Measurement Measurement means to compare somethingwith standard. E.g. measuring length of a wire, diameter of acylinder, depth of any object. The SI unit of length is meter (base unit). Its multiples and sub-multiples are given inthe table.
Meter and its sub-multiplesPrefix SymbolRelationship withMeter (base unit)meter m 1m = 1 mdeci dm 1dm = 10-1mcenti cm 1cm = 10-2mmilli mm 1mm = 10-3mmicro µm 1 µm = 10-6mnano nm 1nm = 10-9mpico pm 1pm = 10-12m
Meter and its multiplesPrefix SymbolRelationship withmeterdeca da 1 dam = 101mhecto h 1 hm = 102mkilo k 1 km = 103mmega M 1 Mm = 106mgiga G 1 Gm = 109m
Measuring Tools Vernier caliper Vernier caliper is a measuring device used to measureprecise increments between two points. Micrometer Micrometer is a measuring device used for preciselymeasuring thickness, inner and outer diameter, depth ofslots. SWG A gauge for measuring the diameter of wire, usuallyconsisting of a long graduated plate with similar slotsalong its edge.
Vernier caliper Function To measure smaller distances Can measure up to .001 inch or .01mm. Features Larger, lower jaws are designed to measure outer pointse.g. diameter of a rod. Top jaws are designed to measure inside points e.g. size ofa hole. A rod extends from the rear of the caliper and can be usedto measure the depth.
Structure of the Vernier caliper Main Scale Main scale is graduated in cm and mm. Vernier Scale It slides on the main scale. On Vernier scale 0.9cm is divided into 10 equal parts. Jaws Two inside jaws (Upper) Two outside jaws (Lower)
Least Count Least count (L.C) is the smallest reading we canmeasure with the instrument. L.C = one main scale division – onevernier scale divisionL.C = 1mm – 0.09mmL.C = 0.1mm = 0.01cm Least Count = Value of the smallest division on MS/Total number of division on VSL.C = 1mm / 10 = 0.1 cm / 10 = 0.01cm
How to use Vernier caliper?• Close the jaws• Calculate the least count• Place the object betweenthe two jaws• Record the position of zeroof Vernier scale on the Mainscale (3.2cm)• Notice the reading of VSwhich coincides with MSreading (3rddivision in thiscase)
Reading of the Instrument Reading of the instrument = MS div +(coinciding VS div x L.C) = 3.2 + (3 x 0.01) = 3.2 + 0.03 = 3.23 cm
To measure the depth A rod extends from the rear of the caliper andcan be used to measure the depth. Open the jaws of caliper and place the rodinside hole of the object, such as the rodreaches the inner most portion of the object. Read the Vernier caliper. (same procedure asdescribed in previous slides)
Micrometer Function Micrometer allows the measurement of the size of the bodyi.e. thickness, depth, inner/outer diameter. Features Two jaws (one fixed, one movable) Spring loaded twisting handle Easy to use and more précised Can measure up to .001cm
Structure of Micrometer Jaws 2 jaws (one fixed, one movable) Circular Scale Movable jaw is attached to a screw, scale on this screw iscalled Circular scale. Either 50 or 100 divisions Linear Scale Horizontal Scale
Structure of Micrometer Frame The C-shaped body that holds the anvil and sleeve in constant relation toeach other. Anvil The jaw which remains stationary. Spindle The jaw which moves towards the anvil. Lock Nut A lever, one can tighten to hold the spindle stationary. Sleeve The stationary round part with the linear scale on it. (Main Scale) Thimble Thimble rotates around the sleeve. Ratchet Stop Device on end of handle that limits applied pressure by slipping at acalibrated torque.
Pitch of Micrometer When the head of the micrometer rotatethrough one rotation, called pitch of themicrometer. The screw moves forward or backward 1mmon the linear scale. Pitch of Micrometer = distance on linearscale / one rotationPitch of Micrometer = 1/1 = 1mm
Least Count Least Count = Pitch of the Micrometer / Totalnumber of circular scale division Least Count = 1 / 100 = 0.01mm= 0.001cm
How to use Micrometer?• Thimble– The thimble rotates around acylinder which is marked inmillimeters.– The left-hand side of thethimble has markings allaround it.– The line labeled 0 is theprimary pointer.• Close the jaws• Calculate the least count• Place the object between thetwo jaws• Record the position of mainscale where the two measuringrods met.• Note the position of the circularscale which coincides withmain scale
Reading of the Instrument Reading of the instrument = MS div +(coinciding CS div x L.C) = 8+ (12 x 0.01) = 8 + 0.120mm = 8.120 mm = 8120 µm
Standard Wire Gauge (SWG) A gauge for measuring the diameter of wire, usuallyconsisting of a disk having variously sized slots in itsperiphery or a long graduated plate with similar slotsalong its edge. A standardized system of wire sizes. Wires are manufactured to standard sizes andlabeled with their SWG. As the SWG increases the diameter decreases.