Digital electronic scale ----- Digital Electronic Scale

Digital electronic scale, Digital Electronic Scale Keywords: digital electronic scale The digital electronic scale introduced by this paper has high accuracy, easy to make, low cost, compact size, practical. Its resolution is 1 gram, and the measurement accuracy can be 0.5% RD + -L word in the range of 2 kg. (1) Working principle The principle of digital electronic scale circuit is shown in the figure, and its main portion is a measurement amplifying circuit composed of resistance strain sensors R1 and IC2, IC3, and a number display table consisting of IC1 and peripheral components. The sensor R1 employs E350 to ZAA foil resistance strain sheet with a normal resistance of 350o. The measurement circuit converts the resistance of the R1 to the voltage signal output. The IC3 enlarges the converted weak voltage signal as an analog voltage input of the A / D converter. IC4 provides l. 22V reference voltage, which simultaneously passes the reference voltage of the A / D converter after voltage R5, R6 and RP2. 3-1 / 2 bits A / D, the reference voltage of the converter ICL7126 is introduced by the RP2 intermediate contact, and the negative end is introduced by the intermediate contact of the RP3. The reference voltages between the two ends can make the sensor nonlinear error to compensate. Be (2) component selection l. IC1 uses ICL7126 integrated block; IC2, IC3 uses high precision low temperature standard precision op amp-07; IC4 uses LM385-1.2V integrated blocks. 2. The sensor RI is selected from the E350-ZAA foil resistance strain sheet, its normal resistance is 350o ,. 3. Each resistor element should be used for precision metal film resistance. 4. RPI selects a precision multi-zip potentiometer, RP2, and RP3 can be replaced with precision metal film according to precision metal film. 5. C1 is used in the capacitor to select a mica capacitor or a ceramic capacitor. (3) Production and debugging The digital display electronic scale profile can be referred to in the form of the figure. Among them, the shape of the steel piece can be made by ordinary steel saw blade, and the method is: first polishing the sawtooth is flat, and then the saw blade is heated to micro-red, and the heat is processed into "U" shape, and drilled in the corresponding position for later installation. Then heaten it to orange (seven or eight hundred degrees Celsius), quickly release the cold water to improve the hardness and strength, and finally perform a surface treatment process. The scale hook can be bonded to the bottom of the steel parts. The strain sheet is bonded to a portion of the deformation of the steel parts (inward) with a special strain adhesive. At this time, its stress change is just the opposite of the resistance change. The ring application activity chain is connected to the weaner to use the scales to hang it, while the ring should also be on the same vertical line with the scale hook. During the debugging, 1 kg and 2 kg standard weight should be prepared, and the process is as follows: 1. First adjust the RP1 when the scale body is naturally sagging no load, so that the display accurately displays zero. 2. Adjust the RP2 to make the weighing body with the full range weight (this circuit is selected from the range of 2 kg). 3. Then hang a standard weight of 1 kg under the scale hook, see if the display shows 1.000, if there is a deviation, adjustable The RP3 value makes it accurately displayed 1.000. 4. Re-performing 2, 3 steps to meet the requirements. 5. Finally, the RP2, RP3 resistance value is measured, and is replaced with a fixed precision resistor. RP1 can take out the end of the field adjustment. Adjust the RP1 before the measurement is measured back to zero the display.