Factors for selecting instruments for measurements
Describe the factors listed in Q3(a) above. [6 marks]These are various factors to be considered when selecting instrument for measurement. They are Range, Accuracy, Response, Input, Output, Stability, Operation, Reliability and Sensitivity.
(1) RANGE: This can be defined as the difference between the nominal value of the measures quantities corresponding to the scale in which the instrument can measure.
(2) ACCURACY: This can be defined as the extent to which the indicators of an instrument approach the true values of the quantities measured.
Factors that can affect the accuracy of the indicator of an instrument are:
- Temperature: Some instruments like analogue are affected by atmospheric condition.
- Humidity: Moisture can affect instrument.
- Voltage: There is a limit to which a very low or high voltage can give accuracy since the voltage of the instrument used is not corresponding to what is been measured.
- Waveform: It’s important to understand the types of waveforms associated with vibration analysis which may cause variation of units.
- Proximity [to other instruments]: its closeness or how other instrument can reach also matters.
- Overload: If the load measured is more than the instrument scale it may bring about inaccuracy or the instrument damage. Take for instance, if an ammeter used in the laboratory which does not have a maximum range of scale is used to measure HIGH TRANSMISSION line electricity, what do you think will happen, of course there will be damage of the instrument..
- Vibration: Vibration of an instrument to be measured may cause variation of units or scale.
(3) RESPONSE: This can be defined as the performance of the instrument or measuring system to the full effect of an input signal. If it do not show quickly, it is due to a lag or delay. This delay is called measurements lag.
Input: This can be defined as the energy that is measured by an instrument that have the same range with it. OR This can be defined as the useful energy an instrument of measuring device can take once at a particular time.
(4) STABILITY: This can be defined as the ability of an instrument to return to it’s initial [zero reading] after the measured quantities has returned to zero. ( if an instrument after measuring an input can return to its initial scale, it is said to be stable).
(5) OUTPUT: This is the opposite of input. It simply means the useful energy an instrument or measuring device can deliver at a particular time.
(6) OPERATION: This is the ability of an instrument to work or perform its function within a stated format, procedure, limit and standard.
The standard are classified as;
(7) RELIABILITY: This is the ability of an instrument to perform a required operation/function under a stated condition for a stated period of time.
(8) SENSITIVITY: This is the response of an instrument to be able to observe every change that happens in its surrounding or environment. OR is the relationship between a change in the output reading for a given change of the input.
LIST FOUR  BASIC ACTIONS DEVELOPED IN A SIMPLE METER OPERATION OF A RELATIVELY COMPLICATED INSTRUMENTATION PROCEDURE
Acquisition – .it is the process of getting materials needed
Preparation – It is used to retrieve, arranged or setup.
Processing- it is the process of working on the materials
Interpretation- it is the process of interpreting the information