Pepperl+Fuchs Blog

I recently read "Creative Ways to Cut Costs in Hazardous Areas" by Dan Hebert, Senior Technical Editor at Control magazine. The article discusses some of the interesting applications where a hazardous-rated industrial HMI unit is required. Some of the solutions involve outdoor areas where they are exposed year round to high or low temperatures, rain, high winds, and bright sunlight. Other solutions involve long distances in between components and call for a way to communicate between these two points.


Because no two applications, solutions, or locations are exactly the same, the requirements of the end user can be drastically different. This means that manufacturers have to create standard products that cover the bulk of the applications, but also be flexible enough to create custom HMI solutions to cover the remaining applications that just cannot be satisfied by standard off-the-shelf solutions.

For more information on the industrial HMI products that Pepperl+Fuchs has to offer, please visit www.visunet.com. This website is our home base for all things HMI. It includes information on all of our standard and custom HMI solutions, as well as industry-specific information and a selection tool to assist in recommending a system that fits your exact application.

We recently launched our latest microsite, www.explosionprotection.com, which focuses on explosion protection solutions.

Your fieldbus technology questions answered...

What’s important to you and your operation? Is it a reduction in costs, easy maintenance, or simply just working within the confines of your aging infrastructure? If you answered yes to any of these questions, fieldbus technology might be something you should consider.

The answer is most certainly, “Yes!” But there are a few conditions that go along with using an IS barrier as a signal conditioner in a non-IS application.

At a plant or job site, Remote I/O installation processes happen in many phases. At times, certain equipment and bus communication lines may not be available from the early stages that would allow a user to configure and set up some of the controllers or Remote I/O modules.

First let’s define exactly what a fieldbus terminator is. A fieldbus terminator is a component of a fieldbus system that is the equivalent of a 1 µF capacitor and a 100 Ω resistor in series with each other. The main functions of fieldbus terminators are to shunt the fieldbus current and to protect the fieldbus signal against electrical reflections.

A match made for hazardous areas

A very common application we see working with intrinsic safety is one involving the use of a thermocouple. Pepperl+Fuchs has a wide variety of galvanically isolated intrinsic safety barriers that will work with these devices.

When in a hazardous location and working on selecting a barrier, the first question that needs to be answered is, “What type of signal(s) are you looking for on the control side of the barrier?” Once that question is answered, you can begin the process of selecting a barrier.

The first type of galvanically isolated barrier that we offer is a straight, low-voltage repeater: the KFD2-VR2-Ex1.50M. This barrier is powered by a 24 VDC supply and will simply repeat a 0 mV to ±50 mV signal from a thermocouple. There is no configuration required for this barrier.

The second option we have is our KFD2-UT2 series. These barriers will take a thermocouple input and convert the mV signal into a corresponding current or voltage signal, depending on the selection. The UT2 series of temperature converters is programmable via our free-to-download PACTware software and the use of an adapter cable (RS232 or USB options available) that must be purchased as an accessory. We offer these barriers in a few options:

KFD2-UT2-Ex1 --- Single channel, 4 mA … 20 mA output
KFD2-UT2-Ex1-1 --- Single channel, 1 V … 5 V output
KFD2-UT2-Ex2 --- Dual channel, 4 mA … 20 mA outputs
KFD2-UT2-Ex2-1 --- Dual channel, 1 V … 5 V outputs

The third option, the KFD0-TT-Ex1, is also classified as a thermocouple converter, which will take the mV signal input and convert it into a 4 mA ... 20 mA output. This specific barrier requires no outside software or programming cable to set up. All of the adjustments are made with DIP switches and fine adjustment potentiometers on the barrier.

The next barrier we offer is our KFD2-GU-Ex1 model. This barrier provides two Form C relay contacts that will be used as high- and low-temperature trip points that are user programmed. Once again, this barrier will require the use of PACTware and the adapter cable.

The last galvanically isolated barrier we offer for thermocouple applications is our KFD2-GUT-Ex1.D barrier. This is the most advanced barrier in the series and is basically a combination of the features on the “UT2” and “GU” barriers. It will provide two Form C relay contacts along with a 4 mA … 20 mA current output. The barrier can be programmed via a small keypad and LC display on the front or by using the PACTware software.

As with any of our K-System barriers, all of the above barriers have removable terminal blocks. As a separate accessory, we offer a terminal block that has built-in cold junction compensation for use specifically with thermocouples, the K-CJC-BU. This terminal block has an integrated encapsulated Pt100 RTD that is used for cold junction compensation, eliminating the need to maintain a known reference temperature.

Best choices for a Zone 1 application?

The KFD0-TR-Ex1 is an RTD converter

What you will want to do to fine tune this intrinsic safety barrier is as follows:

Look at these RTD Resistance Tables (PDF). The temperature value corresponds with the resistance values for the RTD.