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# Help with calculating percent error

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## Help with calculating percent error

If a current of 30 amps is measured with a 100 amp 3% ammeter, the maximum possible error in terms of actual error is:
Im having problems calculating these types of questions, could someone help?

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For percent error on that device:

100Amps X 3% = plus or minus 3 from 100 or a range of 97A to 103A when measuring 100A.

If the error is +/- 3 amps then your 30Amps may be 27A to 33A.

if the device is listed as a 3% tolerance over all measurement ranges then use 30A X 3% = plus or minus 0.9A or range of 29.1A to 30.9A

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Originally Posted by stuebes
For percent error on that device:

100Amps X 3% = plus or minus 3 from 100 or a range of 97A to 103A when measuring 100A.

If the error is +/- 3 amps then your 30Amps may be 27A to 33A.

if the device is listed as a 3% tolerance over all measurement ranges then use 30A X 3% = plus or minus 0.9A or range of 29.1A to 30.9A
The correct way is this. 30/3=10

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## Percentage error calculation

What am I missing if I keep coming up with 3.9%?

If 4000 was the specified value, and 3850 was the measured value, what is the percent error?

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## Percentage error

Please see below for percentage error calculation.

Step 1: Calculate the error (Subtract one value from the other)
Step 2: Divide the error by the specified value (we get a decimal number)
Step 3: Convert that to a percentage (by multiplying by 100 and adding a % sign)

% error =((Specified value-Measured value)/ Specified value )X 100 %

= ((4000-3850)/ 4000) X 100 %

= 0.0375 X 100 %
= 3.75%

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Originally Posted by Flashman
What am I missing if I keep coming up with 3.9%?

If 4000 was the specified value, and 3850 was the measured value, what is the percent error?
I always do
[expected (specified) - Calculated (Measured)] / expected (specified)

this will give you a decimal, which can be converted into a percentage by multiplying by 100

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Originally Posted by Mmfz85
The correct way is this. 30/3=10
The correct way is;
2% of 100 is 2.
2 is the maximum error.
2/30 is 0.0667 which is 6.6%

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