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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
ENERGY STAR Computer Monitor Test Methodology

Craig Hershberg

US EPA

Hershberg.Craig@epa.gov

objectives of today s presentation
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
test methodology goals
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
development phase
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
removed references to three non energy factors
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)
retained two non energy factors
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
refresh rate
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)
luminance brightness
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
125 vs 175 cd m 2 for lcds
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
dark room conditions
Dark Room Conditions
  • Suggested by several members of industry for light measurements
  • References current industry norms through VESA FPDM Standard 2.0
color controls and peripherals
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)
addressing dvi inputs and digital monitors
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
data variability analysis
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
active power variability among different samples
Active Power Variability Among Different Samples
  • Up to 30% variability by sample for some models
active power variability among different voltages
Active Power Variability Among Different Voltages
  • Less than 4% variability by voltage for majority of models
reduced number of measurements per model
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
questions for industry
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?