Vernier scales

Nonius, m. ipl. Nonien) vernier, -einteilung,/. vernier scale. 

Ca and Cg) for simplicity. In this case two types of vernier structure are considered as shown in Fig. 2.32. Structure [a] is composed of A- and B-planes, which are stacked alternatively along the h-axis as. .. ABAB. .. Due to the difference between the dimensions of the unit cells of each plane, the unit length of the supercell structure along the c-axis is expressed by eqn (2.7). In structure [b], the structures A and B are mutually interpenetrated. The dimension of the super structure along the c-axis is also expressed by eqn (2.7). In each case, the relation between structures A and B is very similar to that between the main scale and vernier scale in vernier calipers. 

Suppose the measurements are repeated with a caliper whose vernier scale permits careful measurement to the nearest 0.01 cm and estimation to the... 

The angle is read off a vernier scale on the control knob. This procedure is repeated several times and an average value is calculated. This value is converted to an o.p.d. value using Eq. (1). The coverslip is then removed and the ethanol allowed to evaporate. The section is remounted in glycerol and the same point on the same section is remeasured. Refractive index can be calculated using Eq. (2) where Nj and N2 are 1.362 and 1.474 for ethanol and glycerol, respectively. All measurements are made at 20°C unless otherwise stated. 

FIG. 2.1. (Left) (a) Vernier scale set at a reading 3.45 cm. (b) A typical Vernier caliper gauge, (c) Shows the coixect angle for accurate measurement of tube diameters, (d) An incoirect angle, which will result in enors of measurement. 

Say 10 Vernier scale = 9 main scale division 1 Vernier scale = 9/10 main scale division Vernier constant (V. C) = (1 - 9/10) mm = 0.1 mm = 0.01 cm To determine the diameter record readings in the form of table shown helow. 

Main scale reading (cm) Vernier scale division (V.D.) Vernier reading (V.D X V.C) cm Total reading = diameter (d) cm... 

Ver-nier Scale Sight. (Riflt.) A hind Slight with a vernier scale for accurate aojostment. The peep-sight is elevated or depressed by a screw the scale on the bar of the sight being slotted. 

Some pipet volumes are altered using a vernier scale. Follow the instructions provided by the manufacturer. Generally these are not recommended because it is easier to make mistakes with them, and the scale tends to wear. Multichannel pipets are designed to deliver 4, 8, or 12 vol simultaneously, and therefore are ideal for microtiter plates. The pipets having 12 channels offer highest flexibility in that up to 12 channels can be utilized. Any number of the channels can be loaded with a tip (up to 12). This fact often confuses workers when they first encounter such pipets. Practice the pipetting action and putting on tips. 

All instruments employing a vernier consist of two scales one moving and one fixed. The fixed scale is graduated in millimetres, every 10 divisions equalling 10 mm, and is numbered 0, 1, 2, 3, 4 up to the capacity of the instrument The moving or vernier scale is divided into 50 equal parts which occupy the same length as 49 divisions or 49 mm on the fixed scale (see Fig. 6.1). This means that the distance between each graduation on the vernier scale is 50 mm=0.98 mm, or 0.02 mm less than each division on the fixed scale (see Fig. 6.2(a)). 

If the two scales initially have their zeros in line and the vernier scale is then moved so that its first graduation is lined up with a graduation on the fixed scale, the zero on the vernier scale will have moved 0.02 mm (Fig. 6.2(b)). If the second graduation is lined up, the zero on the vernier scale will have moved 0.04 mm (Fig. 6.2(c)) and so on. If graduation 50 is lined up, the zero will have moved 50 x 0.02 = 1 mm. 

Since each division on the vernier scale represents 0.02 mm, five divisions represent 5 x 0.02 = 0.1mm. Every fifth division on this scale is marked 1 representing 0.1 mm, 2 representing 0.2mm and so on (Fig. 6.1). 

To take a reading, note how many millimetres the zero on the vernier scale is from zero on the fixed scale. Then note the number of divisions on the vernier scale from zero to a line which exactly coincides with a line on the fixed scale. 

In the reading shown in Fig. 6.3(a) the vernier scale has moved 40 mm to the right. The eleventh line coincides with a line on the fixed scale, therefore 11 x 0.02 = 0.22 mm is added to the reading on the fixed scale, giving a total reading of 40.22 mm. 

The above principles apply to the vernier height gauge, Fig. 6.9. In this case the beam, carrying the fixed scale, is attached to a heavy base. The vernier scale carries a jaw upon which various attachments can be clamped. It is most widely used with a chisel-pointed scribing blade for accurate marking out, as well as for checking... 

As well as linear measurement, vernier scales can equally well be used to determine angular measurement. 

Since each division on the vernier scale represents 5 minutes, the sixth graduation is numbered to represent 30 minutes and the twelfth to represent 60 minutes. 

The stock of the vernier protractor carries the fixed scale. The removable blade is attached to the moving or vernier scale, which has a central screw to lock the scale at any desired position and give angular measurement to an accuracy of 5 minutes. 

Since the vernier scale can be rotated in both directions, the fixed scale is graduated from 0-90,90-0,0-90,90-0 through 360°. This requires a vernier scale for each, and therefore the vernier scale is also numbered 0-60 in each direction. 

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