Subscribe via E-mail

Your email:

Follow Me

Pepperl+Fuchs USA Blog

Current Articles | RSS Feed RSS Feed

Protect your Industrial Cables and Cable Connectors!

Protect your industrial cables!

Pepperl+Fuchs' standard 22 AWG cordsets are rated for 4 A. But most main enclosures have a power supply that is much larger than the rating of individual industrial cables and devices.

So, what if there's a situation where an output overloads, pulling 10 A or 20 A through a 4 A rated cable? The wires will start to heat up, the voltage will drop, and the cable connectors may get damaged. The worst case scenario could be a fire.

To protect the end devices, fuses or breakers are used to open the circuit in the event of cable or device failure. To do it right, you really have to fuse every sensor or fuse groups of sensors so the current limit to the cables is below the 4 A limit.

Overload or short-circuit protection must also be considered with industrial bus systems. AS-Interface is an industrial bus that provides power and communication to modules on the network. This network is designed to be completely field mountable so the use of fuses or breakers for every bus drop may not be convenient. If a power supply that is rated 4 A or less is used to power the entire bus, then no problems exist. The drop cables can’t be overloaded because the power supply can’t provide that much current.

Alternatively, what if you use an 8 A AS-Interface power supply and a 12 A auxiliary power supply? We have an auxiliary power cable with larger 13 AWG conductors that are rated for 12 A. It is possible for the drop cables off the AS-Interface trunk to be overloaded. What to do? You can’t put fuses in all the drop lines; there's nowhere to put them. And the fuse itself may interfere with AS-Interface communication. You could just mount everything to the trunk line so no drop cables are used at all, but that isn’t convenient or practical.

A simple solution comes with our series of PTC-protected drop connectors.
The idea is to limit the current that is delivered to the drop in order to protect the cable. With these cable connectors, the current is limited to 1.6 A, which is far below the 4 A cable limit. Once the short is removed or the end device is repaired, the drop cable will function normally and your network will come back up and run. LED indication on these protective devices will tell you where the short is so the problem can be easily resolved.

These drops are IP69K, washdown rated for use in the harshest conditions, and feature a 1 m pigtail with a straight M12 connector. They are available in an AS-Interface version and an AS-Interface/auxiliary version. Depending on quantity, we can provide additional versions with different connector styles and drop cable lengths.

This Valve Position Sensor Is Rugged and Outdoorsy

Valve sensor for outdoor use

Most valve position sensors on the market today are designed for process valve automation applications and environments where limit switch boxes with mechanical, magnetic, or inductive contacts are typically used to detect the position of the valve in valve actuators.

Industrial Sensors: Differences between No-load Supply Current and Load Current

Industrial Sensors and current consumption

The current consumption of an industrial sensor is a very important consideration. Knowing the current consumption of all your devices on a machine allows you to size wire properly and pick the right power supply for the application.

Moving from Wired HART Communication to WirelessHART

HART Communication

In a previous blog post, "General Characteristics of HART Communication", I went over the important aspects of HART, which is a wired communication technology that has been in existence since the 1980s. Naturally, technology does progress, and just like telephones moving from land lines to wireless, wired HART is moving to WirelessHART. Let's explore what you should know about WirelessHART, and what improvements it can offer to your plant communication.


Photoelectric Sensors Are at Home on the Automotive Factory Floor

Photoelectric sensors for automotive assembly

I recently had the opportunity to tour the body shop of an automotive assembly plant. Working for a company that makes sensors for this industry, I was looking forward to seeing our "heavy-duty, weld-slag resistant sensors with magnetic-field immune electronics that stand up to the rigors of the robotic welding cell."

6 Steps to Selecting a Fiber Optic Cable

6 Steps to Selecting Fiber Optic Cables

When selecting a fiber-optic cable, it is not as simple as “What fiber cable goes with this sensor?”  There are multiple factors that contribute to selecting the appropriate fiber-optic cable for your application. 

Why the Incredible G10 Housing is an AS-Interface Game Changer

G10 Module is a Game Changer for AS-Interface

AS-Interface is all about simplifying the designs of a control system, reducing the complexity of the wiring,cutting the cost of the installation, improving diagnostics, and making automation more productive.


General Characteristics of HART Communication

HART communication uses the BELL 202 telephone communication standard

Highway Addressable Remote Transducer

HART is a digital signal that rides on a standard 4 mA ... 20 mA process control loop. In the field of process automation, the 4 mA ... 20 mA loop is very steady. You may hear of it being referred to as “quasi-static,” as it doesn't change much. Field devices like mass flow, temperature, pressure transmitters, or valve positioners use this 4 mA ... 20 mA signal. HART information is extra information that you get back from your field instruments.
Historically, HART communication uses the BELL 202 telephone communication standard, which telephone land lines still use today. This standard was introduced in the early 1980s and uses Frequency Shift Keying (FSK) technology. FSK simply means that the information is keyed or coded into the frequency, which is how the data communicates back and forth. HART layers its digital communication signals on top of the 4 mA ... 20 mA control signal.

A drawback based on today's standards is the speed of HART communication, which is rather slow. HART is limited to 1200 bits/second and ranges from 1200 Hz to 2200 Hz. Information (1, 0) is represented by different frequencies. The HART signal creates 0s and 1s. A logic 1 is represented by 1200 Hz. A logic 0 is represented by 2200 Hz. On the plus side, HART communication doesn't interrupt the 4 mA ... 20 mA signal, and it allows a host application (master) to get up to three digital updates per second from a field device.

Back in the day when this technology was introduced, 1200 baud was screaming fast, but now it is painfully slow and just doesn't measure up to our expectations. As an example, a LAN (Local Area Network), in common use today, perks along at 100 Mbits/second. That's 1000 times faster than the BELL 202!

If the communication speeds are so slow, why do we continue to use HART communication for field instruments and devices? Well, the 4 mA ... 20 mA control signals with FSK are reliable and have been in use for decades. There is a large installed base of devices. By our estimates, there are at least 30 million HART-compatible field devices in use worldwide.  

Also, the HART information is easily extracted without interfering with the 4 mA … 20 mA signal used by the host system. Host systems are most commonly a distributed control system (DCS), programmable logic controller (PLC), asset management system, safety system, or a handheld device. HART enables two-way field communication to take place and makes it possible for additional information beyond the normal process variable to be communicated to or from a smart field instrument.

Interested in learning more about HART communication and solutions? Download our brochure:


What in the World are Cyber-Physical Systems?

What are cyber physical systems?

If you scan the Internet for the term Cyber-Physical Systems (or CPS) you will find many contributions discussing topics from mobile phones to time-aware software. CPS are objects that bring the physical (i.e., hardware) together with the computational world. In that sense, a modern car is an application of a CPS.

Tags: ,

Sensing Clear Objects with Photoelectric Sensors

Using Sensors to See Clear Objects

Sensing or counting clear objects using a standard photoelectric sensor can be difficult.  That’s because standard photoelectric sensors are not sensitive enough to detect the small attenuations in light that clear objects cause.  To accurately sense glass or plastic bottles, clear packaging, or even transparent films, Pepperl+Fuchs offers special wide-beam diffuse sensors and also advanced retroreflective models, designed specifically for sensing clear objects.

All Posts