Pepperl+Fuchs USA Blog

What is PCV?

PCV is an absolute linear positioning system.  A continuous band of Data Matrix codes is installed along the application’s travel path. A camera-based read head, typically mounted on the moving part, reads these codes.  Depending on the type of read head, position data is transmitted to the control system using RS485, SSI, or PROFIBUS DP communication.

In certain applications with spinning components, keeping track of the speed or revolutions per minute is vital for controlling equipment and processes. Pepperl+Fuchs offers several solutions to achieve this.

During the years I have worked at Pepperl+Fuchs, I have been asked a lot of questions regarding the implementation of intrinsic safety, or IS for short. As they say, “Knowing is half the battle,” so I decided to share a few of those questions and answers. 

Fork-type. U-shaped. Slotted. Vane-style. Slot housing. Whatever you call it, the housing is distinct among all other photoelectric sensor housings. And just as a fork is better suited for certain eating tasks than a spoon or knife, the fork sensor, or as it is more commonly called, the slot sensor, is a utensil that has its own strengths.

Different sensor connection types

Electronic sensors require connection in order to receive their power and transmit their output.  A connection diagram, included on the sensor’s datasheet and often printed on the device if room allows, labels each available connection point. 

The MNI40 magnetic incremental rotary encoder is the most compact encoder in the Pepperl+Fuchs product line.  Even with its small size, this incremental encoder is extremely durable and is not affected by environmental conditions. It has an IP67 protection rating, so you can expect reliable performance in dirty, dusty, or even wet conditions.  It also has a large temperature range from -40 °C to 100 °C and has proven itself with a long service life at these extreme temperatures as well as operating at high speeds.

Years ago it was easy. Cars were made out of steel, inductive sensors sensed the presence of steel, case closed. Today there are several alternative materials used in the manufacturing of vehicles above and beyond steel. Today’s vehicles are made out of different materials such as aluminum, plastic, and fiberglass.

Measurement displacement sensors are used when you need to know a continuous distance that the sensor is from a selected target. There are two primary output types that can give distance.

...or any long cable run

Voltage drop is something to think about before installing any industrial network that uses power and communication on the same two conductors.  These networks include AS-Interface, PROFIBUS PA, and FOUNDATION fieldbus.  For that matter, voltage drop should be considered anytime a device is located at the end of a long cable run.

Mention the word NAMUR to a valve specialist and the first thing this person will think about are the interfaces used to connect solenoids to actuators and switch boxes or positioners to rotary pneumatic actuators.Mention NAMUR to a controls person and the first thing that will come to mind are intrinsic safety techniques.

Both are correct. A typical automated valve assembly for on/off service consists of a valve (rotary or linear travel), an actuator, position sensors, and a solenoid.  An automated valve for control service adds a valve positioner but subtracts the solenoid.  

The selection of the components needed in the assembly is dependent upon the service application and the area (environment) where the assembly will be installed.

Such areas, known in the process industry as Divisions or Zones, may be simplified to three categories:

• Nonhazardous
• Occasionally hazardous
• Continuously hazardous

Electrical devices used in hazardous areas must not be capable of initiating an explosion or else be encased in an approved heavy-walled enclosure that will contain an explosion should one be caused. A device that is intrinsically safe cannot create an explosion; therefore, it prevents an explosion from occurring.

Prevention is always the preferred choice over containment when selecting hazardous location devices.  

A NAMUR-compliant sensor is intrinsically safe, prevents an explosion from occurring, and can operate continuously in a hazardous location.

A NAMUR sensor is paired with a barrier that limits the electrical energy available to the sensor to non-ignition levels. The barrier provides enough power for the sensor to properly operate but not enough to cause ignition via heat generation or by the creation of a spark above safe threshold levels. When the sensor detects the valve position, the barrier amplifies the output signal and then initiates either a relay closure or an electronic signal. This output is typically fed into a PLC or similar control/supervisory system.

By using NAMUR sensors to detect valve position for process valves in hazardous locations you benefit in two ways—proven explosion prevention and the elimination of a costly unnecessary enclosure.