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Sensor and Transducer

Sensor and transducer are the component and devices used to measure physical conditions. Transducers convert physical parameters into electrical signal that correspond to. In another word, transducer is a device that receives an energy and then convert to another form of energy.

Sensor has mean more restrictive than transducer, it is a part of a transducer that respond to the measured quantity. But technically sensor and transducer has a same general meaning, and can be use for

There are many kind of familiar transducer that always be used in industry or simple measurement and detection. Sensor for position and displacement, velocity and acceleration, pressure and flow, temperature and so on.

This page gives two example of familiar sensor, i.e.

Sensor for position ( LVDT)
The LVDT is composed of three coils. The central emitter coil, driven with a sinusoidal signal at a frequency between 10 and 20 kHz, mounted between two larger receiver coils; the two receiver coils are identical, counter-wound and connected either in series or in parallel. The emitter is mounted on the IP table while the two receivers are attached on a reference structure; when the emitter is exactly in the mid point between the twin receiver coils, no net signal is induced. When the table movements move the emitter coil in a direction, a sinusoidal signal appears on the receiver coils. This signal has amplitude roughly proportional to the displacement from the center position. If the coil is moved in the opposite direction the sign of the induced sinusoid is changed.

Figure of Principle of LVDT

Sensor for for temperature

Cheap and famous temperature sensor is LM35. The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to +110°C range (−10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.
Features:

• Calibrated directly in ° Celsius (Centigrade)

• Linear + 10.0 mV/°C scale factor

• 0.5°C accuracy guarantee able (at +25°C)

• Rated for full −55° to +150°C range

• Suitable for remote applications

• Low cost due to wafer-level trimming

• Operates from 4 to 30 volts

• Less than 60 µA current drain

• Low self-heating, 0.08°C in still air

• Nonlinearity only ±1⁄4°C typical

• Low impedance output, 0.1 W for 1 mA load

Download LM35 datasheet

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