Study On Minitype-Digital Capacitance Micrometer

As an important method of non-contact micro displacement precision measurement, capacitance micrometers have been widely used in this domain. But, with the development of the industry system, the traditional capacitance micrometers can't meet the requirements in some kind of applications, because of its high power consumption and huge volume.To avoid the disadvantages of the traditional capacitance micrometers, the paper uses the method of digital Minitype instrument designing, and develops a whole new type of capacitance micrometer. Finally, a sample is presented.The new type of capacitance micrometer is controlled by a MSP430 micro-controller; the control circuit has a small volume of 130×100×40(mm~3). The maximum power consumption is smaller than 0.13W, with a source of 3 AA batteries the system can work continually for 7 days. The output of the sensor is serial signal, with normal shield cable the signal can be transmitted more than 30 meters. When the system carries on a differential measurement mode with two sensors ofΦ3.5mm core diameter, it can achieve timing drift of smaller than 10nm/h, and the resolution is 10nm, measuring range is±80μm, the distance between zero-position and the sensor's measuring plate is90μm, the linearity is better than 0 .2%. The main works in the dissertation includes the following aspects:1. A new model of Minitype-digital capacitance micrometer is presented based on the study of the traditional capacitance micrometer.2. Explains the method of designing the dimension of new type of sensor. Provide a basis for designing a series of sensors.3. The relationship between capacitance and measuring distance is non-linearity, a curve fitting method is presented. And the method meets the precision requirement.4. By optimized design such as the choice of low power consumption device and computer interface, the instrument can be handled easily and be carried conveniently.The creative works are as follows:1. Introduces the capacitance measuring chips to the capacitance sensor. Employs digital cable instead of analog driven cable or non-complete driven cable. Overcomes the weakness of the traditional sensor's signal transmission capability. Makes the system has powerful ant jamming ability. The drift is restrained efficiently.2. Achieved a minimum volume of the whole system by integrating the measuring circuit into the sensor. If there is no need to display the result locally, the whole system is only made up of sensors and a control computer. The system can adapt to multi-channel measurement and heavy density monitoring. Pre-warming-up is not necessary. The system can be used immediately after power on.3. Presents a method of reducing the temperature drift of the capacitance micrometers. The method reduces 60% of the temperature drift. A series of experiments have proved its fine performance.