Brochure/Catalogue

Glossary
P
Passive isolator/ input loop powered Generates its power supply from the input signal (0/4–20 mA).
The amount of current needed internally is so small that the measurement signal
is not inuenced. Transformers are used to provide the isolation between the
input and the output.
The advantages include: eliminates the inuence of the mains power system,
highly accurate, minimal signal delay, and minimal power used. Passive isolators
do not function free from feedback;
so a load change on the output circuit will automatically effect the input circuit
as well.
Passive sensor Contains passive components whose parameters can be changed by the
measured variables. A primary electronic mechanism converts these parameters
into electric signals. An auxiliary external power source is needed for the
passive sensor. Passive sensors can be used to determine both static and
semi-static measured variables. For this reason, the majority of sensors have a
passive construction. Examples of this type include load cells and resistance
thermometers.
Pollution severity level The pollution severity level species the conditions of the immediate
surroundings. It is dened in DIN EN 50178, Section 5.2.15.2.
The pollution (contamination) severity level should be used to determine the
required creepage distance for the insulation. Pollution degree 2 is the default
specication.
• Pollution severity level 1
There is no contamination or only dry occurrences of non-conductive pollution.
This pollution has no inuence.
• Pollution severity level 2
There is only non-conductive pollution. Temporary occurrences of conductivity
caused by condensation may also occur.
• Pollution severity level 3
Conductive pollution or dry, non-conductive pollution that can become
conductive due to condensation is likely to occur.
• Pollution severity level 4
The contamination leads to continual conductivity which can be caused by
such contaminants as conductive dust, rain or snow.
R
Rated voltage Specied by the insulation coordination – the rated voltage is the voltage level
at which the product can be safely operated, in relation to the corresponding
pollution severity level and the surge voltage category.
Relative humidity The relationship between the actual moisture and the maximum possible
quantity of water in the air. Expressed as a percentage.
W
Technical appendix/Glossary
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