Traveling microscope

We saw in Section 6.2 that the Wilhelmy plate offers an accurate method for measuring 7 cos 6. We thus have one experiment with two unknowns. The Wilhelmy balance measures the weight of the meniscus in this section we examine the height to which the meniscus climbs on the same surface. We shall see that this distance — which may be accurately measured with a traveling microscope or cathetometer — also depends on 7 and 6. The functional relationship between these parameters and the experimental variables is different from the case of the meniscus weight. Therefore we have two experiments with two unknowns that can be solved for 7 and 6. 

Dimensions such as the width of a dumb-bell or the depth of a nick in a tear specimen will be less than 30 mm but could not be measured with a dial gauge. Because of the virtual impossibility of applying a known pressure, such measurements must be made in an essentially contactless manner. For low precision, calipers or a rule may suffice but for readings to 0.01 mm a travelling microscope or projection microscope is most suitable, and this is specified in ISO 23529 Method D and applies also to dimensions over 30mm. Projection microscopes also find use in examining profiles and for rapid swelling tests (see Chapter 16, Section 2.1). 

Methods B and C are the same as ISO 23529 plus, optionally, a tape for measuring circumference up to 100 mm. Method D only mentions a traveling microscope and requires an accuracy of 0.005 mm. It says that this method is more accurate than method A but more time consuming - in... 

The area of a polished electrode (taken to be the projected or geometric area in most voltammetric experiments at times > 1 s) usually is measured directly or electrochemically. If the electrode is of regular geometry, such as a disk, sphere, or wire of uniform diameter, its characteristic dimensions can be measured by use of a micrometer, optical comparator, or traveling microscope and the area calculated. 

The same method in principle can be used with thin wires, or single textile fibres, if a microscope (preferably a travelling microscope) is used for inspection of the liquid surface. Adam and Shute2 have studied contact angles with one, or with two, liquids and solid fibres, finding that the accuracy is almost equal to that obtainable by the plate method. 

The kinetics of the craze growth process during RCG, as observed by Rimnac et al. on the specimen surface using a travelling microscope, was described... 

Fig. 4.23. Craze growth in plasticized PVC (6% DOP) during RCG characterized by relative craze length s/s versus relative cycle number N/N as measured by travelling microscope and by interference optics...

As the boundary moved down the U-tube, the resistance of the solution increased the galvanometer deflection was kept constant by decreasing the variable resistances. The movement of the boundary was followed with a travelling microscope, and the time taken to reach successive graduations was recorded on a stop-watch. Immediately after the experiment the galvanometer was calibrated to get an accurate value of the current used. The measurements and results are tabulated below. 

Fig. 6 Delamination in a specimen with unidirectional lay-up as seen through the travelling microscope. On this scale, slight deviations from the mid-plane are observed, the black vertical lines are each 1 mm apart.

Later, Neumann developed the static Wilhelmy plate method which depends on capillary rise on a vertical wall, to measure 6 precisely. A Wilhelmy plate whose surface is coated with the solid substrate is partially immersed in the testing liquid, and the height of the meniscus due to the capillary rise at the wall of the vertical plate is measured precisely by means of a traveling microscope or cathetometer. If the surface tension or the capillary constant of the testing liquid is known, then the contact angle is calculated from the equation, which is derived from the Young-Laplace equation... 

A relatively simple technique provided there is reasonable access to the deposit, is to measure the thickness. Using a removable coupon or plate the thickness of a hard deposit such as a scale, may be made by the use of a micrometer or travelling microscope. For a deformable deposit containing a large proportion of water, e.g. a biofilm it is possible to use an electrical conductivity technique as described by Harty and Bott [1981], Fig. 17.11 illustrates the principle. The instrument consists of a steel needle mounted on a micrometer which forms part of... 

The thickness of the specimen was measured with a digital micrometer its width was measured with a 50x traveling microscope. The digital micrometer and the traveling microscope were accurate to 0.0025 mm. These measurements were made at five cross-sections spaced 30 mm apart and centered about the midpoint of the 127-mm g e length between the two grips. The cross-sectional area is the product of thickness and width. The smallest of the five areas was used to calculate the stress for the stress-strain curves. Table 1 lists the mean and coefficient of variation of the thickness, width, and area of three randomly selected specimens. 

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