ELECTRONIC
MEASUREMENT AND
TESTING
Unit 53
This unit will give learners the
knowledge and skills needed to
carry out a range of
measurements on electronic
circuits and equipment.
Fahim Mohammed (Student Y13)
, Unit 53 Measurement Instruments & Test Equipment Assignment 1
For this new unit, I will begin by describing the function, features & characteristics of
a measurement instrument.
Firstly, there are 2 types of characteristics of instruments, which are:
- Static
- Dynamic
Static characteristics of an instrument measure quantities that don’t differ with time;
& need to be reflected for those instruments that measure regular process
conditions.
An instrument system is mainly created from a sequential connection of distinct
building blocks. The physical assembly can be broken down into an illustrative
diagram of connected blocks. The sensor is triggered by an input physical parameter
& gives an output signal to the next block that processes the signal into a more
suitable state. A vital depiction of a block is to create a bond between the input &
output of the block, where all the signals have a time characteristic. The
performance of the static system alone & the combined static & dynamic system can
be located through the use of a suitable mathematical model of each block.
There are a numerous amount of characteristics for static characteristics, & I will
mention a few of them below:
- Accuracy: This is essentially the degree of closeness with which an
instrument reading comes to the true value of the quantity that’s being
measured. Also, the more accurate the measurement is
- Drift: Categorised into 3 categories: Zero Drift, Span Drift (Sensitivity Drift) &
Zonal Drift. As the gradual shift in the indication over a period of time where
in the input variable doesn’t change. Drift may occur due to the fact that
environment factors, like stray electric fields, stray magnetic fields, changes
in temperature etc.
- Static Error: This is the aberration from the true value of the measured
variable. Likewise, it consists of comparing an unidentified quantity with an
established standard quantity. Now, the degree to which an instrument
comes to its excepted value is shown in terms of error of measurement.
- Dead Zone: Displays the largest alterations of input quantity for which there
is no output; e.g. the input that is applied to an instrument may not be
enough to overawed friction, but will react when it overcomes the friction
forces.
- Threshold: Smallest measurable input where no output change can be
recognised, & while postulating threshold, manufactures give the first
measurable output change.
- Linearity: This is the ability of an instrument to replicate its own input
linearly. Linearity is essentially a measure of the maximum deviation of the
adjustment points from the best straight line.
- Bais: The constant error that occurs over the full range of measurement of an
instrument. Bais can be totally eradicated by calibration.
- Hysteresis: Displays different output properties whilst packing & unpacking.
Hysteresis takes place because all the energy that is put into the stressed
P1 Fahim Mohammed