Product category:
Level Sensors and Leak Detectors
News Release from: Rechner UK | Subject: PER level probes
Edited by the Engineeringtalk Editorial
Team on 31 January 2003
Level probes avoid common capacitive
problems
Rechner level probes are unique in the way that they work and are now available with evaluation units integral in the head of the level probe.
Rechner level probes are unique in the way that they work and are now available with evaluation units integral in the head of the level probe The upper part of the connection head with cable exit (Pg9 screwing) can be rotated through 340 degrees, ensuring that the cable exit can be in the desired position
This article was originally published on Engineeringtalk on 31 Jan 2003 at 8.00am (UK)
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Proximity sensors come with ATEX certification
Rechner's range of capacitive proximity sensors already includes devices certified StEx "for use in explosion danger areas with combustible dust", and these are now available with ATEX certification.
Capacitive sensors safe for dusty environments
Rechner Sensors has a range of new capacitive sensors that are compliant with the new ATEX regulations category 1D and 2D for installation in Zones 20, 21 and 22.
With the lid closed and the cable fixed the degree of protection achieved is IP67.
Three different process connections are available, inch threads, NPT and tri-clamp.
Standard models can withstand up to 25bar pressure, which opens up the possibility for further applications.
Further reading
Capacitive sensors have measure of accuracy
Sensing distance indication (Si) is a new option available with the capacitive high performance sensors from Rechner.
Capacitive sensors claim top performance
Rechner reckons its High Performance sensors are very different from any other capacitive sensor on the market.
The heads are available in stainless steel or aluminium as a lower-cost option.
The Rechner capacitive probe is different.
Consider the main advantage of capacitive sensors: the ability to sense any media.
Now remove all the disadvantages of capacitive sensing, such as: effects of changing ambient conditions, changing media, media sticking to the probe and problems with very low core density powders that have a low dielectric constant.
The result is the Rechner PER level probe.
The PER level probe works on the "three-electrode" principle.
Each measuring point has two electrodes, a measuring electrode and a screen electrode that surrounds the measuring electrode.
The walls of the container, assuming the vessel is metal, become the third electrode.
If the vessel is nonmetallic then a metal strip must be placed down the side of the vessel.
The output is balanced when the container is empty by using a potentiometer on the remote evaluation unit, or within the head depending on version.
The output is only switched when there is a direct line of contact from the measuring electrode to the container wall.
As soon as the level falls below the set measuring point there will be no output, even if the media is a paste or cream and sticks to the probe.
There will be no output because there is no direct line to the container wall and the field lines cannot pass by the screen electrode.
A key benefit of the Rechner probes are their suitability for all media, from low dielectric constant materials such as plastic powders, through to acids.
They are even suitable for creams and pastes as product build up has no significant effect on the switching point.
A change in ambient conditions within the vessel concerned will also have no effect on the switching point.
If the process requires continual monitoring the true level probe gives an analogue output throughout the customer specific measuring range.
The PER level probes allow for up to three measuring points within the one probe when using a single evaluation unit or even more with the use of an additional slave unit.
With temperature ranges up to 250C and a variety of housing materials including PTFE, Rechner level probes are suitable for most industries, including the control of hot melt glue.
The end user can now choose between using a remote evaluation unit, and having the stand-alone unit with a stainless steel or aluminium head.
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