Definition of Full-scale error

Question

I was looking for the concept of "Full-scale error" (related with laboratory measurement terminology) on the web without success. I would appreciate your help.

I just Googled "full scale error", got some 85 million hits, and just a cursory glance at the first page showed some good stuff. — EM Fields, Oct 10 '15 at 12:44

score 2 · Accepted Answer · answered Aug 02 '14 at 22:21

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An error expressed as a percentage of full scale means that any measurement made will fall between the limits given by that quantity.

For example, an analog voltmeter with a range of zero to 100 volts specified as having an accuracy of +/-1% of full scale can be off by plus or minus 1 volt when there's between zero and 100 volts across the meter.

So, with the meter reading 1 volt, the actual input could be anything between zero and two volts, and with the meter reading 100 volts the actual input could be anywhere between 99 and 101 volts.

answered Aug 02 '14 at 22:21

EM Fields

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why is it better to state +/-1%FS , than simply say +/-1Volt ? – nass Oct 09 '15 at 14:53
I don't believe it even came up, let alone being touted as "better". – EM Fields Oct 09 '15 at 16:22
i am looking for the reason why companies may choose to state the error in one way or the other... – nass Oct 10 '15 at 11:39
Probably because that's the way it's done, and everyone - Well, almost everyone - understands what it means. – EM Fields Oct 10 '15 at 12:36
there is definitely a reason other than "it has existed like so". – nass Oct 10 '15 at 15:40
OK, good luck with your "research". – EM Fields Oct 10 '15 at 22:05

Spehro Pefhany · Answer 2 · 2022-06-05T21:54:05.143

The definition varies a bit, but often it must be added to a 'zero' error, and unless otherwise specified, applies only under reference conditions- warmed up for 1 hour, ambient temperature 20°C +/-1°C or whatever. Temperature changes to scale and zero, and aging often must be added on top of that. In the case of thermocouple instruments, the cold-junction compensation is added on top (and may be specified as a ratio such as 20:1, meaning a 20°C change in ambient temperature could cause an additional 1°C error).

An error specification of 1% F.S. means that if the scale is 4mA to 20mA, that error will not exceed +/-160uA (1% of the full scale deflection, which is 20mA-4mA = 16mA). If they're complete d*cks it could mean +/-2uA error, as I said, definitions vary.

So if the measurement is at mid-scale (12mA) then that error could be +/-2% of reading.

I think you mean the 'error will not exceed +/- 160uA '- right? — efox29, Jun 05 '22 at 20:44

score 1 · Answer 3 · answered Aug 02 '14 at 21:37

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As an example, an error of 10 mV in a full-scale deflection of 2V would be a "full-scale error" of 0.5%. In other words you compare the error with the limits of measurement of the device and express that as a percentage.

answered Aug 02 '14 at 21:37

Andy aka

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Definition of Full-scale error

3 Answers3