# Calculate the percent of span error

An important part of performing instrument calibration is determining the extent of an instrument’s error. Error is usually measured in percent of span.

Calculate the percent of span error for each of the following examples, and be sure to note the sign of the error (positive or negative):

### Pressure gauge

• LRV = 0 PSI
• URV = 100 PSI
• Test pressure = 65 PSI
• Instrument indication = 67 PSI
• Error = % of span

### Weigh scale

• LRV = 0 pounds
• URV = 40,000 pounds
• Test weight = 10,000 pounds
• Instrument indication = 9,995 pounds
• Error = % of span

### Thermometer

• LRV = -40oF
• URV = 250oF
• Test temperature = 70oF
• Instrument indication = 68oF
• Error = % of span

### pH analyzer

• LRV = 4 pH
• URV = 10 pH
• Test buffer solution = 7.04 pH
• Instrument indication = 7.13 pH
• Error = % of span

Also, show the math you used to calculate each of the error percentages.

Pressure gauge

• LRV = 0 PSI • URV = 100 PSI • Test pressure = 65 PSI • Instrument indication = 67 PSI
• Error = +2 % of span

Weigh scale

• LRV = 0 pounds • URV = 40,000 pounds • Test weight = 10,000 pounds • Instrument indication = 9,995 pounds
• Error = -0.0125 % of span

Thermometer

• LRV = -40oF • URV = 250oF • Test temperature = 70oF • Instrument indication = 68oF
• Error = -0.69 % of span

pH analyzer

• LRV = 4 pH • URV = 10 pH • Test buﬀer solution = 7.04 pH • Instrument indication = 7.13 pH
• Error = +1.5 % of span

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