The general sensitivity of the high-range accelerometer is about 1 mV. If the acceleration signal is in the range of 1g to 10g, the output of the sensor is between 1 mV and 10 mV. The noise of the traditional test system may cover such a small voltage signal, then The complete acceleration signal will not be detected, which will cause deviations in the analysis of the test results. Under the condition of selecting high-range acceleration sensor, the adaptive digital sensor can automatically adjust the test gain according to the amplitude of the acceleration signal, maintain the complete output of the acceleration signal, broaden the dynamic test range, and realize the digitized and intelligent measurement of the acceleration sensor. aims.
1. Design scheme 1.1 Overall design of the systemThe adaptive digital sensor is mainly composed of two parts: the adaptive acquisition system and the experimental verification system. The adaptive acquisition system is the core module of the digital sensor. The overall structure of the system is shown in Figure 1.
The adaptive acquisition system dynamically adjusts the gain based on the amplitude of the input signal and acquires, stores, and transmits the conditioned signal. The core of the collector uses the FPGA as the main controller to ensure the fastness, real-time and flexibility required by the collector.
The experimental verification system can synchronously collect the measured signals, verify the acquisition results of the adaptive dynamic signal collector, and restore the data collected by the adaptive digital sensor to the original signal. The verification system is based on an industrial-grade computer and is equipped with a high-speed synchronous RS422 communication card and an analog data acquisition card. This can meet the requirements of the rapidity, synchronous communication, large-capacity storage, and analog direct acquisition required for the verification system.
1.2 Programmable Amplifier DesignTo achieve small signal acquisition, it is necessary to split the voltage signals of different amplitudes, which is the function of the program-controlled amplifier. The programmable digital sensor's programmable amplifier uses the AD8251 and AD8253 cascaded, as shown in Figure 2. Among them, the input signal is input to the "IN+" input terminal of the process control amplifier, and is output through "OUT".
The optional magnification of the AD8251 is 1, 2, 4, and 8. The optional magnification of the AD8253 is 1, 10, 100, and 1000. The combination of the two is 1, 2, 4, 8, and 10. 20, etc.; the magnification of the two is adjusted by four control terminals 1A0, 1A1, 1A2, 1A3, and the gain of the programmable amplifier is set according to the range of the input signal, as shown in Table 1.
The gain automatic switching control is the core module of the adaptive digital sensor. The gain selection is automatically completed by the automatic gain switching control module inside the FPGA. The automatic gain switching is based on the amplitude of the external input analog signal to automatically select the appropriate gain to ensure The measured value has sufficient resolution and accuracy. During the system power-on operation, the internal gain automatic switching control unit of the FPGA will compare each sampling point of A/D. When the voltage is higher than the threshold voltage, it will enter the higher threshold voltage comparison, lower than the threshold voltage. When the time is entered, the threshold voltage comparison of the lower level is entered, and finally the corresponding gain is performed according to the gain position.
The workflow of the program-controlled amplification module is shown in Figure 3.
Set the gain of the PGA to 1 before each sampling, and perform AD conversion on the signal under test, and reset the gain of the PGA according to the result of the AD conversion. Perform AD conversion on the adjusted signal under test and store the data obtained by AD conversion.
3. Adaptive digital sensor dynamic test 3.1 Test principle, method and stepsThe experimental principle is that the adaptive digital sensor automatically adjusts the gain of the programmable amplifier according to the output voltage of the acceleration sensor, collects and stores the adaptive sensor signal, and uploads the data to the verification system, and the verification system synchronizes the collected data and adaptive acquisition. The data is compared and verified, and the adaptively acquired data is restored.
The test method is to place the acceleration sensor on the shaking table experimental platform, simultaneously record the output signal of the acceleration sensor with a multimeter, an adaptive digital sensor and a verification system, and restore the data collected by the adaptive digital sensor to an actual signal. The performance of the adaptive digital sensor is analyzed based on the measurement results. The ambient temperature is measured from 20 ° C to 25 ° C and preheated for half an hour before each measurement starts. The test procedure is as follows:
(1) The acceleration sensor is placed in the vibration table, the frequency of the vibration table is set to 1 kHz, and the amplitude of the acceleration signal is changed according to the set parameter, thereby changing the output signal of the acceleration sensor;
(2) Loading the acceleration signal to the test rig according to the rotation speed of the ion fan, recording the output of the sensor through a multimeter, and collecting data by using the high-resolution acquisition card provided by the adaptive digital sensor and the verification system;
(3) The verification system restores the acceleration sensor output voltage signal based on the data acquired by the adaptive digital sensor.
The accelerometer indicators used are as follows:
Range: ± 5 000 g
Sensitivity: 1.098 mV/g
We are professional audio manufacturing company that makes a variety of speaker with bluetooth, including bluetooth portable speaker, bluetooth speakers outdoor, small speaker bluetooth, light bluetooth speakers, waterproof speakers etc.
With full turnkey service from product design to delivery, and every step in between.
From sophisticated custom audio systems to 'off-the-shelf' speaker drivers, iTopnoo has been saving our customers time, effort, and money.
To constantly offer clients more innovative products and better services is our consistent pursuit.
Best Portable Speakers,customizable bluetooth speaker, Custom jbl speakers, speaker wholesalers
TOPNOTCH INTERNATIONAL GROUP LIMITED , https://www.mic11.com