电表的改装与校正实验报告.doc

电表的改装与校正实验报告 实验四 电表的改装和校准 实验目的 1(掌握电表扩大量程的原理和方法; 2(能够对电表进行改装和校正; 3(理解电表准确度等级的含义。 实验仪器: 微安表，滑线变阻器，电阻箱，直流稳压电源，毫安表，伏特表，开关等。 实验原理: 常用的直流电流表和直流电压表都有一个共同部分，即表头。表头通常是磁电式微安表。根据分流和分压原理，将表头并联或串联适当阻值的电阻，即可改装成所需量程的电流表或电压表。 一 将微安表改装成电流表 微安表的量程I很小，在实际应用中，若测量较大的电流，g 就必须扩大量程。扩大量程的方法是在微安表的两端并联一分流电阻R。如图1 所示，这样就使大部分被测电流从分流电阻上流S 过，而通过微安表的电流不超过原来的量程。 设微安表的量程为I，内阻为R，改装后的量程为I，由图1，gg 根据欧姆定律可得， (I - I)R= IR gggS IRgg R= SI,Ig 设n = I /I, 则 g Rg R= (1) Sn,1 of induction welder should hold the appropriate qualifications. (4) the laying of 1) grounding wire welding should be used, length and quality of the weld seam construction drawings shall meet requirements and GB50169 provisions after welding the welds and welds should be cleaned, and painted anti-corrosion coatings. Where the extension leads from the grounding should be clearly marked, and decay and break-proof measures of protection. 1) ground wire through the settlement joints or telescopic ... Cabling and wiring in accordance with the relevant requirements. Cable manufacturers representatives under the direction of head, testing, dedicated connections, secondary circuit grounding bolts, control cable grounding of the shield as designed. Construction of cable fireproof plugging the complete Panel, Cabinet hole. 9.6. quality inspection and acceptance (1) steel pipe inspection and acceptance of materials required for pipe installation, welding materials, related connectors and coating material shall be carried out according to this chapter, section 10.2 inspection and acceptance. (2) inspection and acceptance of installation quality of steel 1) steel pipe during the installation process, should in conjunction with 由上式可见，要想将微安表的量程扩大原来量程的n倍，那么只 Rg须在表头上并联一个分流电阻，其电阻值为R= 。 Sn,1 图1 图2 二 将微安表改装成电压表 R，我们知道，微安表虽然可以测量电压，但是它的量程为Igg是很低的。在实际应用中，为了能测量较高的电压，在微安表上串联一个附加电阻R，如图2所示，这样就可使大部分电压降在H 串联附加电阻上，而微安表上的电压降很小，仍不超过原来的电压量程IR。 gg 设微安表的量程为I，内阻为R，欲改装电压表的量程为U，gg 由图2，根据欧姆定律可得， I(R+ R)=U ggH U, R = R (2) gHIg 三 改装表的校准 改装后的电表必须经过校准方可使用。改装后的电流表