total quantitative systematic error, and R

is the final result in the

measurement.

9.

COMPUTATION OF ERRORS.

a. You will use one of the two basic procedures in calibration.

In

either case, an allowable error tolerance will be given, expressed as a or

e.

b. The normal procedure is to set the test instrument (TI) to full

scale or at a major scale division, which will be R. The standard is then

used to check the TI.

The difference between the reading on the standard

and the reading on the TI is a. Percent error may be computed then, using

the formula a/rx100%.

Example: A 10 volt, full-scale voltmeter is

calibrated at the full-scale point.

The meter has a manufacturer's

tolerance of 3% of full scale (FS). A variable voltage source is connected

to the meter (TI) and adjusted to cause the TI to read exactly 10 volts. A

standard meter is also connected to the voltage source and reads the true

value, 9.7 volts (figure 6).

Figure 6.

Full Scale Calibration

Example: A 10 volt, full-scale voltmeter is read at the half-scale mark of

five volts (figure 7).

The meter is 3% at FS.

The percentage of error

changes at the 5 volt reading.

r=5 volts, a=0.3 volt, and e=6%.

The

quantitative error remains 0.3 volt.

Figure 7.

Half-scale Reading

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