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电学实验中仪器的选择是一项综合性指标,既要对仪器不造成损害,又要使测量的误差尽可能的小,并不是量程不小于待测量值和实际值不大于额定值即可。怎样选择仪器呢? 一、电表的选择指针式电压表、电流表的“允差”(最大可能误差)为±(量程×等级÷100),例如某一2.5级电压表量程0～3伏,允差ΔU=±3×2.5％=±0.075伏。因此,用同一量程时,电表不同示数的绝对误差相同,但相对误差不同。当上述电压表读数U=2.5伏时,则相对误差仍为ΔU/U=±0.075/2.5=±3％,而当读数U=0.50伏时、相对误差却增大为ΔU/U=±0.075/0.50=±15％。由此可见,选择电表量程时,应使指针的偏
The choice of instrument in electrical experiment is a comprehensive index, which should not cause damage to the instrument, but also make the measurement error as small as possible. It is not that the range is not less than the value to be measured and the actual value is not greater than the rated value. . How to choose the instrument? First, the meter’s choice indicator voltmeter, ammeter’s “tolerance” (the maximum possible error) is ± (range × grade ÷100), for example, a 2.5 voltmeter range 0 ~ 3 volts, allow The difference ΔU=±3×2.5%=±0.075 volts. Therefore, when using the same range, the absolute error of the different readings of the meter is the same, but the relative error is different. When the above voltmeter reading U = 2.5 volts, the relative error is still ΔU/U = ± 0.075/2.5 = ± 3%, and when reading U = 0.50 volts, the relative error increases to ΔU/U = ± 0.075 /0.50=±15%. It can be seen that when selecting the meter range, the pointer should be biased