Different uses may have distance measurements (radial or linear).
This can be from a position feedback of a damper to the point of
a flying saw.
According to use a required distance measurement and whose
positioning are choosed.
Those is very often hooked on because of the required accuracy.
An application is for example a automatic conversion machine.
Those has for the positioning different types of distance measurements .
• position switch
• calculated travel
• incremental rotary encoder (the functional principle is based on the counting out of pulses)
+ position switch
As simplest use are reckoned the position switches. Every chassis requires at least two position switchs, namely end positions. These are required on the one hand as fixed-points and by use of a distance measurement as basing point, where the values of the distance measurement are adjusted with checkpoints.
It is naturally possible that this end positions are also generated because of a analog position feedback. At this you have to mark that there exists a sufficient mechanical safety because otherwise it can come up to a problem. An employment is for this purpose for example a butterfly for the ventilation technology, which is equipped with position feedback however without end positions.
+ calculated path
If a chassis has only position switches, 'cause due to the application is only a driving between these end positions required, there is additional the possibility to assess the current path. Important is at this that the actuation is with consistent speed in use. Otherwise the tolerance between the calculation and the reality is to big. Generally is for this kind of determination of the current path to note that the allowance between debit and actual has to assume with approximately 10 % of the path. More detailed it couldn't be proceed. Mostly this calculation serves only as added information for a process control system where the aggregation has to be arranged approximately.
+ sensor with sensing wheel
The easiest form of a distance measurement consists of a sensor (mostly a inductive proximity switch) and a sensing wheel, which has the form of a gearwheel. The sensor is fix assembled and the sensing wheel on the axle. The sensor is free to detect only the teeth of the sensing wheel. Per positive shoulder depending on operating course a definded path to the current path is added or subtracted. In the end positions the distance measurement can be referenced to adjusted scores. A chassis can be so with easy averages for few centimeters accurate positioned.
+ shaft encoder
In easy applications are shaft encoder assembled. As easiest is reckoned the rotary potentiometer. This is depending on condition of pressure between + / - 10 V announced, which is converted in a path or an angle. This kind of detection is used e.g. at control butterfly valves.
+ incremental shaft encoder
Incremental shaft encoder have already a very high resolution and via signal evaluator can be positioned particulate accurate to a millimeter. Shaft encoder are all over there integrated where via rotation the path can be established. It gives them in any types. As complete apparat the shaft encoder can be assembled already with bus interface. This requires simply the bus cable because the power supply system is taken from the bus.
+ Linear measuring units
For quick however also accurate uses, which can be accomplished linear, can be used linear measuring units. You have to consider that the traverse path can be only as long as the slat. The longer the slat the more inaccurate is again the resolution.
Equal which kind of path detection is choosed now, when an applicable positioning can be for it arranged.
Important is at this only that at the application the least resolution is known. This defines the dead range of the measuring. For that purpose also should rank among the brake ability of the drive. It makes no sense to have an extreme accurate measurement when the drive hunts over the dead range. Although a pre-threshold can be defined, however barely at low lanes this can operate problems, when the drive don't reach the required speed. Then it hasn't the adequate dullness and the drive stays already before the dot to arrive.
For a positioning apply as parameter always the following values:
• dead range: In what the path isn't changed.
• brake area: With a controlled drive is the speed counterbored. This allows a more accurate positioning.
• prior switch-off: With a always same dullness of the drive can the point be adjusted. The drive is already beyond the dead range deactivated and expires to the desired point.
Additional, different monitoring mechanism can be activated. A run control if the way changes enough within a time or if handset limits aren't overtravelled. There is nor additional the possibility to achieve a master / slave (Designated a form of administration for the access of a common resource) commutation, in case there have been installed two distance measurements. These check itself one another. If the reported path differs to excessive, there is a advice applied.
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