Measuring the insulation resistance of electrical equipment, should be measured by mega-European table, the selection principle is mainly mega-European table test voltage level and range to meet the requirements of the Protocol, has a high dynamic measurement accuracy and anti-site interference ability, the use of safe and convenient, performance and price ratio, there are two types of pointers and numbers, should be noted when using, Pointer meter belongs to the category of analog instrumentation, it is composed of hand generator and magnetoelectric ratio table, there are 100V, 250V, 500V, 1000V, 2500V and other specifications, different voltage levels of Oupou are dependent on the rated voltage of the handshake generator, The rated voltage of the handshake generator at each voltage level is determined by the speed of the shake 120r/min. Although according to the measuring principle of the ratio table, when measuring the large resistance resistance such as insulation resistance, the deflection of the mega-European table pointer has little to do with the fluctuation of the voltage of the hand generator, but too much deviation from the rated measurement voltage will prevent the defects of the insulation from being reflected properly and affect the accurate measurement of the insulation resistance. Therefore, the speed of the handle is specified when the Mega European table is used and should be kept in (120±24) r/min.

Measuring the cost performance of the instrument, in addition to price factors should also consider the function of the instrument, it is best to choose the digital mega-European table, digital Mega Euro table cost-effective advantage has three points.

(i), a digital mega-European table can replace several needle-type meters, so that the price of digital instrumentation relative decline, for example, an Italian HT production of ISO1100 handheld insulation resistance tester has four measurement voltage 100V, 250V, 500V, 1000V, the purchase of a digital mega-European table, Equivalent to the purchase of several pointer mega-euro tables.

(b), the pointer mega-European table can not be used as short circuit or electrical continuity inspection, because the circuit is not good or not short circuit is two different concepts, the line insulation capacity is poor, does not indicate short circuit, and the circuit is short-circuited indicates that the insulation has been damaged or the line wiring error. Insulation should be measured with a mega-European table, and a ohm meter measurement is applied to the short circuit.

When measuring line insulation with a pointer mega-European table, its reading is "0", it is not necessarily short circuit, because the mega-European table can not read the value below the 100kω, at this time to be judged by the Ohm table, if the Ohm table rx1ω file to measure the resistance of several euros, it can be judged as a short circuit. However, the digital mega-euro table can be used as short-circuit or electrical continuity inspection, for example, when the ISO1100 model for low resistance testing, its resolution is 0.01ω, which in turn makes the relative price of digital instrumentation decline.

(c), in the production of measurement insulation resistance is often continuous, for example: three-phase five-wire busbar, each segment of the bus Groove insulation resistance measurement has interphase, phase and between the ground, and so on, at least to measure the eight or nine data above. If you use the ISO5000 Intelligent Insulation resistance tester, you can store 200 data and print the output, not only to eliminate manual errors, but also to save a lot of time.

如何使用兆欧表进行绝缘电阻的测试

测量电气设备的绝缘电阻，应采用兆欧表来测量，选用原则主要是兆欧表试验电压等级和量程范围要符合规程要求，有较高的动态测量准确度和抗现场干扰能力，使用安全方便，性能价格比好，有指针式和数字式两种，使用时应该注意，指针式仪表属于模拟仪表范畴，它是由手摇发电机与磁电系比率表所构成，有100V、250V、500V、1000V、2500V等多种规格，不同电压等级的兆欧表均取决于手摇发电机的额定电压，每一电压等级的手摇发电机的额定电压是以摇把120r/min的转速来确定的。虽然根据比率表的测量原理，在测量绝缘电阻等大阻值电阻时，兆欧表指针的偏转与手摇发电机电压的波动关系不大，但过多的偏离额定测量电压，会使绝缘的缺陷不能正常反映而影响绝缘电阻的准确测量。因此，兆欧表使用时规定了手柄的转速，并应保持在(120±24)r/min。

衡量仪器的性价比，除了价格因素外还应考虑仪器的功能，最好能选用数字式兆欧表，数字式兆欧表的性价比优势有三点。

（一）、一台数字式兆欧表可替代数台指针式仪表，使数字式仪表的价格相对下降，例如，一台意大利HT公司生产的ISO1100型手持式绝缘电阻测试仪有四档测量电压100V、250V、500V、1000V，购买一台数字式兆欧表，相当于购买几台指针式兆欧表。

（二）、指针式兆欧表不能用作短路或电气连续性检查，原因是无法读数，因为线路的绝缘好坏与线路是否短路是两个不同的概念，线路绝缘能力差，并不表示短路，而线路短路则表示绝缘已损坏或线路接线错误。绝缘好坏应该用兆欧表测量，是否短路则应用欧姆表测量。

当用指针式兆欧表测量线路绝缘，其读数为“0”时，不一定是短路，因为兆欧表无法读出100kΩ以下的值，此时要用欧姆表加以判别，若用欧姆表R×1Ω档测出电阻为几欧，则可判为短路。但数字式兆欧表可兼作短路或电气连续性检查，例如ISO1100型兆欧表用于低电阻测试时，其分辩率为0.01Ω，这一功能又使数字式仪表的相对价格下降。

(三)、在生产中测量绝缘电阻往往是连续的，例如:三相五线制母线槽，每段母线槽绝缘电阻的测量有相间、相和地间等，至少要测八、九个数据以上。如果采用ISO5000型智能绝缘电阻测试仪，可储存200个数据，并打印输出，不仅免除人工差错，还可以节约大量时间。