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.