Length is defined as the distance between any two points. Its International System of Units measurement is the meter (m), though other prefixes are added when the length is great or small. There are several precision instruments that measure length or distance with great accuracy. A vernier calipers and micrometer screw gauge are examples of such instruments. The vernier calipers measures both internal and external lengths to a high accuracy of degree. In fact, the accuracy of the vernier calipers is 1/20th a millimeter. There are two types of calipers; manual and digital. When using the manual calipers, you have to read the scales to obtain a reading. The digital one, on the other hand, has a LCD display that shows the observed reading. The micrometer screw gauge offers even more accuracy than the vernier calipers. So accurate is this instrument, it can measure the diameter of a wire. The accuracy of a micrometer screw gauge is 1/100 of a millimeter. Both of these instruments are mainly employed in mechanical and civil engineering.
Electrical engineers encounter certain parameters in their day-to-day work. Measurements such as voltage and current are but a few of these parameters. Voltage in an electric circuit is measured by a voltmeter. The instrument displays the reading in units called volts (V). Current is measured by using an ammeter connected in series with the circuit. The readings of the ammeter are in amperes, denoted by the letter A. However, an instrument that can measure both parameters exists. This instrument is known as a multimeter and can be set to function as both an ammeter and a voltmeter.
Hardness of materials is determined using a Vickers hardness tester. Testing of hardness of materials is essential, especially to civil engineers, as it helps establish the type of material to be used in a particular construction. The Vickers hardness tester tests the ability of a given material to resist plastic (permanent) deformation. The machine is widely employed to test the tensile strength of metals. The Vickers hardness machine gives the units for hardness in units of Vickers Pyramid Number (HV). A Brinell machine is also used to find the hardness of metals. The units when using this machine are the Brinell hardness number (BHN)
Electric resistance is defined as the measure of opposition offered by a conductor to the flow of current. Electric resistance is measured by an ohmmeter and the units for this parameter is ohms. The ohmmeter first measures the voltage drop across a circuit and then converts the corresponding reading into resistivity. Advancements have made it possible to measure very small resistivity of materials. In this case, a micro ohmmeter is employed.