A Referential Sensor Input Calibration Technique
The accuracy of the sensor acquiring the signal in the field directly affects the measurement and control accuracy of the entire industrial automation system. In order to obtain the real scene information, it is necessary to transform the analog electrical signal output by the analogue sensor into the computer system without distortion. In this paper, an input calibration technique for force and displacement sensors is proposed, and the hardware gain and channel gain are calculated based on the sensitivity of the ideal sensor. At the same time, the software calibration is carried out. Through the actual engineering verification, this method calibration results accurate, easy to operate, with the value of engineering promotion. 0 Preface In the industrial automation production, automatic control system, non-electric measuring system, widely used a wide range of sensors, measurement and control plays an important role in the process. Whether the sensor obtains the physical signal of the scene correctly or not is directly related to the measurement accuracy of the whole system. 1 Sensor input channel This article only for the analog sensor output analog electrical signals are discussed, does not involve the digital sensor. Generally, the computer system generally accesses the sensor as shown in FIG. 1. Figure 1 sensor input channel Here the force sensor (mostly mV-level signal), for example, first, the sample switch sampling, into the amplifier DC amplification, the final amplified signal is fed into the ADC (analog / digital converter), during the fast transient The signal must also be sampled and held for processing. ADC will amplify the analog voltage signal into a digital signal into the computer system of these digital information, although representing the size of a variety of physical parameter values, still need to go through a scale conversion (engineering transformation), it will be converted into the original The true value of the parameter for display, calculation and processing. To ensure that the computer system can obtain the real detected information in the field and ensure the accuracy of the system, it is necessary to take the distortion-free transformation method to obtain the real information in the field and uniformly calibrate the various links of the sensor input channel. 2 Enter the calibration idea In general, the displacement input has no similar hardware feedback for internal hardware gain. Figure 2 shows the force, displacement sensor input calibration module diagram. Amplification of a typical displacement feedback signal (LVDT or potentiometer style) amplifies the force-sensor-like signals, but they also require calculation of gain and maintain a maximum and minimum full-scale range of ± 10V. Figure 2 displacement sensor input calibration module diagram Figure 3 shows the force, displacement sensor input calibration comparison chart. Figure 3 displacement sensor input calibration comparison chart First, study the force sensor input. The force sensor connected to the computer system is a Wheatstone bridge with an excitation voltage connected to it, which outputs a feedback signal in mV.3 The strength of this signal depends on the excitation voltage, for example 10 V , To be provided by a very accurate linear power supply (internal or external), the final output signal of the force sensor is proportional to the external force exerted on the force sensor, which is the force signal measured by the computer system. The second is to determine the sensitivity of the selected force sensor. Force sensor sensitivity is measured by the metrology department using a standard dynamometer and is indicated on the force sensor verification certificate. For example, the force sensor has a sensitivity of 1. 979 8 mV / V. Then determine the hardware gain. To get the best ADC resolution, this mV-level signal needs to be amplified by hardware gain to get the signal as close as possible to ± 10V over full scale. It is straightforward for the user to determine the first-order gain required for a particular force sensor, As listed in Table 1. For a force sensor with a defined sensitivity coefficient, the amplified signal voltage range can be calculated using the following formula: Amplified signal voltage = excitation voltage value × sensor sensitivity × amplification factor Each level of amplification factor has a corresponding ideal force sensor sensitivity, which is to give the maximum amplification that sensitivity. For example, the corresponding force sensor has an ideal sensitivity of 2 mV / V for 500 times the hardware gain. Best Value Electric Bike,Best Budget Electric Bike,Lectric Ebikes,3 Wheel Electric Bike Wu Xi Mdka New Energy Technology Co., Ltd. , https://www.evmdka.com