Suppose that a standard bourdon tube pressure gauge has a scale of 0 to 1000 psig. If the accuracy of the gauge is plus or minus .5% of the span, what would the range of measured pressure be if the gauge indicates 690 psig?
• Span vs. indicated reading on a pressure gauge • How to compute percentage of full-scale span (0–1000 psig) • Using a tolerance band around the indicated value
• First, decide what number you apply the 0.5% to: is it the full-scale span (0–1000 psig) or the current reading (690 psig)? • After you find the pressure error in psi, how do you use it to build a high and low possible reading around 690 psig? • Compare the width of your tolerance band with the answer choices: which one matches your calculated plus/minus range?
• Confirm that span means the full measuring range: 0 to 1000 psig, not the current reading. • Compute 0.5% of 1000 psig carefully and convert that percent to psi. • Check that your final range is symmetric around 690 psig (same psi added and subtracted).
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