Vernier instruments

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). 

Copyright 2010 Bruce J. Black. E bllshedby Elsevier Ltd. All rights of reproduction in any form reserved 

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. 

Many of the electronic measuring instruments outlined in this chapter, e.g. vernier calipers, micrometers and dial test indicators, can be equipped to output data either through available data cables or by wireless transmitters/receivers. This data can be printed out or sent to a computer and collected and used by quality control to provide statistical information or for the generation of inspection certificates. 

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The measurement of angles can be simply carried out by using a protractor, but the degree of accuracy obtainable is, at best, 5 minutes using a vernier instrument. Greater accuracy can be obtained by using a sine bar in conjunction with gauge blocks. 

Fein-messen, n. precision measurement, -mes-ser, m. micrometer vernier, -messgerat, n. precision measuring instrument, -messlehre, /. micrometer caliper or gage, -mess-... 

The thickness of the plate Q is such that when the vernier is at zero the right and left halves of the field in the eye-piece appear equally intensely illuminated. Before, however, the. instrument is used, it must be ascertained that the two halves are really equally bright when the vernier is at zero if this is not the case, there is a displacement of the zero, which may be corrected by means of a regulating screw. When this has been done, the tube T of exactly determined length closed at the ends with two glass plates and containing the solution to be examined, is interposed, If the liquid... 

The very hard materials can be checked using the standard pressure settings. For softer materials, this will cause undue distortions. The micrometer or vernier calipers need to be gently passed over the item. The faces of the instrument must just touch the surface. This can be felt through the instrument as a very mild resistance. The measurements will represent the high points on the surface. 

Nowadays many digital instruments can be obtained cheaply on the Internet. These can often be coupled to a computer, allowing real-time registration. You might have a look at www.vernier.com, but there are other sites. 

This instrument will be graduated in centimeters and millimeters. In its simplest form there will be a sliding scale, 9 mm long, divided into 10 equal parts. Thus the difference between a scale division and a vernier division is one-tenth... 

Ti and Tt. The verniers wall of the instrument, while two others, Ni and N, are attached to T3 and Tz and move with it. The double scales (divided into millimeters) which move with containers Tz and Tz serve with the aid of the vernier readings to determine the heights of a liquid column, and permit these heights to be read after the colors on both sides have been equalized. 

The manipulation of the instrument is described below. First of all, containers Tz and Tz are lowered by means of a knob (not shown in Fig. 16) until they touch the bottom of cups Ti and Ti. By so doing, the zero readings of the verniers Nz and Nz are brought opposite the zero marks of the scales Sz and Sz - Cups Tz and Tz are raised until the position of the verniers Ni and Ni with respect to scales Si and Si shows the desired total height of liquid (identical on both sides). Usually a column of 100 mm. is taken, and containers Tz and Tz are fixed in this position by means of lock screws. It is now possible, simply by moving Tz or Tz upward, to divide the total 100 mm. depth of the liquid at will between one of cylin-... 

A modern scanning electron microscope, with vernier, is also an excellent instrument to measure dry state (approximately 0% RH) diameter of human hair fibers. 

The barometer is perhaps the simplest pressure gauge and it is stili commonly found in laboratories to assess barometric pressure. It is one of the few instruments that measures absolute pressure. Before Toricelli, water columns of 10.3 m were necessary to study pressure. Toricelli invented the mercury barometer with a density 13.6 times that of water thus the column height is never much more than 0.9 m. The barometer is composed of a tube, a pool of mercury as well as a scale to measure distance and a vernier used to assess the exact position on the scale to a precision of 0.1 mm. 

The most common instrument using the above principle is the vernier caliper (see Fig. 6.4). These instruments are capable of external, internal, step and depth measurements (Fig. 6.5) and are available in a range of measuring capacities from 150 mm to 1000 mm. 

Vernier calipers Large measuring range on one instrument. Capable of internal, external, step and depth measurements. Resolution of LCD model 0.01 mm... 

Operators require fewer skills. Many operator jobs consist mainly of minding a machine, especially now that more and more processes are automated. However, some operators may have to 45 check components produced by their machines to ensure they are accurate. They may require training in the use of instruments such as micrometers, verniers, or simple go/no go gauges. 

Vernier calipers Large measuring range on one instrument. Capable of internal, external, step and depth measurements. Resolution of LCD model 0.01 mm Resolution 0.02 mm. Point of measuring contact not in line with adjusting nut (Abbe s principle). Jaws can spring. Lack of feel. Length of jaws limits measurement to short distance from end of workpiece. No adjustment for wear... 

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