Errors in Measuring Instruments

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

1) Assembly Errors

The assembly errors are the errors in the measuring instrument due to improper m________ring of the instruments. Various co_________nts of the instrument are made separately and then they are as_________ed together. There may be errors in the ind________l components or in the assembly of the components. If there are assembly errors in the instruments, the instrument will just not give the correct re_______g 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 s____e: This is the incorrect fitting of the measuring sc____. For instance the zero of pointer may not coincide with actual zero on the scale. Sometimes the scale gets cracked, thus showing the faulty r_______gs.

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

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

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

Exercise 2. Translate the following text in written.

2) Environmental Errors

The measuring instruments are assembled and calibrated in certain environmental conditions and are designed to be used in within certain restricted conditions, but when they are used in different conditions, there are errors in measurement, which are considered to be the environmental errors. Most of the instruments are designed to be used within certain limits of temperature, pressure, humidity, altitude, etc., and when the limits are extended there are errors in the measuring instruments.

It is quite easier to find the assembly errors in instruments, but the errors due to change in environmental conditions are highly unpredictable. These errors can be sometimes positive, sometimes negative and sometimes combination of the both.

Here are some precautions to be taken to reduce the environmental errors in the instruments:

a) Use in the instruments within the specified limits of temperature, pressure and humidity for which the instrument has been designed. These limits are mentioned in the instruments instructions manual.

b) If you have to use the instrument beyond the specified limits of environmental conditions, then apply suitable corrections to the recorded measurement.

c) One can also calibrate the instrument newly in the new conditions.

d) There are some devices that enable applying the compensation automatically.