Selection of instruments

It is a challenging task for instrument engineers to select instruments considering all parameters. The engineer has to consider factors such as accuracy, resolution, sensitivity and dynamic error.

Following points must be considered while choosing an instrument for certain application:

1. External environmental conditions such as temperature, humidity are the one main factor which limits the performance of the instrument. The protection is one of the performance-limiting factors of the instruments that means the technology can perform the required task but the usage in such an environment may be dangerous. It is the main factor that increases the cost of the instruments because the instrument has to have such quality’s to perform the required task.
2. Consideration of durability, maintainability, and consistency of performance is also very important during selecting the appropriate instrument.
3.  Identify all operating cases, such as normal operation at minimum, normal and maximum flow, alternative operating modes, start-up, commissioning and emergency operation.
4. Manufacturing costs also play a key role in selection. Cost is proportional to the desired characteristics. For example, to make an instrument that is highly accurate and precise the cost increases.

Therefore, instrument choice is a compromise between performance characteristics, ruggedness and durability, maintenance requirements, and purchase cost.

To carry out such an evaluation properly, the instrument engineer must have a wide knowledge of the range of instruments available for measuring particular physical quantities, and he/she must also have a deep understanding of how instrument characteristics are affected by particular measurement situations and operating conditions.