Frequently asked questions about using capacitive sensors are looked at in this section.
Capacitive sensors offer many advantages over traditional mechanical switches.
Comparison of capacitive sensor vs. mechanical limit switch
|Comparison||Capacitive Sensor||Mechanical (Limit) Switch|
|Fast signal processing||The electrical output signals can undergo further processing directly in electronic circuits.||Issues a mechanical signal, which is then transmitted electrically, hydraulically, pneumatically, or mechanically as required.|
|Noncontact detection||Operation without touching the objects being measured.||Operation only possible with mechanical contact: objects to be measured can be manipulated or obstructed.|
|Quick detection||Quick detection and thus short response and switching times, i.e., high switching frequencies are possible.||The mechanical sequence takes time and sets narrow limits on the maximum switching frequency.|
|Maintenance-free working||There are no moving contacts that can become contaminated or worn.||Mechanical contacts can become contaminated and worn over time. The contact transition resistances can change unpredictably.|
|Reliable signal generation||The electronic output prevents contact bounce.||Contact bounce may occur at signal output. As a result, a mechanical contact may supply multiple switching pulses per switch event.|
|Low energy consumption||Very small switching currents are also possible.||The contact resistance and the risk of oxidation of the contact surface mean that a certain minimum current is necessary.|
Simple integration into an application
|No calculation of the start-up curve is necessary.||The start-up angle and start-up path must be calculated. Depending on the direction of actuation, different mechanical versions of the switch lever are required.|
The wear resistance means that the switch points remain stable over time.
The number of switching cycles therefore does not affect the sensor service life.
Mechanically moving parts of the switch are subject to wear and lead to switching errors.
This means that the switching rate limits the switch service life.
|Applications with little space||Extremely compact designs are possible.||There are structural limits to the implementation of compact designs.|
special designs as required
One design available for use in different applications requiring different movements.
Numerous sensor designs are available.
|Different applications require completely different designs or various sensing elements (rollers, tappets, levers, etc.).|
Check all settings, properties, and distances relating to the sensor and the target. In particular ...
Check the sensor and the ambient conditions for possible interference.
In particular ...
Unfortunately, we cannot give a definitive answer to this question. Reason …
This is because the composition of cleaning agents, coolants, and lubricants, i.e., the formulation, is known only to the relevant manufacturer. Lubricating oils usually contain additives, which, even in small quantities, can change the chemical behavior of the lubricating oil. Even if the sensor housing material specified in the technical data promises to be oil-resistant, the additives can make the lubricant aggressive as a whole.
It is therefore essential to carry out your own tests to check chemical compatibility. Please note that the manufacturer of a cleaning agent, coolant, or lubricant can change its formulation without notice. This can cause a combination of materials that has worked for a long period of time to suddenly stop working.
The new EU Directive 2014/34/EU provides clear information in this regard under Article 41, paragraph 2, and states that EC-type examination certificates issued under EU Directive 94/9/EU remain valid.
Article 41 Transitional Provisions
(1) Member States shall not impede the making available on the market or the putting into service of products covered by Directive 94/9/EC which are in conformity with that Directive and which were placed on the market before April 20, 2016.
(2) Certificates issued under Directive 94/9/EC shall be valid under this Directive.
Capacitive sensors according to NAMUR from Pepperl+Fuchs are suitable for use in Class I - III, Division 1; see the information in the Control Drawing, which can be downloaded from the Pepperl+Fuchs website.
Background knowledge ...
NEC 500 is a combination of the designation for the only legally binding standard for electrical equipment in the USA (the NEC) and an article (500) thereof. The abbreviation "NEC" stands for National Electrical Code and is considered law in the USA as NFPA 70 (National Fire Protection Association No. 70). Article 500 of this Code describes the classification of explosion-hazardous areas according to Classes and Divisions in the USA. Similarly to the zone classification according to Directive 2014/34/EU in Europe, plants are divided into different areas—Classes and Divisions—according to the duration and frequency of the occurrence of a hazardous potentially explosive atmosphere.
The various connection types can be quickly identified by referring to the type code.
|Connection Type||Sensor Identification (cf. Type Code)|
|Fixed cable||Sensor without connection identifier at the end of the order designation.|
|Connector||One of the following connector identifiers at the end of the order designation: "V1", "V3", "V5", "V13", "V16", "V18."|
Take a look at the range of Pepperl+Fuchs capacitive sensors.