# Presentation: 675406

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

## 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

- 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

## 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

- 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

- 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)

- 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/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 and Color Controls and Peripherals

## 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

- 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)

## 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

## Multiple Measurements

## 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

- Up to 30% variability by sample for some models

## Active Power Variability Among Different Voltages

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

## 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

- 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?