Any installer of industrial process control equipment will tell you that ground loops are one of the most frustrating signal connection errors to diagnose and repair. The steps required in order to troubleshoot them are often equated to something as mysterious as magical incantations. Issues caused by shared, non-isolated commons are viewed with a similar outlook. Difficulties with shared signal returns are often even confused with ground loops. Ground loops and shared commons can both cause unpredictable signals and render your current loop unusable. The best and most practical way to repair these signal issues is to prevent them from occurring in the first place by planning proper device wiring and following specific best practices. However, if you suspect that you are having signal issues related to ground loops or shared commons in an existing network, no need to pull out the spell Ground Loops & Non-Isolated Commons book and magic wand, there are some predictable symptoms which you can look for in order to diagnose the problem.
The previous article in this series discussed loop-powered, or two-wire, devices. These instruments utilize the power supplied to the current loop to power themselves. A two-wire connection may not always be the most optimal power solution because of its inability to power devices that require a large voltage drop. Three and four-wire devices incorporate an external power supply in order to effectively eliminate the voltage drop placed on the process signal current loop. It is important to understand the differences between these three setups as they are fundamentally different and each has its own advantages as well as limitations. This article will define what a two, three, and four-wire connection is, discuss what the pros and cons are, and provide you with the necessary information for choosing the right wiring for your application.
Our first Tech Tips video shows the 24 VDC @ 200 mA power supply offered with the line-powered ProVu Series of digital panel meters. This power supply is most commonly used to power the two-wire 4-20 mA transmitter for which the meter is displaying the process variable. The video explains the power supply option and shows how to wire the meter to the transmitter for this application. Watch it here.
We plan to release more of these videos in the future and would like to know what you think. Do you think these videos will be helpful? Do you have any ideas for future videos? Please contact our marketing department with any feedback you may have!
Early this month, Precision Digital invited a group of distributors to take part in a 2-day sales training seminar held at its headquarters in Hopkinton, MA. Salespeople from over a dozen companies nationwide engaged in interactive presentations and hands-on workshops. The participants learned everything from the value of showing a demo unit to assembling a ProVu process meter and hooking it up to one of their own transmitters, as well as programming the meter for a specific application. The attendees also had opportunities to converse with many of Precision Digital's product, sales, and engineering experts. After the first full day of activities, the participants got to wind down and enjoy a Boston Red Sox game at Fenway Park that evening. In the end, the attendees walked away with a better understanding of Precision Digital products, how to sell PDC, and how to make more money on every sales call. See photos from the event.
Precision Digital now offers Spanish language versions of the ProVu PD6000 process meter and Trident PD765 process & temperature meter datasheets. These datasheets can be conveniently downloaded from predig.com. You will find a link to the datasheet on the product page under the docs & resources tab, or click the documentation link at the top of the home page and enter the model number in the search field. Start seaching for datasheets here.
Our new Tech Tips series of videos quickly explain a specific feature that our products offer and how it can be used to meet the needs of your application. This video walks you through the process of connecting a 2-wire transmitter to a Precision Digital ProVu series meter. Watch the video here.
- Helios CE, UL and C-UL approval coming in next month or two
- What's new on predig.com website
- New Loop Leader loop powered panel meters receive ATEX and IECEx approval: Available mid-November. UL approval underway