Date post: | 14-Apr-2018 |
Category: |
Documents |
Upload: | anonymous-0ys8o5xr |
View: | 255 times |
Download: | 0 times |
of 19
7/27/2019 Vernier callipers
1/19
1.4 UNDERSTANDING
MEASUREMENTS
Students should be able to:
1. Measure physical quantities using appropriateinstruments.
2. Explain sensitivity.
3. Explain accuracy and consistency.4. Explain types of experimental error.
5. Use appropriate techniques to reduce errors.
7/27/2019 Vernier callipers
2/19
Measuring Instruments
7/27/2019 Vernier callipers
3/19
Estimation of Dimensions
Suitable instruments are required to make the
measurement;- more reliable,
- better accuracy,
- more consistency.
7/27/2019 Vernier callipers
4/19
Sensitivity
Definition: the capability of an instrumentto respond to physical stimuli or to registersmall physical amounts or differences.
A sensitive instrument can; Detect small changes in a quantity measured,
React very fast to the changes inmeasurements made.
Instrument with smaller divisions on thescale are more sensitive.
7/27/2019 Vernier callipers
5/19
Precision
Definision : the degree of uniformity or
reproducibility of the measurements.
7/27/2019 Vernier callipers
6/19
The Vernier Scales
7/27/2019 Vernier callipers
7/19
Introduction
The precision of length measurements maybe increased by using a device that uses asliding vernier scale.
Two such instruments that you will use tomeasure lengths of objects are: vernier callipers
micrometer screw gauge.
These instruments have: a main scale (in millimetres)
a sliding or rotating vernier scale.
7/27/2019 Vernier callipers
8/19
Explanation
In figure below, the vernier scale (below) is dividedinto 10 equal divisions.
Vernier scale reading is the mark on the vernierscale which exactly coincides with a mark on themain scale (0.7 mm).
The reading = 3.0 +0.7 = 3.7 mm.
7/27/2019 Vernier callipers
9/19
Reading = 15.0+0.8 = 15.8 mm
7/27/2019 Vernier callipers
10/19
The vernier calipers
Vernier calipers allows readings to the nearest 0.02mm.
This instrument may be used to measure outer dimensions of objects (using the main jaws),
inside dimensions (using the smaller jaws at the top),
depths (using the stem).
7/27/2019 Vernier callipers
11/19
Example
37mm 0.46mm 37.46mm+ =
7/27/2019 Vernier callipers
12/19
34 mm 0.60 mm 34.60mm+ =
7/27/2019 Vernier callipers
13/19
40mm 0.00mm 40.00 mm+ =
7/27/2019 Vernier callipers
14/19
Micrometer Screw Gauge
A screw with an accurately constant pitch (theamount by which the thimble moves forward or
backward for one complete revolution).
A pitch = 0.50 mm
2 full turns are required to close the jaws by 1.00 mm.
The rotating thimble is subdivided into 50 equal
divisions.
The thimble passes through a frame that carriesa millimetre scale graduated to 0.5 mm.
While doing the measurement, the manufacturer
recommends 3 cl icksof the ratchet before
taking the reading.
7/27/2019 Vernier callipers
15/19
7/27/2019 Vernier callipers
16/19
Example
7mm 0.38 mm 7.38mm+ =
7/27/2019 Vernier callipers
17/19
7.5mm 0.22 mm 7.72mm+ =
7/27/2019 Vernier callipers
18/19
3 mm 0.46mm 3.46mm+ =
7/27/2019 Vernier callipers
19/19
3.5 mm 0.06mm 3.56mm+ =