Continue to Site

# I need the exact definition of Accuracy.

Status
Not open for further replies.

#### iVenky

Let's say that I have a battery whose voltage is 5 V. I say that it has 2% accuracy. What is its deviation from the ideal value then? I just don't know the exact definition of accuracy ?

Suppose the battery is to power a device which needs a 5V supply.

You are saying the battery is guaranteed to produce between 4.9 and 5.1 V. Meaning within an accuracy of 2%.

This requires that you measured it with a voltmeter which is accurate to within 2%.

It looks as if there is 2% error. I mean 100% accuracy means 100% error?

Accuracy v precision, In the above example the next time you measure the 5V, you might measure 4.9, and the next time 5.1. If its a precision device, it may measure it at 4.8, but it will ALWAYS measure it at 4.8. So accuracy equates to limited uncertainty, precision equates to repeatability. Of course its best to have both
Frank

It looks as if there is 2% error. I mean 100% accuracy means 100% error?

I guess I never thought about that before. This is one of those figures of speech that becomes hard to pin down.

When we say '100 percent' it gives the impression of perfect and complete.

On that basis, to be consistent we would have to say your battery is '98% and 102% accurate'.

But nobody would understand what you're saying. It's too awkward.

So we say its accuracy is 2% (or within 2%). And people understand its error is plus or minus that much. It is between 98% and 102% of the correct figure.

According to wikipedia

"An accuracy of 100% means that the measured values are exactly the same as the given values."

which is not the case in the above problem.

- - - Updated - - -

I guess I never thought about that before. This is one of those figures of speech that becomes hard to pin down.

When we say '100 percent' it gives the impression of perfect and complete.

On that basis, to be consistent we would have to say your battery is '98% and 102% accurate'.

But nobody would understand what you're saying. It's too awkward.

So we say its accuracy is 2% (or within 2%). And people understand its error is plus or minus that much. It is between 98% and 102% of the correct figure.

Ya I get it. I was confused mainly because of that 2% accuracy. Who will build a battery which is just 2% accurate? Now I get that meaning.

Status
Not open for further replies.