Types of Errors in a Measurement System

1. Instrument Error:

1. Improper selection and poor maintenance of instruments.
2. Loss of motion due to necessary clearance in gear teeth and bearing.
3. Excessive friction at the mating parts, etc.

2. Environmental Error:

1. Using an instrument in conditions different from which it was designed, assembled, and calibrated.
2. Factors such as temperature, pressure, humidity, and altitude can introduce errors.
3. Methods to reduce environmental errors include using the instrument under the correct conditions, applying suitable corrections, or performing a new calibration.

3. Translation and Signal Transmission Errors:

1. Inaccurate sensing or translation of the measured effect.
2. Non-capability of the instrument to follow rapid changes in the measured quantity due to inertia and hysteresis effects.
3. Unwanted disturbances like noise, line pickup, hum, ripple, etc.
4. Remedied through calibration and monitoring the signal at various points along its transmission path.

4. Observational Error:

1. Parallax.
2. Inaccurate estimation of average readings.
3. Incorrect conversion of units between consecutive readings.
4. Personal bias, i.e., a tendency to read high or low.
5. Wrong scale reading and incorrect data recording.

5. Operational Error:

1. Errors caused by poor operational techniques.
2. Examples include incorrect placement of flow meters or thermometers, insufficient immersion of thermometers, and exposure of pressure gauges to incorrect pressures.