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ENERGY STAR Computer Monitor Test Methodology Craig Hershberg US EPA 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

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energy star computer monitor test methodology
ENERGY STAR Computer Monitor Test Methodology

Craig Hershberg


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?