A major problem that often comes up in industrial automation, particularly when trying to upgrade existing systems, is simply finding a way to get a process signal from point A to point B. Running physical wires between devices can be costly and time consuming, especially when there is a need to run them through conduit or dig trenches. Facilities that have been in operation for a long time may have gone through many iterations of process control equipment, leaving behind a rat's nest of old wires which make running of new wires nearly impossible. Certain applications can even prohibit the use of physical wires entirely, such as filling stations at shipping docks and truck terminals where the transmitter is located on the vessel or vehicle.
A fundamental principle of electricity is that current is the same at all points in a closed current loop. This is why the 4-20 mA current loop is the ideal analog standard for transmitting information over long distances, and through multiple meters, transmitters, data loggers, and other 4-20 mA loop devices. In this article you will learn what a loop-powered device is, what their characteristics are, and the advantages and weaknesses of using loop-powered devices. You will also get a better understanding of when to use, or not to use a loop-powered device.
A problem that often faces equipment installers in the process control industry, especially those installing into existing control systems, is the need to run additional power lines in order to provide electricity to all of the electronic devices. Not only does the sensor need power, but also the transmitter, valves, actuators, local display, and a number of other ancillary devices. The need for power is also often overlooked during the installation planning stages, leaving an equipment installer with devices installed and wired but unable to be powered.
Because of the prevalence of this problem, the ProVu series of digital panel meters, both AC and DC powered versions, include a 24 VDC power supply to drive the transmitter or sensor. This makes it much more convenient for installation. The ProVu power supply may also be used to power the 4-20 mA loop when used with a two-wire transmitter, eliminating the need for an external power supply. It's just one more reason why, no matter the application, ProVu has the solution.
The PD6600 Loop Leader is not just an ordinary process meter and display. This full-featured, loop-powered meter with its two open collectors and two solid state relays, is also capable of performing lead-lag pump alternation. For pumps used in applications such as tank level, pump alternation can be used to turn the pumps on and off to prevent excessive wear and tear. The PD6600 Loop Leader is unique because you can program pump alternation based on level and time. See all PD6600 Loop Leader models and features here.
Selecting the right enclosure for your meters is not an easy task. How many meters can I fit in the enclosure? What is the cutout size? How far apart do I space them out? All of these things can be daunting and time consuming to figure out. That's why Precision Digital created the Enclosure Selection Utility on predig.com. This easy 3-step process makes it quick and convenient for selecting the right enclosure and configuration for your meters. In addition to the Enclosure Selection Utility, you can go right to the panel meter's product page and look under the Enclosures and Accessories tab. There, you can click to see all compatible enclosures or use the configurator at the top of the page to narrow down your choices. Choose from a variety of different enclosures made from painted steel, stainless steel, or rugged thermoplastic. You can select up to 10 meters to be housed in our enclosures. The Enclosure Selection Utility is located at predig.com under the browse products menu or go to predig.com/esu.
Precision Digital's ProVu series of 1/8 DIN digital panel meters is our most popular product family. They offer a wide variety of analog and pulse inputs as well as Modbus® RTU serial communication, an easy-to-read dual-line display, UL/c-UL listing and CE marking, and a durable NEMA 4X front. All ProVu models are also available with optional SunBright® sunlight readable displays that can be viewed in direct sunlight. Watch the video here.
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