Fluke 5502A - Calculate Power Uncertainty; Examples of Specified Power Uncertainties at Various Output Settings

5502A
Operators Manual
1-22
Examples of Specified Power Uncertainties at Various Output Settings:
Selected Output Settings
Absolute Uncertainty as
specified for tcal ±5 °C, ±(% of
output setting)
Power
Absolute
Uncerainty
±(% of
Watts)
[1]
V
oltage
Setting
(Volts)
Current
Setting
(Amps)
Frequency
Hz
Phase
Setting
(units of PF)
Phase
Setting
(Degrees)
Selected
Power
(Watts)
U
Voltage
U
Current
U
Phase
U
Power
+10.000 +0.500.000 DC
5 0.00550 % 0.04680 %
0.047 %
15.000 +2.0000 DC 30 0.00533 % 0.03220 % 0.033 %
100.000 +20.000 DC 2000 0.00600 % 0.10375 % 0.104 %
1000.00 20.000 DC 20000 0.00565 % 0.10375 % 0.104 %
120.000 1.00000 60 1 0.0 120 0.05250 % 0.06000 % 0.000 % 0.080 %
120.000 1.00000 60 0.766 40.0 91.92 0.05250 % 0.06000 % 0.220 % 0.234 %
240.000 1.00000 50 1 0.0 240 0.05125 % 0.06000 % 0.000 % 0.079 %
240.000 1.00000 50 0.766 40.0 183.84 0.05125 % 0.06000 % 0.220 % 0.234 %
1000.00 20 55 1 0.0 20000 0.05200 % 0.14500 % 0.000 % 0.154 %
1000.00 20 55 0.766 40.0 15320 0.05200 % 0.14500 % 0.220 % 0.269 %
1000.00 20 55 -0.906 -25.0 18120 0.05200 % 0.14500 % 0.122 % 0.196 %
100 0.30 30000 1 0.0 30.0 0.12900 % 0.4667 % 3.407 % 3.442 %
100 0.30 30000 0.766 40.0 22.98 0.12900 % 0.4667 % 25.128 % 25.133 %
[1] Add 0.02 % unless a settling time of 30 seconds is allowed for output currents >10 A or for currents on the highest two current
ranges within 30 seconds of an output current >10 A.
Calculate Power Uncertainty
Overall uncertainty for power output in watts (or VARs) is based on the root sum square (RSS) of the individual
uncertainties in percent for the selected voltage, current, and phase parameters:
Watts uncertainty
Phase
2
Current
2
VoltagePower UUUU
2
++=
VARs uncertainty
Phase
2
Current
2
VoltageVARs UUUU
2
++=
Because there are an infinite number of combinations, you must calculate the actual ac power uncertainty for your
selected parameters. The method of calculation is best shown in the subsequent examples (with 1-year specifications):
Example 1 Output: 100 V, 1 A, 60 Hz, Power Factor = 1.0 (Φ=0).
Voltage Uncertainty Uncertainty for 100 V at 60 Hz is 0.050 % + 3 mV, totaling: 100 V x .0.0005 = 50 mV added to
3 mV = 53 mV. Expressed in percent: 53 mV/100 V x 100 = 0.053 % (see “AC Voltage (Sine Wave) Specifications”).
Current Uncertainty Uncertainty for 1 A at 60 Hz is 0.05 % +100 μA, totaling: 1 A x 0.0005 = 500 μA added to
100 μA = 0.6 mA. Expressed in percent: 0. 6 mA/1 A x 100 = 0.06 % (see “AC Current (Sine Waves) Specifications”).
Phase Uncertainty (Watts) Adder for PF = 1 (Φ=0) at 60 Hz is 0 % (see “Phase Specifications”).
Total Power Uncertainty =
%080.0006.0053.0U
22
power
=++=
2
Example 2 Output: 100 V, 1 A, 400 Hz, Power Factor = 0.5 (Φ=60)
Voltage Uncertainty Uncertainty for 100 V at 400 Hz is 0.050% + 3 mV, totaling: 100 V x .0.0005 = 50 mV added to
3 mV = 53 mV. Expressed in percent: 53 mV/100 V x 100 = 0.053 % (see “AC Voltage (Sine Wave) Specifications”).
Current Uncertainty Uncertainty for 1 A at 400 Hz is 0.05 % +100 μA, totaling: 1 A x 0.0005 = 500 μA added to
100 μA = 0.6 mA. Expressed in percent: 0. 6 mA/1 A x 100 = 0.06 % (see “AC Current (Sine Waves) Specifications”).
Phase Uncertainty (Watts) Adder for PF = 0.5 (Φ=60) at 400 Hz is 2.73 % (see “Phase Specifications”).
Total Power Uncertainty =
%73.273.206.0021.0U
22
power
=++=
2
VARs When the Power Factor approaches 0.0, the Watts output uncertainty becomes unrealistic because the dominant
characteristic is the VARs (volts-amps-reactive) output. In these cases, calculate the Total VARs Output Uncertainty, as
shown in example 3:
Example 3 Output: 100 V, 1 A, 60 Hz, Power Factor = 0.174 (Φ=80)
Voltage Uncertainty Uncertainty for 100 V at 60 Hz is 0.050% + 3 mV, totaling: 100 V x .0.0005 = 50 mV added to
3 mV = 53 mV. Expressed in percent: 53 mV/100 V x 100 = 0.053 % (see “AC Voltage (Sine Wave) Specifications”).
Current Uncertainty Uncertainty for 1 A at 60 Hz is 0.05 % +100 μA, totaling: 1 A x 0.0005 = 500 μA added to
100 μA = 0.6 mA. Expressed in percent: 0. 6 mA/1 A x 100 = 0.06 % (see “AC Current (Sine Waves) Specifications”).