Mechanics sensor type is many, like resistance strain gauge pressure transmitter, semiconductor strain gauge pressure transmitter, pressure anti- pressure transmitter, inductance type pressure transmitter, electric capacity type pressure transmitter, resonant type pressure transmitter and electric capacity type acceleration instrument and so on. But applies widely presses the anti- pressure transmitter, it has the extremely low price and a higher precision as well as a better straight characteristic. Under we mainly introduce this kind of sensor.

When has decompressed the anti- strength sensor, we first know resistance strain gauge this kind of part. The resistance strain gauge will be one kind was measured on the strain change will transform into one kind of electrical signal the sensitive component. It presses one of anti- strain sensor main constituents. The resistance strain gauge applies most is the metal resistance strain gauge and the semiconductor strain gauge two kinds. The metal resistance strain gauge also has the filiform strain gauge and the metallic foil shape strain gauge two kinds. Usually is through special sticks the strain gauge the composition close agglutination in to produce in mechanics strain substrate, when the substrate stress has the stress variation, the resistance strain gauge also together has the deformation, causes the strain gauge the resistance number to have the change, thus makes to add the voltage changes in the resistance. This kind of strain gauge when stress produces the resistance number change is usually smaller, the common this kind of strain gauge all composes the strain electric bridge, and carries on the enlargement through the following measuring appliance amplifier, again transmits for processes the electric circuit (usually is the A/D transformation and CPU) demonstrates or the implementing agency.

Metal resistance strain gauge internal structure

Like chart 1 shows, is the resistance strain gauge structure schematic drawing, it by the substrate material, the metal strain silk or the strain foil, the insulation protection piece and the lead-out wire and so on partially is composed. According to the different use, the resistance strain gauge resistance number may design by the designer, but the resistance value scope should pay attention: Resistance number too small, needs actuation electric current too big, simultaneously the strain gauge gives off heat causes itself hyperpyrexia, in the different environment uses, causes the strain gauge the resistance number change too in a big way, output zero drifting obvious, adjusts the null circuit too to be complex. But resistance too big, impedance too high, the anti- outside electronmagetic interference ability is worse. Generally is several dozens ohms to several dozens kiloohms about.

Resistance strain gauge principle of work

The metal resistance strain gauge principle of work is the adsorption the strain resistance has the resistance number change phenomenon on the substrate material along with the mechanical deformation, is named for the resistance strain effect. The metallic conductor resistance value may use the type to indicate that,

In the formula: Rho - Metallic conductor electronic resistivity (Omega cm2/m)
S - conductor cross-sectional area (cm2)
L - conductor length (m)

We take the tinsel strain resistance as the example, when tinsel exogenic process, its length and the cross-sectional area can change, may be very easy from on in the formula to see, its resistance value namely can have the change, if the tinsel is elongated the exogenic process time, its length increases, but the cross-sectional area reduces, the resistance value then can increase. When the tinsel is compressed the exogenic process, the length reduces but the section to increase, the resistance value can reduce. So long as determines adds (usually is surveys resistance beginnings and ends in the resistance change voltage), then obtains the strain tinsel the strain sentiment

2nd, ceramics pressure transmitter principle and application

The corrosion resistance ceramics pressure transmitter does not have the liquid the transmission, the pressure direct action in the ceramic diaphragm front surface, causes the diaphragm to have the small deformation, 厚膜 resistance printing in the ceramic diaphragm back, connects to favor the Stone electric bridge (to shut bridge), because presses the sensitive resistance the pressure anti- effect, causes the electric bridge to produce to have the direct ratio with the pressure highly the linearity, also has the direct ratio with the excitation voltage the voltage signal, the standard signal differently demarcates according to the pressure measuring range is 2.0/3.0/3.3 mV/V and so on, may to be compatible with be supposed the variant sensor. Demarcates through the laser, the sensor has the very high temperature stability and the time stability, the sensor brings temperature compensation 0 ~ 70 �? and may with the overwhelming majority medium direct contact.

The ceramics are one kind of recognition high elasticity, the corrosion resistance, the anti- attrition, the anti- impact and the vibration material. The ceramic heat-stable characteristic and it 厚膜 the resistance may cause its operating temperature scope to reach as high as -40 ~ 135 �? moreover has the survey the high accuracy, the high stability. Insulation degree >2kV, the output signal strong, the long-term stability is good. The high characteristic, the low price ceramic sensor will be the pressure transmitter development direction, has in the European and American countries comprehensively substitutes other type sensors the tendency, substitutes the proliferation silicon pressure transmitter in the Chinese also more and more many users use ceramics sensor.

3rd, proliferation silicon pressure transmitter principle and application

Principle of work
Was measured the medium the pressure direct action on the sensor diaphragm (stainless steel or ceramics), causes the diaphragm to produce has the direct ratio with the medium pressure the micro displacement, causes the sensor the resistance value to change, examines this change with the using electricity line, and the transformation outputs to correspond to this pressure standard survey signal.

Schematic diagram

4th, sapphire pressure transmitter principle and application

Using the strain resistance type principle of work, uses the silicon - sapphire to take the semiconductor sensitive unit, has the unequalled measurement characteristic.

The sapphire is by the monocrystal insulator elemental composition, cannot have the lag, be weary and the slow change phenomenon; The sapphire must be firmer than the silicon, degree of hardness is higher, does not fear the deformation; The sapphire has the extremely good elasticity and the insulation characteristic (in 1,000 OC), therefore, the use silicon - sapphire manufacture semiconductor sensitive unit, is insensitive to the temperature change, even if under hot conditions, also has the very good operational factor; Sapphire anti- radiation characteristic greatly strengthened; Moreover, silicon - sapphire semiconductor sensitive unit, non- p-n drifting, therefore, fundamentally simplified the manufacture craft, enhanced the duplication, has guaranteed the high end product rate.

The pressure transmitter makes which with the silicon - sapphire semiconductor sensitive unit and changes delivering, may under the worst working condition the normal work, and the reliability high, the precision good, the temperature error minimum, the price is higher than.

The table presses the pressure transmitter and changes delivering to constitute by the double diaphragm: Titanium alloy survey diaphragm and titanium alloy receive diaphragm. Printing has the neterogeny extension strain keen bridge circuit the sapphire thin slice, is welded on the titanium alloy survey diaphragm. Was measured the pressure transmission to receives on the diaphragm (to receive between diaphragm and survey diaphragm with tension bar firm connects in together). Under the pressure function, the titanium alloy receive diaphragm has the deformation, after this deformation by the silicon - sapphire sensitive unit sensation, its electric bridge is output can change, the change scope with was measured the pressure has the direct ratio.

The sensor electric circuit can guarantee the strain bridge circuit the power supply, and transforms the strain electric bridge unbalanced signal for the unified electrical signal outputs (0-5, 4-20mA or 0-5V). In certainly presses the pressure transmitter and changes delivering center, the sapphire thin slice, with the ceramic base extremely glass 焊料 connects in together, played the elastic part role, was measured the pressure transformed into the strain gauge deformation, thus achieved the pressure survey the goal.

5th, piezoelectricity pressure transmitter principle and application

In the piezoelectric pick-up the main use piezoelectricity material includes the quartz, the potassium tartrate sodium and the phosphoric acid dihydro amine. Quartz (silicon dioxide) is one kind of natural crystal, the piezoelectric effect is discovers in this kind of crystal, in the certain temperature range, the piezoelectricity nature always exists, after but the temperature surpasses this scope, the piezoelectricity nature completely vanishes (this high temperature is so-called "Curie temperature"). Because along with the stress change electric field change small (also said piezoelectric modulus quite is low), therefore the quartz gradually is substituted by other piezoelectric crystals. But the potassium tartrate sodium has the very big piezoelectricity sensitivity and the piezoelectric modulus, but it only can only then can apply under the room temperature and the humidity quite low environment. The phosphoric acid dihydro amine belongs to the artificial crystal, can withstand the high temperature and the quite high humidity, therefore already obtained the widespread application.

Now the piezoelectric effect also applies on the polycrystal, for instance the present piezoelectricity ceramics, including the barium titanate piezoelectricity ceramics, PZT, the niobate are the piezoelectricity ceramics, niobium magnesium sour lead piezoelectricity ceramics and so on.

The piezoelectric effect is the piezoelectric pick-up main principle of work, the piezoelectric pick-up cannot use in the static survey, after because the process exogenic process electric charge, only has has in the return route 无限�?when input impedance only then obtains the preservation. The actual situation is not such, therefore this had decided the piezoelectric pick-up only can survey the dynamic stress.

Piezoelectric pick-up main application in acceleration, pressure and strength and so on in survey. The piezoelectricity type acceleration instrument is one kind of commonly used accelerometer. It has the structure simply, the volume young, the weight light, the service life is long and so on the outstanding characteristic. The piezoelectricity type acceleration instrument in the airplane, the automobile, the ships, the bridge and in the building vibration and the impact survey already obtained the widespread application, specially in the aviation and the astronavigation domain has its special status. The piezoelectricity type sensor also may use for to survey the engine interior combustion pressure the survey and the vacuum degree survey. Also may use in the war industry, the change and the artillery mouth shock wave pressure which in the chest cavity for example surveys the gun artillery bullet with it which to fire the flash chest cavity presses. It already may use for to survey the tremendous pressure, also may use for to survey the small pressure.

The piezoelectricity type sensor also widespread application in the biomedicine survey, for instance said the ventricle drive pipe declines