Device of ohmic sensors
Adjustable ohmic resistance can be rassmatyorivat as the movement sensor.
The rheostat can be such sensor.
Really, when moving the toddler of the rheostat its resistance changes.
Here movement of the toddler yavyolyatsya by entrance size, and the size of the omichesyoky resistance of the rheostat included in the chain — output size. In sensors of rheostatic type, besides, between movement of the cursor and the izyomeneniye of resistance there has to be the certain unique dependence.
Yavyolyatsya by basic elements of the rheostatic sensor (fig. 1a): 1 — the framework; 2 — resistance applied on it in the form of winding from the wire, the semiconductor or any other carrying-out material; 3 — the mobile brush, skolzyayoshchy on the surface of resistance or on the number of the contacts connected to it.
In fig. 1 ohmic sensors of 2 types are shown: a) with besyostupenchaty multireverse winding; b) with sectioned winding.
In sensors to sectioned resistance at the peremeyoshcheniye of the brush there is the step change of resistance while in the sensor with stepless winding rather smooth.
Advantage of sensors with the sectioned resistance is the opportunity to manage big currents. It obespechiyovatsya by the fact that work of contacts of such sensors thanks to availability of bypass resistances happens in the most blagoyopriyatny mode.
The characteristic of the linear rheostatic sensor has the appearance
- Rx = (R: L) x, where;
- Rx — resistance included in the chain (ohm);
- L — the full length of winding (cm);
- R — the total resistance of winding (ohm);
- x — movement of the brush (cm).
If the rheostatic sensor is switched on according to the scheme of the potentiometer, then it carries the name of the variable potentiometer transducer. In fig. 2 the scheme of turning on of such sensor is shown. Here the size of the napryayozheniye removed from the rheostat depends on the provision of the cursor. Really, if the cursor of the potentiometer is in extreme left situation, then Ux stress removed from it will be miyonimalny (almost equal 0). In process of movement of the cursor to the right the removed stress will increase, and it will be equal to tension on source clips, i.e. UX=U in extreme right situation.
So, tension on the voltmeter V will be in lineyyony dependence on the provision of the cursor of the potentiometer;
Ux = U (x: l)
Structurally rheostatic sensors are carried out as sensors angular and sensors of linear movements
Ohmic sensors are simple, reliable in work and therefore they are doyovolno widespread in the equipment as elektrichesyoky sensors of mechanical movements, in the remote sleyodyashchy drive and in computing devices.
The error of reostatyony sensors is defined by gradualness of change of resistance, change of resistance of winding from temperature, inaccuracy of technology process of production (frameworks, winding, cleaning of the kontaktyony path).
For measurement of razviyovayemy efforts the coal datyochik which also sleduyot finds application to carry to group of omiyochesky. It allows to preyoobrazovyvat the effort transferred to it in electrical resistance. The coal sensor (fig. 3 and) gathers from graphite disyok in the column.
On the ends of the column contact disyok and the emphasis through which pressure upon disks is transmitted are located. Elektriyochesky resistance of the coal sensor consists of resistance of disks and transition contact resistances between coal disks. The size of the transitional contact soprotivyoleniye depends on the size of the squeezing force. The more force squeezing coal disks, the contact resistance are less.
The schedule of dependence of resistance of Rugolnogo of the sensor on the made effort of River is provided on fig. 3.Top