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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
Testing Guidelines (Protocol) for E
NERGY
S
TAR
®
Qualified Set-Top Boxes
July 2000
This protocol should be followed to ensure consistency in measuring the power requirements for E
NERGY
S
TAR
®
qualified set-top boxes. Outlined in Section I are the ambient test conditions that should be
respected when performing power measurements. These conditions ensure that outside factors do not
affect the test results and that the test results can be reproduced. Sections II and III describe the
specifications for testing equipment and the test method, respectively. Section IV reviews responsibilities,
while Section V covers continuing verification. Questions and Answers complete this document.
I.
T
EST
C
ONDITIONS
General Criteria:
Total Harmonic Distortion (Voltage):
< 3% THD
Ambient Temperature:
22ºC ± 4 ºC
Terminations: External speaker terminals terminated per 3.6.2.2 (IEC 107-1)
Market-Specific Criteria:
Market:
United States
Europe and Australia
Japan
Voltage:
115 V RMS
±3 V RMS
230 V RMS
± 10 V RMS
100 V RMS ± 5 V RMS &
200 V RMS ± 10 V RMS
Frequency:
60 Hz ± 3 Hz
50 Hz ± 3 Hz
50 Hz ± 3 Hz & 60 Hz ± 3 Hz
Note: Testing needs to be done only at a voltage and frequency in the above range. It is not necessary to
test all combinations of high voltage/low frequency, high voltage/high frequency, etc.

E
NERGY
S
TAR
is a registered U.S. mark. Testing Guidelines (Protocol) for E
NERGY
S
TAR
®
Qualified Set-Top Boxes - July 2000
2
II.
T
EST
E
QUIPMENT
Manufacturers should measure and report the true standby/low-power mode
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requirements of the product.
Doing so necessitates the use of a true power watt meter. Because there are many watt meters from which
to choose, manufacturers need to exercise care in selecting an appropriate model. The following items
should be considered when procuring equipment and performing the test:
1. AC Power Source (with sufficient output current for the test unit such that it meets the requirement
for AC line voltage, frequency stability, and THD).
2. True Power Meter (with sufficient accuracy, resolution, crest factor rating, and bandwidth).
3. Oscilloscope with Current Probe (to monitor AC line current waveform, amplitude, and frequency.
Optional but recommended).
4. True RMS Volt Meter (to verify voltage at the input of test unit. Optional if AC source output is
sufficiently accurate).
5. Frequency Counter (to verify frequency at the input of test unit. Optional if AC source output is
sufficiently accurate).
Crest Factor
Electronics equipment may draw current that is not sinusoidal.
2
While virtually any watt meter can
measure a standard current waveform, it is more difficult to select a watt meter when irregular current
waveforms are involved.
It is critical that the watt meter selected be capable of reading the current drawn by the product without
causing internal peak distortion (i.e., clipping off the top of the current wave). This requires a review of
the meters crest factor rating and the current ranges available on the meter. Better quality meters will
have higher crest factor specifications and more choices of current ranges.
To determine the crest factor rating requirement of the meter and the proper current range settings, the
peak current (amps) draw of the product under test in standby/low-power mode must first be measured.
This can be accomplished using an oscilloscope with a current probe.

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True power is defined as (volts)x(amps)x(power factor) and is typically reported as watts. Apparent power is
defined as (volts)x(amps) and is usually expressed in terms of VA or volt-amps. The power factor for equipment
with switching power supplies is always less than 1.0; therefore, true power is always less than apparent power.
2

The crest factor of a current waveform is defined as the ratio of the peak current (amps) to the RMS current
(amps). The crest factor for a sinusoidal 60 Hz current waveform is always 1.4. The crest factor for a current
waveform associated with a product containing a switching power supply will always be greater than 1.4 (though
typically no higher than 8). Testing Guidelines (Protocol) for E
NERGY
S
TAR
®
Qualified Set-Top Boxes - July 2000
3
A current range on the meter must be selected that is sufficient to register the peak current. Specifically,
the full-scale value of the selected current range multiplied by the crest factor of the meter (for current)
must be at least 15% greater than the peak current reading from the oscilloscope to compensate for any
measurement error. (Note: It is difficult to measure within 5% using an analog oscilloscope.) For
example, if a watt meter has a crest factor of 4 and the current range is set on 3 amps, the meter can register
current spikes of up to 12 amps. If measured peak current is only 6 amps, the meter would be satisfactory.
If, however, the current range is set too high, the meter may lose accuracy in measuring non-peak current.
Therefore, some delicate balancing is necessary. When choosing a meter, make sure that the crest factor is
given for the current level that you desire.
Figure 1
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
-80
20
120
220
320
420
520
620
720
Time
Current (Amps)
Current of Unit
Under Test
Sinewave Current
Frequency Response
Another issue to consider when selecting a watt meter is the frequency response rating of the meter.
Electronics equipment may cause harmonic waveforms that can lead to inaccuracies in the power
measurements. For example, electronics equipment powered by switching power supplies typically
produces odd harmonics up to the 21st. To ensure that the harmonics are properly addressed, EPA
recommends the use of a watt meter with frequency response of at least 3 kHz. This will account for
harmonics up to the 50th, which is recommended by IEC 555.
Resolution
Manufacturers should choose a watt meter that can provide resolution of 0.1 watt.
Accuracy
Catalogues and specification sheets for watt meters typically provide information on the accuracy of power
readings that can be achieved at different range settings. If the power measurement is very close to the
energy-efficiency guideline specified in the MOU, a test procedure with greater accuracy will be necessary.
For example, if the E
NERGY
S
TAR
specification is 1.0 watt or less and the resulting accuracy of the watt
meter at the test settings is ± 0.1 watts, then a power measurement of less than 0.9 watts will ensure that
the product is compliant. Testing Guidelines (Protocol) for E
NERGY
S
TAR
®
Qualified Set-Top Boxes - July 2000
4
Calibration
To maintain their accuracy, watt meters should be calibrated every year with a standard that is traceable to
the U.S. National Bureau of Standards (NBS).
III.
T
EST
M
ETHOD
Following are the test steps for measuring the true power requirements of the test unit in standby/low-
power mode:
1. Power on all test equipment and properly adjust operation range.
2. Connect the test equipment and unit under test.
3. Check for normal operation of the test unit and leave all customer adjustment to factory default
settings (i.e., unit must be in the condition shipped to the customer). In addition, if a product is
designed for a network environment, it must be tested while connected to the network to ensure
that all power consumption and performance criteria are met.
4. Bring the test unit into standby/low-power mode (not disconnect mode) either by using the remote
control device or by using the ON/OFF switch on the test unit cabinet.
5. Either verify that the wall outlet power is within specifications or adjust the AC power source
output as described in Section I (e.g., 115Vrms ± 3Vrms, 60Hz ± 3Hz).
6. Set the power meter current range. The selected full scale value multiplied by the crest factor
rating (Ipeak/Irms) of the meter must be greater than the peak current reading from the
oscilloscope.
7. After the unit under test reaches operating temperature and the readings on the power meter
stabilize (approximately 90 minutes), take the true power reading in watts from the power meter.
8. Record the test conditions and test data. The measurement time shall be sufficiently long to
measure the correct average* value to within a +10% - 0% error. If the device has different
standby/low-power modes that can be manually selected, the measurement should be taken with
the device in the most power consumptive mode. If the modes are cycled through automatically,
the measurement time should be long enough to obtain a true average that includes all modes.
* The power consumption measurement will be continued for 24 hours and averaged or until the
time period where averaged power consumption can be accurately measured. The time period for
testing an individual model is based up