Energy star computer monitor test methodology
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ENERGY STAR Computer Monitor Test Methodology Craig Hershberg US EPA Hershberg.Craig@epa.gov Objectives of Today’s Presentation Provide an overview of the final test methodology Share key points of discussion during the test methodology development phase, and their resolutions

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ENERGY STAR Computer Monitor Test Methodology

Craig Hershberg

US EPA

Hershberg.Craig@epa.gov


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Objectives of Today’s Presentation

  • Provide an overview of the final test methodology

  • Share key points of discussion during the test methodology development phase, and their resolutions

  • Present and gather industry input on two remaining issues regarding multiple measurements


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Test Methodology Goals

  • Develop sound procedure for testing computer monitors in On Mode; incorporate existing methodologies for Sleep and Off

  • Design a methodology that is comprehensive and produces repeatable test results

  • Decrease burden on manufacturers by referencing, where applicable, existing and widely used industry standards for testing

    • VESA

    • IEC


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Development Phase

  • Extensive input from stakeholders

    • Manufacturers, trade associations, European and Japanese stakeholders, TCO Development

  • Various drafts broadly distributed for comment during 9-month development phase

  • Final test methodology emailed to stakeholders in February 2003 – minor changes made since then

  • “Development Summary” captures key additions and changes that led to final methodology

    • Emailed to stakeholders and available on Web site

    • Basis for today’s presentation



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Removed References to Three Non-Energy Factors

  • Three non-energy factors from Draft 1 have been removed from Draft 2

    • Defective pixels (no effect on power consumption)

    • Contrast ratio (VESA Flat Panel Display Measurements (FPDM) Standard 2.0 does not define parameters for measuring contrast ratio)

    • Warranty (market-specific so hard to implement and police for global products like computer monitors)


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Retained Two Non-Energy Factors

  • Two non-energy factors originally included in Draft 1 of the specification have been moved to the test methodology

    • Refresh rate

    • Luminance (brightness)

  • Ensure all computer monitors are being tested under similar conditions


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Refresh Rate

  • Different refresh rates given for LCDs and CRTs, to accommodate differences in technologies

  • LCDs: Measured at 60 Hz, unless a different refresh rate is specifically recommended by the manufacturer

  • CRTs: Measured at 75 Hz (long-time norm in North America)

    • Discussion over use of 75 Hz or 85 Hz, which is consistent with TCO ’99 and general practice in Europe

    • 75 Hz chosen because most appropriate for power measurement purposes, whereas 85 Hz better for ergonomic purposes (reduces flicker, but increases power consumption)


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Luminance (Brightness)

  • Levels chosen that support the implementation of a performance-based specification

    • Allow for comparisons of power use between computer monitors when providing the same visual experience for the user

  • CRTs: Measured at minimum of 100 candelas per square meter (cd/m2)

  • LCDs: Measured at minimum of 175 cd/m2

    • Higher than CRTs because 100 candelas per square meter is much easier for LCDs to attain than for CRTs

  • All luminance test patterns borrowed from VESA FPDM Standard 2.0


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125 vs. 175 cd/m2 for LCDs

  • 125 cd/m2: Not selected because it would unfairly advantage models that only have brightness control, or operate in digital mode

    • Adjusting brightness to get 125 cd/m2 may lower power consumption by reducing power to backlights, allowing these models to qualify more easily

  • Maximum brightness: Not chosen because it may punish better performing models with a high brightness range, to allow for some degradation over time



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Dark Room Conditions

  • Suggested by several members of industry for light measurements

  • References current industry norms through VESA FPDM Standard 2.0


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Color Controls and Peripherals

  • All color controls and peripherals should be placed at factory default settings

    • No external devices should be connected to any USB hubs/ports

    • Any built-in peripherals should be set to off, or placed in their minimum power configuration (as adjustable by the user)

    • Circuit removal or similar actions not under user control may not be undertaken (e.g., removal of built-in speakers)



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Addressing DVI Inputs and Digital Monitors

  • Added a clarifying statement re: stable power measurements in Off Mode

    • Test methodology for all three operating modes states that power measurements should be taken once the power readings are stable

    • Power readings never quite stabilize due to DVI input check cycle

    • For models with DVI inputs, manufacturers should ignore the DVI input check cycle when measuring power consumption in Off

  • Included information on how to test digital only interface monitors

    • Monitors with both analog and digital interfaces should be tested in analog interface

    • See footnote 1



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Data Variability Analysis

  • First round of testing: Requested testing of 5 units at each of 3 different voltage/frequency combinations

    • 100 Volts/50 Hz, 115 Volts/60 Hz, 230 Volts/50 Hz

  • Data analysis: Considered the variability of manufacturers’ test data provided at each of the voltage/frequency combinations

  • Findings: 1) Much greater variation by sample than by voltage; 2) In On Mode, power use was often higher at 115 than 230; and 3) More data points submitted by manufacturers at 115 than other voltages


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Active Power Variability Among Different Samples

  • Up to 30% variability by sample for some models


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Active Power Variability Among Different Voltages

  • Less than 4% variability by voltage for majority of models


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Reduced Number of Measurements per Model

  • Second round of testing: Requested that interested manufacturers only test 3 units at 115 Volts/60 Hz

  • Overall testing reduced from 15 data points per model to 3 data points per model


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Questions for Industry

  • Does industry agree that testing at only one voltage/frequency combination is sufficient?

    • And if so, does it make sense to test at 115 Volts/60 Hz, as proposed in Draft 2?

    • Another option is to test at the voltage/frequency combination of the country where the monitor will be sold

    • Which option would industry prefer, and why?

  • Are there any manufacturer concerns with requiring three test units per model?

    • Do manufacturers have any other alternatives that they would like EPA to consider?