Design of High Precision Electronic Scale Based on MSP430G2

The resistance bridge is used as a pressure sensor, when the external force is applied to generate 0 ~ 20mV voltage small signal, the precision instrumentation amplifier amplification 51 times, access to 16 bit high precision digital analog conversion (A/D) chip ADS1146. 16 bit A/D in the input voltage of 3.6V, the minimum resolution of 0.05mV, to achieve high precision pressure sensor signal acquisition, the accuracy can reach 0.1 grams. The A / D conversion to digital quantity through the SPI interface connected to the low power microprocessor msp430g2553, and then sent to the LCD display, through the calibration button and do some simple multiplication and achieve more functional. Test results show that the small signal amplification link can achieve the stability of the signal amplification, and can achieve accurate weighing. Introduction How to detect the weak electrical signal is a problem that the hardware circuit designer must consider. In real life, we often to detect the pressure signal. Usually the pressure sensor is a resistance bridge, there are four internal resistance. When there is an external force and deformation sensor. Under the external force of bending, and the upper end of the elongated, lower pressure was short, one end of the elongated with proportional corresponding resistance value, stub end in negative proportion to reduce the corresponding resistance value. Because of the changes in resistance, the voltage output of a bridge pressure is 0 ~ 20mv. To collect the voltage must be to carry on the effective amplification, early amplified when people used LM324 op amp amplification cannot collect signals effectively. And interference particularly large, accuracy is not up to the requirements. In this design, a new type of high precision instrumentation amplifier INA128 is used to amplify the signal by 51 times, which has high common mode rejection ratio, and can effectively restrain the interference by using differential input. The amplified signal is connected to the high precision 16 bit A/D for signal acquisition, and the converted signal is connected to the low power consumption microprocessor MSP430G2553 for processing. Can achieve high precision weighing.