2.2.7 Threshold
If the input to an instrument is gradually increased from zero, the input
will have to reach a certain minimum level before the change in the instrument
output reading is of a large enough magnitude to be detectable. This minimum
level of input is known as the threshold of the instrument. Manufacturers vary
in the way that they specify threshold for instruments. Some quote absolute
values, whereas others quote threshold as a percentage of full-scale readings.
As an illustration, a car speedometer typically has a threshold of about 15
km/h. This means that, if the vehicle starts from rest and acceler[1]ates, no output
reading is observed on the speedometer until the speed reaches 15 km/h.
2.2.8 Resolution
When an instrument is showing a particular output reading, there is a
lower limit on the magnitude of the change in the input measured quantity that
produces an observable change in the instrument output. Like threshold,
resolution is sometimes specified as an absolute value and sometimes as a
percentage of f.s. deflection. One of the major factors influencing the
resolution of an instrument is how finely its output scale is divided into
subdivisions. Using a car speedometer as an example again, this has
subdivisions of typically 20 km/h. This means that when the needle is between
the scale markings, we cannot estimate speed more accurately than to the
nearest 5 km/h. This figure of 5 km/h thus represents the resolution of the
instrument
No comments:
Post a Comment
Tell your requirements and How this blog helped you.