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

## Instrument Percent of Span Error

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):

**Question 1:**

#### Calculate the percent of span error for Pressure gauge as per the below details.

LRV = 0 PSI

URV = 100 PSI

Test pressure = 65 PSI

Instrument indication = 67 PSI

**Question 2:**

#### Calculate the percent of span error for weigh scale as per the below details.

LRV = 0 pounds

URV = 40,000 pounds

Test weight = 10,000 pounds

Instrument indication = 9,995 pounds

**Question 3:**

#### Calculate the percent of span error for thermometer as per the below details.

LRV = -40 ^{o} F

URV = 250 ^{o} F

Test temperature = 70 ^{o} F

Instrument indication = 68 ^{o} F

**Question 4:**

#### Calculate the percent of span error for Ph analyzer as per the below details.

LRV = 4 pH

URV = 10 pH

Test buﬀer solution = 7.04 pH

Instrument indication = 7.13 pH

## Percent of Span Error Formula

Answer 1

Error = +2 % of span

Answer 2

Error = -0.0125 % of span

Answer 3

Error = -0.69 % of span

Answer 4

Error = +1.5 % of span

Credits: Tony R. Kuphaldt

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