force can produce a variety of physical effects, various principles and may employ different processes for different sensor designs require manufacturing capacity. Force sensors are: (1) the measured force of the elastic member (such as a spring, beam, bellows, diaphragm, etc.) to produce the corresponding displacement signal is obtained by measuring the displacement force. (2) an elastic member and the strain gauge constitute the sensors, strain gauges firmly attached to the surface member. Deforms the elastic member when a force, the resistance value of the strain gauge changes (strain occurs, the strain gauge geometry and resistivity change, a change in the resistance value), the force signal obtained by resistance measurement. May be made of a metal foil strain gauge, it may be made of a semiconductor material. (3) the load by the piezoelectric effect. A force by a piezoelectric crystal direct conversion of the potential difference across the electrodes disposed on both sides of the crystal. (4) the force due to changes in the natural frequency of the mechanical resonant system to obtain information force by frequency measurement. (5), the information obtained by the associated electromagnetic force balance parameters by balancing the force of the electromagnetic force to be measured.
in the tube wall or affixed two four strain gauges attached to the half of the solid portion as a temperature compensating plate the other half as a strain gauge measurement. When no pressure is full bridge circuit consisting of four strain gauge balance; when pressure is applied to the lumen, is deformed into a cylindrical "drum-type", so that the bridge is out of balance, the pressure output into a voltage of a certain relationship. Such a sensor may also be tested by the piston to the pressure transducer is transmitted to the strain measured pressure drum or transfer through the membrane catenary shape of the force. Simple tubular strain pressure sensor structure, ease of manufacture, applicability, has wide application in terms of dynamic pressure measurements rockets, artillery shells and.
its elastic sensitive element fixed to the periphery of a circular metal flat diaphragm. The diaphragm is deformed under pressure, at the center of the radial and tangential strain and strain reaches a positive maximum, the radial edges of the strain reaches maximum negative value, zero tangential strains. Thus often the two strain gauges are attached to the positive and negative maximum strain at the half-bridge circuit and connected to the arm adjacent to obtain greater sensitivity and temperature compensation. With circular foil strain gauge (see resistance strain gauge) is able to maximize the use of the strain effect of the diaphragm. Nonlinear such sensors more significant. New products diaphragm pressure sensor is sensitive elastic element and strain gauges set in a single crystal silicon film, i.e., using integrated circuit technology create the diffusion resistive strip on a monocrystalline silicon diaphragm, and the peripheral fixed structure manufactured using into a solid state pressure transducer (see piezoresistive sensor).
measuring small pressure, the structural strength can be fixed beam or beams and the like. One method is to use a diaphragm pressure into the dowel through the force transmitted to the strain beam. The maximum strain of beam fixed at both ends in FIG. 3 at both ends and the midpoint of the beam, strain gauges attached to it in these places. There are other forms such a structure, for example, may be employed with cantilever diaphragm or bellows configuration.
in a combined strain pressure sensor, the sensitive element can be divided into the elastic member and the elastic strain element feel. The pressure converter element feel the force transmitting member to the elastic strain strain most sensitive parts, the strain gauge is attached to the elastic strain of the maximum strain element. Indeed more complex tubular strain and strain beam are of this type. Feeling element having a diaphragm, diaphragm, bellows, Bourdon tubes, an elastic strain element with a cantilever, a fixed beam, [pi girder, an annular beam, the thin-walled tube and the like. Therebetween may be combined into a variety of different types according to needs. Gauge pressure sensors are used to measure the dynamic or static pressure of the flow medium, for example gas or liquid pressure power export pipeline equipment, engine manifold pressure and the like.
to improve the accuracy of the force sensor - Compensation
strain signal will cause the temperature of four strain gauges (resistance) and the degree of change in the same direction. Because the two positive and two negative strain strain is included in the equation, the temperature will not produce an output signal.
remaining small residual error can be corrected by connecting to a special Wheatstone bridge nickel.
Further, the strain gauge temperature compensation is required sensitivity (TCS). When the temperature changes and the like, E modulus of the material will decrease, resulting in a strain. Further, the strain gauge temperature-dependent sensitivity. Compensating resistor at high temperatures will produce a greater pressure drop. This will reduce the output signal of the Wheatstone bridge.
in the loaded state, linearity errors will also change. This can be accomplished by optimizing the elastomeric materials and structures, and select a precise measurement point.
FIG presents summary compensation method. In addition TKzero TCS and described above, can also be compensated for by adjusting the linearity and sensitivity.
in the form of the load cell weighing choice depends on the type of installation and space, ensure proper installation, safe and reliable weighing; other hand, to consider the manufacturer's recommendations, in terms of the sensor manufacturer, it is generally predetermined force the material sensor, the performance, installation form, structure, elastomeric Wait. Such as aluminum cantilever sensor suitable for electronic price scale, platform scales, scales and other text; cantilever-type steel sensors are suitable for electronic belt, catchweigher like; steel sensors are suitable for bridge track scale, truck scale; column load cell suitable for truck scale, dynamic railroad scale, hopper scales and other large tonnage. Load cell used in a variety of electronic scales, industrial control, line control, overload alarm safety, material testing machine, and other fields. Electronic truck scale, electronic scales, electronic truck dynamic axle load scales, electronic hook scales, price computing scale, electronic scales steel, electronic track scale, hopper scales, batching scales, scales, and other canned.
how to replace the force sensors
In actual use, the load cell, sometimes encountered overload, impact, resulting in plastic deformation sensors, influence measurement accuracy, severe, can also cause damage to the sensor, does not work properly, then you need to replace the sensor. At this point we should be how does it work? Replacement when it comes to what issues need attention? The following experts on this issue and to share with you. Load cells can be replaced on the premise that the force applied to the force axis coincident with the axis of the sensor, which is the first point. With the increase in the rated load, the load cell output microvolts / division signal is decreased rather than increased as the rated load, the output signal also increases. This point is often overlooked. Therefore, when replacing the sensor, and the sensor should be same as the original loading as possible. To replace the slightly larger payload, we should note scale electronic weighing instrument adjustability range: If it is not adjustable old indicator, because a large load replaced sensor output microvolts / division signal small, not full-scale output, display, DIP reach adjustment purposes can not be used; if adjustable range of the load cell, the load into the larger sensor can be set by the range, according to the instructions debugging use. Also note that, if the rated load sensor is too large, the output microvolts / indexing signal is too small, easy to reduce the sensitivity of the scale. For electromechanical sensors mounted in the second S-shaped force transmission link binding scale, it should be noted: reinstalling the link length after the sensor consistent with the original link length. On the other hand, it is to ensure that the first force transmission lever is horizontal and perpendicular to the first linkage force transmitting lever 90 degree angle. If there are deviations, it will directly affect the accuracy and sensitivity of the scale. Link is too long, it will be a "large scale" phenomenon; too short, there will be "small scale" phenomenon. It should also be noted that at this time, the link must be in the free hanging state, not friction with other objects, so as not to affect the sensitivity of the scale. Debug combined organic scale replacement of the sensor, it will be carried out in the specification in a mechanical weighing scale indicator based on accurate debugging. Whether electronic or mechanical and electrical integration scales scales, after the replacement of the sensor must be qualified before use after test. In addition to the above scheme generally effective against load cell, but also effective for the S-shaped sensor. The weighing sensor needs to be replaced often encounter when in use, just follow the above operation, even if the replacement will not have sensors to measure impact.