The Development Of High-precision Gas-sensor Properties Testing System

With the rapid development of gas-sensors, gas-sensor technology has developed a major breakthrough, but at present the complete test system for gas sensors and gas sensors do not keep up with the pace of developing technology, which pairs the development of gas sensors has brought greatly affected. This system builds on the current market and research laboratory test system for gas sensors based on the combination of the latest DC weak signals data acquisition technology, and novel capacitor Development of key controls and portable devices, set up a new laboratory Gas sensor test system. System Application of high-precision DC weak signals acquisition and multi-channel testing technology, and established the basis of the simulation with high simulation testing environment, portability and capacitive buttons. Not only improve the test efficiency, but also to improve the measurement accuracy, so that most enterprises and research institutions to meet the gas sensor testing laboratory needs, and can be applied in accordance with its own features to personalize the settings.The measurement system was a total simulated testing environment, data acquisition hardware and capacitive buttons control system composed of three parts.Simulated testing environment simulated by the testing environment, gas tank and heating, temperature control hardware circuit. MCH metal ceramic heating elements heat the material as a testing environment, MCH metal ceramic heating elements heat up fast, its surface temperature can be quickly reached in 20-30 seconds, hundreds of degrees, the maximum surface temperature can reach about 800℃. In the normal working hours, the temperature compensation quickly, its insulation. And because its operating voltage can be free to choose the characteristics of the system to facilitate consistency of Development. After the heating element in the selection, we use the J-type thermocouple on the temperature measurements accurate to use AD549A Zuowei thermocouple signal conditioner, increased circuit integration, and integration of the freezing point as AD549A reference source and Yu calibration amplifier can be directly connected with the thermocouple, with strong output capability (0℃-300℃between the output of 10mV /℃), and therefore no additional precision amplifier. Can be achieved on the thermoelectric power of the compensation amplifier, and because of its own manufacturing process can achieve 0℃-300℃range of linear amplification, so that can achieve high accuracy temperature measurement, test results show that the accuracy can be achieved within±1℃. Location of the fan through the improvement, it has good heat capacity, can shorten the test cycle, the gas sensors to improve the accuracy of laboratory testing and save the test of time.Data acquisition hardware mainly achieved through constant source of small precision DC signal acquisition, divided into high-precision small DC signal acquisition system, analog-digital conversion system of two parts. High-precision small DC signal acquisition system used by AD8608 and ADG708 achieve automatic shift and large dynamic range detection, compared to a general amplification system can automatically shift fast and high-precision detection circuit switching method to avoid the traditional gain disadvantages, to achieve a small error in the high-precision amplifier, a practical application value. AD8608 gain additional resistors of different resistance, while the ADG708 is responsible for ADG8608 quad op amp integrated strobe, gain resistance test range according to the optional 20?, 100?, 900?, 9K?, 90K?, 900K?, 4.5M?, any of the four as the combination (0.1% accuracy are high-precision resistor). In its back-end and A / D converter input voltage set up between the access TLV2252 follower (input impedance high and low output impedance) to reduce signal loss also play a buffer role, connecting link. ADC back-end system, the chosen ofΣ-ΔA / D converter AD7705 as the A / D converter, a large part of the reason is because of the need of its built-PGA as a signal of the second amplification, and it has high-precision. The test is Developmented to be smaller by more than measurement error.Capacitive key-press controller button by touching a piece of metal electrodes materials (the metal sensors on PCB) to achieve. MCU detected by changes in capacitance, we can detect this small change, to achieve capacitive buttons. The DC weak signals amplification circuit Developmented for the high-precision DC small signal amplification provides a reference, capacitive key systems for future system Development provides a new control scheme. Meet the general needs of the test gas sensor has a certain practical value.