monitors or screens to display information, which are referred to as HMI screens. The screens are not the actual HMI, but are a tool used to display HMI software. For example, electrical enclosures often have screens mounted on the outside of them to provide users with information about ongoing process and to allow users to make changes to the system.
Operator Interface Terminal (OIT) typically displays basic information about the electrical hardware that it is attached to. It provides only local information about the environment it is interfacing with and allows control and monitoring for that one piece of hardware, not an entire system.