How To Display The Uut Error - Fluke 5522A Operator's Manual

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Front Panel Operation
Editing and Error Output Settings

How to Display the UUT Error

When you edit the output value, the Control Display shows the difference between the
reference value (the value you originally entered) and the edit value (the value shown in
the Output Display), displaying error difference in parts per million (ppm) or percent (%).
For example, if ERR UNI is set to > 100 ppm, the error will be displayed in ppm up to 99
and then the error will change to 0.0100 % at 100 ppm. This allows you to edit the output
such that the UUT displays the expected value and thus give an indication of the UUT
accuracy.
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For example, an edited difference of .00030 volts for an output of 10.00000 V represents
0.00030/10.00000=0.000030, or 30 parts per million. The sign is negative (-30.0 ppm)
because the output necessary to display 10.00000 at the UUT shows the UUT is reading
below the output value. When the reference is negative, the error sign is relative to the
magnitude. For example, if the reference is -10.00000 V and the output display
is -10.00030, the error is -30 ppm.
The Calibrator has two methods of displaying the UUT error. The first method, called the
"nominal" method is used in the Fluke 5700A, 5720A, 5500A, and 5520A calibrators.
The second method is called "true value". Both methods are used in this Calibrator.
The nominal method of error calculation uses the formula:
reference value – edit value
reference value
The nominal method is useful for checking the error of the Calibrator itself, when you are
verifying its performance against a more accurate measuring device.
The true value method of error calculation uses the formula:
Reference value – edit value
edit value
With either the nominal or true value method, small changes in output value result in a
calculated error that is the same. In the example above, the Control display will show the
error as -30.0 ppm.
The true value method is useful for large changes in output value. For example, if you
apply 10.0000 V to an analog meter, and then adjust the calibrator output to 11.0000 V
such that the analog meter now reads exactly 10 V, the true value method will display
nominal= +10.0000 V
rel err= -9.0909 %
The -9.0909 % represents the relative error of the analog meter when compared to the
true value (11.0000 V in this case).
To select the UUT error calculation method:
1. Press the key.
2. Press the softkey INSTMT SETUP.
3. Press the softkey OTHER SETUP.
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