Metrology (?) question.

[firewalker]

I was reading some question in order to prepare some students for a test. One question (translated) is:

Draw the static characteristic curve of a voltmeter, with 0 volts Zero Offset, with range 0:100% -> 0:300V, absolute error +3 volts at 10v and relative error 1% at 200V.

The answer (don't even know if it is correct. In fact I don't now if the question is correct) is the above drawing, with no explanation.



I search every book I own with metrology, electrical measurements errors and instruments. I could not find any relative reference to the above.

I can understand the point at 200,2. 1% relative error at 200V is 2volts. I can understand the graph starting a 0,0 as the 0 volts Zero Offset. Is the point at 300,5 a sum of relative error and absolute error?

Alexander.

[Simon]

The answer (don't even know if it is correct. In fact I don't now if the question is correct) is the above drawing, with no explanation.

Sounds like something out of the BTEC L3 course that I stuffed back at the providers due to it's inadequacy, where did it come from ? not that I'm an expert but makes no sense to me. if you have a "possible " error surely the graph should have more than one curve showing the expected ideal behavior and then ideally two dotted lines to illustrate the possible extremes the measurement could come out as given the tolerances stated. Giving a tolerance means that there will be no certain line but one you can hope to achieve and the possible extremes due to real world behavior. That is at least how thermistor manufacturers illustrate and graph the results from their sensors.

[firewalker]

It is from a set of ~300 of question that the candidate must be familiar with in order to succeed to the tests and obtain a technicians license.

Alexander.