Measurement of Length (Direct Method)
Description:
For the measurement of length we have number of techniques, which are broadly divided into two main groups −
- Direct Method
- Indirect Method
Direct Method
When we can reach both the ends of length, the measurement is done by direct method. In direct method instruments used are meter scale, Vernier calliper, screw gauge / spterometer.
Meter Scale
Meter scale is an instrument that has numeric calibrations on it to measure length. The precision / least count of meter scale is 1mm i.e. measurement with accuracy till 1 decimal point is only available.
Example − Meter scale can measure length of 21.6cm or 21.7cm, but it is unable to measure a length between the two.
Vernier Calliper
Vernier calliper is a measuring device that has better least count i.e. it is more accurate that the meter scale. It has the least count of 0.1mm.
Example − Vernier calliper can measure length of 21.65cm or 21.66cm
Screw guage
Screw gauge is a measuring device that uses the concept of pitch and circular scale. Least count of screw gauge is given by −
Least count = pitchno. of divisions of circular scale
Example – Screw gauge can measure length of 21.654cm or 21.655cm