In the past and until recently, most of
electrical loads were linear, that is the impedance of the load remains
constant regardless of the applied voltage, so electricity measurement interested
people used conventional meters that measure the average value of the current
and voltage. This method was true until the appearance of non linear loads like
"UPS", computers, motor variable speed drives and generally the electronic
loads, all these types of loads are non linear load which distort the current
and voltage wave shape and resulted in nonsinusoidal wave form.
Measuring the non sinusoidal current
and voltage wave shape require a true RMS meter as only this meters gives
accurate readings for the nonsinusoidal waveform.
What is the
meaning of the term "RMS"?
It means root mean square value and
only used for AC current and it refers to the amount of work done by the
equivalent value of direct current (DC). Or, RMS value of A.C supply is the
steady DC which will convert electrical energy to thermal energy at the same
rate in a certain resistance.
RMS is is a must to describe the value
of alternating current and voltage especially for non linear distorted wave
form.
How can RMS
meters measure current and voltage?
These meters incorporate electronic
measuring circuit that sample the input at a high rate of speed and then digitize
and square each sample adding it to previous sample squared and finally it takes
the square root of the total.
Electricity
measurement becomes a must, as we cannot indicate the quality of the power
supply without it and there is no doubt that good power quality of electricity
supply will save much much money.
Post a Comment