Least count of screw gauge in cm

The simplest method measuring the length of a straight line is by means of a meter scale. But there exists some limitation in the accuracy of the result: (i) the dividing lines have a finite thickness. (ii) naked eye cannot correctly estimate less than 0.5 mm For greater accuracy , devices like (a) Vernier callipers (b) micrometer scales (screw gauge) are used . Vernier Caliper : It consists of a main scale graduated in cm/mm over which an auxiliary scale (or Vernier scale) can slide along the length. The division of the Vernier scale being either slightly longer and shorter than the divisions of the main scale. Least count of Vernier Callipers The least count or Vernier constant (v.c.) is the minimum value of correct estimation of length without eye estimation. If N division of vernier coincides with (N-1) division of main scale, then $\displaystyle N \; VSD = (N-1) MSD $ $\displaystyle 1 \; VSD = \frac $

Table of Contents • • • • • What is least count of screw gauge in CM? The minimum the value of the least count of a device, the accurate is it’s measurement. The least count of screw-gauge is 0.01 means it is 100 times more accurate than a meter scale. Now, zero if zero error is +0.005cm means when the mark is at zero, the actual reading is 0.005cm at that time. What is the least count of vernier caliper and screw gauge? The least count of the screw gauge is 0.01 cm and the least count of a vernier caliper is 0.001 cm. Is the screw gauge with smaller least count always better? A screw gauge having a smaller value of pitch has greater accuracy. What is least count of pressure gauge? Pressure which is measured in minimum of perticular pressure gauge called its least counts. Suppose in a pressure gauge range 0-6 is devided in to equally 6 parts for each 1 kg/sq cm and 1 parts devided in to itself by 10 division for each 1 kg/sq cm. How can the least count of a screw gauge be decreased? The least count of a screw gauge can be decreased by increasing the pitch and decreasing the total number of divisions on the circular scale . What is least count of weighing balance? Some manufacturers direct in their operating manual to weigh minimum 1.0 mg on balance having 0.01 mg least count i.e. least count X 100. But the thumb rule followed in pharmaceutical industries for lower limit is least count X 50 and the upper limit is 80% of the capacity of the balance. How can the least count o...

Fig. 1 Screw Gauge Pitch of the screw It is defined as the linear distance moved by the screw forward or backward when one complete rotation is given to the circular cap. Least Count of the Screw Gauge The Least count (LC) is the distance moved by the tip of the screw, when the screw is turned through 1 division of the head scale. Reading of a Screw Gauge Fig. 2 Screw Gauge Diagram Consider figure 2. Place a wire between A and B, the edge of the cap lies ahead of N th division of linear scale. Then Linear scale reading (LSR) = N If n th division of circular scale lies over reference line, then Circular scale reading (CSR) = n × (LC) Total reading (or observed reading) = LSR + CSR = N + n × (LC) Zero error When the two studs A and B of the screw gauge are brought in contact and if the zero of the circular scale does not coincide with the reference line then the screw gauge has an zero error. 1. Positive zero error Zero error is said to be positive if the zero of the circular scale lies below the reference line as shown in figure 3. Here , zero error = + (n × LC) Here, n= division number on circular scale coincide with reference line. zero correction (C) = negative of zero error C = – zero error = – (n × LC) Therefore, True reading = observed reading + zero correction = observed reading – (n × LC) Fig. 3 According to above figure, n = 2 zero error = + (n × LC) = + (2 × LC) 2. Negative zero error Zero error is said to be negative if the zero of the circular scale lies above t...

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