Analyse Data Of Measurement

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EXAMPLE OF MEASUREMENTS2/33

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At the end of this lesson, students should be able to:Read and use Micrometer screw gauge,

Vernier Calliper and meter rule .Describe inaccuracy and errors in

measurement.

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METRE RULE

Smallest division on a metre rule is 0.1 cm

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Answer:

Answer:

HOW TO USE METRE RULE

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The Vernier Callipers

This instrument may be used to measure outer dimensions of objects (using the main jaws), inside dimensions (using the smaller jaws at the top), and depths (using the stem).

Vernier calipers can measure length with an accuracy of up to 0.01 cm.

VERNIER CALLIPERS

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HOW TO USE AND READ VERNIER CALLIPERS

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HOW TO USE AND READ VERNIER CALLIPERS

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VERNIER CALIPPER WITH NO ZERO ERROR

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VERNIER CALIPPER WITH NO ZERO ERROR (READING 1)

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VERNIER CALIPPER WITH NEGATIVE ZERO ERROR

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VERNIER CALIPPER WITH NEGATIVE ZERO ERROR (READING 1)

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VERNIER CALIPPER WITH POSITIVE ZERO ERROR

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VERNIER CALIPPER WITH POSITIVE ZERO ERROR (READING 1)

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MICROMETER SCREW GAUGE A micrometer allows a measurement of the size of a body. It is one of the most accurate

mechanical devices in common use. The micrometer screw gauge can be used to measure very small lengths such as the

diameter of a wire or the thickness of a piece of paper as it can measure length accurately up to 0.01 mm.

Figure 5: Micrometer Screw Gauge

MICROMETER SCREW GAUGE A mirometer allows a measurement of the size of a body. It is one

of the most accurate mechanical devices in common use. A micrometer screw gauge can measure length accurately up to 0.01

mm.

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MICROMETER SCREW GAUGE WITH NO ZERO ERROR

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MICROMETER SCREW GAUGE WITH NO ZERO ERROR (READING 1)

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MICROMETER SCREW GAUGE WITH NEGATIVE ZERO ERROR

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MICROMETER SCREW GAUGE WITH NEGATIVE ZERO ERROR (READING 1)

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MICROMETER SCREW GAUGE WITH POSITIVE ZERO ERROR

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MICROMETER SCREW GAUGE WITH POSITIVE ZERO ERROR (READING 1)

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Inaccuracy and errors in measurement.

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Consistency

The consistency of a measuring instrument is its ability to register the same reading when a measurement is repeated.

A set of measurements are consistent if all the values are close to the mean value.

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The consistency of a measuring instrument can be improved by

eliminating parallax errors during measurement.

exercising greater care and effort when taking readings.

using an instrument which is not defective.

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Accuracy

Examples of Precision and Accuracy:

Low Accuracy High Precision

Examples of Precision and Accuracy:

High Accuracy Low Precision

Examples of Precision and Accuracy:

High Accuracy High Precision

Accuracy is the degree of how close a measured value is to the actual (true) value.

Precision is how close the measured values are to each other.

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Ways to improve the accuracy of a measurement:

a) Repeated readings are taken and the average value is calculated.b) Avoid parallax errors.c) Avoid zero errors.d) Use measuring instruments with a higher accuracy.

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The sensitivity of a measuring instrument is its ability to respond quickly to a small change in the value of a measurement.

Measuring Instruments

Sensitivity

Metre rule 0.1 cmVernier callipers 0.01 cmMicrometerscrew gauge

0.001 cm

Wrist watch 1 sAnalogue stopwatch 0.1 sDigital stopwatch 0.01 sAmmeter 0.1 AMiliammeter 1 mA

Sensitivity

The smaller the minimum scale division, the more sensitive is the measuring instrument.

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The difference between the real value and the observed value.

ERROR

There are two main types of errors, that is

a) Systematics error

b) Random error

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SYSTEMATIC ERRORA systematic error is an error in reading the scale when a physical

quantity is being measured. It caused by the instrument, observer

and surroundings.

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Causes of a systematic error:a) A zero error occurs when the reading shown on the instrument is not

zero while the true reading is zero.

b) An error is caused when there is a flaw in the instrument. For example,

the edge of a ruler which is worn out causes an error in the measurement

of a length.

c) An error is caused by a wrong assumption.

d) Slow reaction when using an instrument causes an error. For example,

there may be a delay in pressing a stop watch.

e) An error caused by incorrect calibration of instruments.

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RANDOM ERROR

1) A random error is an error is an error which occurs when

the observer is reading the scale on the measuring instrument.

2) A reading obtained when a random error occurs can be

bigger or smaller than the true value, a positive or negative

error may occur.

3) A random error can be reduced by taking the measurement

of a physical quantity more than once and finding the average

reading.

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Examples of random errors are:

a)parallax error or error of measurement when a

reading is taken from unsuitable position relative

to the scale.

b)error in the reading of the scale.

c)error due to a change in temperature as the

experiment is being carried out.

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Author:

BADARIAH BT MANAB

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