Errors in Measuring Instruments

When we measure any physical quantity like temperature, pressure, voltage, current etc we take it for granted that the instruments are accurate. Very few people can imagine that there can be errors in the instrument they are using, but there are possibilities of errors in the measuring instruments especially the analogue instruments that indicate the magnitude or value by the movement of the pointer. There are three types of errors in the measuring instruments: assembly errors, environmental errors, and random errors. All these have been discussed below.

The assembly errors are the errors in the measuring instrument due to improper manufacturing of the instruments. Various components of the instrument are made separately and then they are assembled together. There may be errors in the individual components or in the assembly of the components. If there are assembly errors in the instruments, the instrument will just not give the correct reading and the user can hardly do anything about it, but return it and get the new one. Here are some of the possible assembly errors:

a) Displaced scale: This is the incorrect fitting of the measuring scale. For instance the zero of pointer may not coincide with actual zero on the scale. Sometimes the scale gets cracked, thus showing the faulty readings.

b) Non-uniform scale: Sometimes the scale of the measuring instrument is not divided uniformly. In some part of the scale the markings may be too close and in other parts too far.

c) The pointer is bent: This happens in many cases. The pointer may get bent in either horizontal direction or the vertical direction, in either case, is shows erroneous reading.

d) Manufacturing errors in the components: The instruments are made up of a number of small components, which may be manufactured in different places. Sometimes there are manufacturing errors in some of these components like gear, lever, links, hinges etc.