General principles of work of measuring transducers, sensors
In exact sense of word a measuring transducer is a device which will transform the change of one size in a change other. In terms of electronics a measuring transducer is determined usually as a device, transducers an unelectric physical size (called a physical measurand) in an electric signal, or vice versa. Present, certainly, and exceptions from this rule.
It is necessary from here, that measuring transducers, sensors are used in the electronic systems, i.e. in technical devices p. by an electric signal, representing the result of measuring or supervisions. On the other hand, a measuring transducer can be used on the output of the system, that, say, to generate mechanical motion depending on an electric managing signal. The example of realization of transducers is the system in which a microphone (entrance transducer) converts a sound (physical measurand) into an electric signal. The last increases, and then acts on a loud speaker (output transducer), playback a sound substantially more loud, than that which is perceived by a microphone.
Enough an often measurand according to her determination is simply measured by the electronic system, and the got result is only represented or memorized. However on occasion measuring form the entrance signal of managing chart, which serves either for adjusting of measurand in relation to some Pre-set level or for a management a variable by a size in accordance with measureable. In spite of obvious partial duplication of measuring transducers in these two examples, it is accepted to distinguish these areas of the use of transducers, naming them accordingly control and measuring equipment and managing.
In turn, these two areas are subdivided into a telemetric control and measuring equipment (in which the measuring systems are used jointly with radioline, connections between a transducer and display of data devices), chemical analysis (for which the system is used in an order to define and represent relative maintenance of making mixture of matters), management (in which a productive process, for example rent became, is controlled and managed) process et cetera
Examining flow diagrams control and measuring and managing systems it is necessary to be stopped for next main moments.
A measurand is a subject to measuring physical size, for example: acceleration, moving, force, expense, level, position, pressure, mechanical tension, temperature, speed etc. It can on occasion measureable be electric size, such, as a current, tension or frequency, which will be transformed in an electric signal, suitable for the use in other parts of the system. Thus a measuring transformer is an electric transducers element.
An entrance transducer, transforming, sensors a measurand in an electric signal, - it a device, suitable for the use in other parts of the system. True, although entrance transducers generate an electric output, exist, however, among them and such which have other nature of output signal, for example pressure of air, but there are a bit such transducers. Transducers with an unelectric output are used as pickoffs of measuring transducers serve for converting of unelectric signal into electric. All functions of transducers are an analog, therefore in general case (after some exceptions) their signals are an analog also.
Flow lines are lines between an entrance transducers and other part of the system. Such lines in strict sense can sometimes and to be not, if, say, an entrance transducers takes place in a few centimetres from other part of the system. If he is situated on other distance from the system, then must be taken step to that flow lines did not influence, or poorly influenced on efficiency of work of the system.
Wherein there are substantial flow lines in the system, one is required or more than cascades of interface of signals, that small output signal of entrance transducers to strengthen, expose to analog-digital transformation, filtration, modulations etc. It is necessary in order that information, given out by a primary transducers, was not lost at the transmission of her to other parts of the system. Such cascades can plug in itself and charts the signal processing in which contained in the signal of entrance transducers data are exposed to digital treatment, and a resulting signal or results of calculations can be represented on a display, memorized or used for a management. The interface of signals can be carried out in a few points of the system.
On occasion enough difficultly to conclude about that, where in the system the analog signals of transducers become data. Therefore it is often impossible to distinguish the cascades of forming of analog signal and processing of data. Fortunately, this distinction is rather significant.
Representing or memorizing devices are devices which display the current value of measurand for comfort of work of operator of the system or memorize corresponding information for her subsequent use.
In the case of the sensor-based system some types of devices, intended for comparison of the processed data with some supporting values and receipt of difference signal are used.
A working on a differences signal output transducers (sensors) is used for a management a measurand.
Surely, made examples of the systems contain not all types of cascades of forming and treatment of signals and does not reflect all modes of operations of the control and measuring and managing systems.
In general speaking, principles of work of entrance and output transducers are enough simple. Certainly, their office hours substantially differ from each other - entrance transducers are usually used for transformation of changes of measurand to the weak electric signal, and output transducers will transform a powerful signal in the strong moving. On this account it is necessary to examine two different types of devices, sensors.