Digital Measurement Equipment (Metrology)

2.60.
Digital indication is better by far when an exact quantitative value is desired.
The important elements of any electronic digital readout system are the scale unit or
transducer and the counter or digital readout unit.
The majority of linear digital readout systems comprise a glass scale and optical detector
head. These are however, liable to be affected under workshop conditions by contaminants such as
oil, swarf, and dirt. To overcome it some manufacturers have based their instruments on magnetic
principles. These instruments also provide binary coded digit (BCD) output which can be directly
fed to a computer or printer for further processing. In the case of instruments based on the principle
of magnetic recording, the linear scale comprises a magnetic strip which is unaffected by workshop
contaminants and can be of virtually any length.
Readout is provided by a range of digital display units and digital position readout units
which vary in complexity from a simple unit with one or two axis display and thumb wheel reset to
comprehensive three axis display multi-function capability. Functions such as datum point memory
for each axis, touch sensor (a touch to a workpiece starts counting or holds the display), manual
programming by key operation and automatic programming by play-back can be incorporated.
The advantages of such systems are ;
(i) Measuring element is free from errors caused by mechanical elements such as screws,
gears etc.
(ii) Learning time is short. Amateurs measure as quickly and as well as professionals.
Measurement takes half as long.
(iii) More accurate measurements, the spread of measurements and the mean error are
reduced to about 1/3.
(iv) Excessive reading errors are eliminated.
(v) The clear readability of digital readout is advantageous for persons with impaired vision.
(vi) The display can be zeroed wherever desired.
(vii) BCD output makes the instrument computer compatible.