The Design Of Insulation Resistance Tester

Insulation resistance (IR) is an important index in a testing of the safety equipment requirement and also is one of major parameters in judging whether insulations are in good shape or stained on the surface. A general wetting, local severe wetting or penetrability flaw of devices can be detected by measuring IR. Original IR testers are mostly semi-mechanical megohmmeters of which a low accuracy, tow displayed digital and failure in a tractor serving several purposes limit the megohmmeters usage and hide dangers. In this system, a high frequency high voltage switching regulated power supply and a single chip computer controller are introduced to realize an automatic measuring, a wide range and a high accuracy. The new IR tester can meet the need of IR measuring in industry and agriculture.Firstly, this disquisition carries out a brief introduction on the domestic and international development situation as well as the technical background of IR tester, and then elaborates the major content of the research introduced in this disquisition. Secondly, by analyzing error sources, combining with the natures of high voltage (HV) and weak current in IR measuring, the scheme of a single-chip computer as a core and applying HV to measure current is devised. The single-chip computer collects and handles the digital value converted from measuring signal, achieves keyboard input and liquid crystal display (LCD), etc. The partition of applying HV to measure current is composed of the DC/DC converter (single end fly back topography) and voltage-multiplying rectifying circuit. The converter supplied with a 12V D.C. voltage can generate 500V/1000V/ 2000V/5000V four different HVs. The author analyses the operating principle of DC/DC converter as well as elaborating some particular problems to be noticed and corresponding method in the electrical and structural design. Furthermore, the HV produced from voltage-multiplying rectifying circuit is divided by the IR and another standard resistance connected with IR in series. The divided voltage signal is transmitted to the single-chip computer via voltage follower and A/D converter to be handled and displayed on LCD. In latter partition of this disquisition, design methods of software system and programs to handle some important signal are elaborated. The whole of software is programmed with C language and is divided into four parts, and they are: the model of LCD; the partition of keyboard handling; analog/digital conversion; the partition of data processing. Finally, a test through examples shows that the system can obtain satisfactory results.The main features of this system:...