1.1.3　Measuring instruments

Measuring instruments refer to all instruments used for direct or indirect measurement of the measured quantity value.For example,balance,stopwatch,ammeter,voltmeter,power supply and so on.

Selection of measuring instruments:

(1)Choosing the appropriate measuring range.If the measured value exceeds the measuring range of the instrument,the instrument may be damaged;if the measuring range gets too wide for unapparent readings then errors might increase.(https://www.daowen.com)

(2)Selecting an instrument with an appropriate level of accuracy.Generally,when meeting the measurement requirements,select the instruments with a low level of accuracy in order to prolong the service life of the instruments with a high level of accuracy.

Measurements are made with the instrument as standard for comparison,which requires the accuracy of instruments.However,due to the different purposes of measurement,the requirements for the accuracy level of the instruments are also different.For example,the balance for weighing platinum is accurate to 0.001 g,while it does not matter if the error of weighing carbon comes at dozens of grams.