Specify the use of measuring instruments and measuring methods, compare the standard values used for judgment, and the values measured each time may be different.
Chinese name
Measuring tools
Definition
About the use of measuring instruments ・ measuring methods
Measurement refers to measuring the shape and size of objectsMeasuring instrumentAnd device to measure and quantify.
Inspection refers to comparing the measured result (value) of an object with the standard value used to determine whether the object is qualified.
About measurement error
When measuring the shape and size of an object, there will be differences between the actual value and the measured value or the approximate value. In addition, even under the same conditions, the value measured each time may be different. This is measurement error.
Measurement errors can be roughly divided into errors caused by the measurer, measurement errors, errors caused by external conditions, accidental errors, etc.
When reading the measured value, the error caused by the character and tendency of the measurer can also be said to be the error caused by the measurement ability of the measurer and the difference in the sense of measurement.
② Measurement error
The error caused by the structure of the measuring instrument, the change of friction, measuring pressure, etc., and the failure to adjust the mechanism of each part.
③ Errors caused by external conditions
The error caused by the change of measurement environment such as room temperature, humidity, illumination, vibration, etc.
④ Accidental error
Errors caused by interaction of various uncertain small factors under certain conditions.
Precautions for use of measuring instruments
① Select the measuring instrument that matches the measurement content.
Measuring instruments of different specifications and models have different measuring methods, measuring ranges, accuracy, etc., so it is necessary to select measuring instruments of appropriate specifications and models.
② Use carefully.
The measuring instrument is an instrument with precise structure, so it should be careful not to drop it from a high place, or be squeezed, vibrated or collided.
③ Always keep clean when using.
Pay attention to clearingMeasuring surface, sliding surfaceTo prevent rust.
④ To measure a stationary object.
If the moving object is measured, the measuring instrument will be damaged and the correct measurement cannot be carried out.
⑤ The error caused by parallax shall be considered.
Since the position of the eyes is different when reading the scale, it will cause great errors, so it is necessary to read the scale from the top.
⑥ The instrument must be checked at the beginning of measurement.
Check the measuring surface, sliding surface and zero point position.
⑦ Pay attention to measuring at standard temperature.
It is necessary to consider that the size of the measured object will change due to temperature changes, and the error caused by temperature changes should be considered.
⑧ Pay attention to the wear of the measuring surface.
Pay attention that the measuring surface and sliding surface are easy to wear due to contact.
⑨ Correct regularly.
In order to measure stably, it is necessary to calibrate and confirm the accuracy regularly.
⑩ It should be kept in a place with little environmental change.
Vernier calipers (Mosel type) can be used for external measurement, internal measurement and depth measurement, and are generally used for objects with a measurement accuracy of 1/10~1/20mm.
2. Reading method of vernier caliper (scale)
① Read the scale of the ruler body (15+α mm) when it coincides with the scale of the vernier at 0 °.
② Read the scale of the vernier (3 × 1/10mm) when the scale of the ruler body coincides with the scale of the vernier.
L=（15+α）=15+0.3=15.3mm
Precautions for use
① Clean the sliding part of the vernier caliper before use.
② Clean the measuring surface of the vernier caliper before use.
③ When measuring, try to measure near the ruler body.
④ Do not apply unnecessary measuring pressure to the vernier caliper.
⑤ Make the measuring surface contact the measured object correctly.
⑥ Wipe it thoroughly after use, and do not let garbage enter the slide rail.
⑦ After use, check whether each part is damaged, and correct any impact marks.
