ARL-TN-0723 ● DEC 2015

US Army Research Laboratory

Liquid-Crystal Display (LCD) Screen Thermal 

Testing to Simulate Solar Gain

by Steven Callaway

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ARL-TN-0723 ● DEC 2015

US Army Research Laboratory

Liquid-Crystal Display (LCD) Screen Thermal 

Testing to Simulate Solar Gain

by Steven Callaway

Computational and Information Sciences Directorate, ARL

Approved for public release; distribution is unlimited.
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1. REPORT DATE (DD-MM-YYYY)

December 2015

2. REPORT TYPE

Final

3. DATES COVERED (From - To)

09/2013

4. TITLE AND SUBTITLE

Liquid-Crystal Display (LCD) Screen Thermal Testing to Simulate Solar Gain

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Steven Callaway

5d. PROJECT NUMBER

R.0013587.1

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

US Army Research Laboratory

ATTN: RDRL-CII-B

2800 Powder Mill Road

Adelphi, MD 20783-1138

8. PERFORMING ORGANIZATION REPORT NUMBER

ARL-TN-0723

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)

11. SPONSOR/MONITOR'S REPORT NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

The Boland View Port 20 inch liquid-crystal display (LCD) monitor was tested in order to determine a solution to failures 

observed when the monitor was used outdoors. In direct sunlight, screen temperatures went beyond the maximum operational 

temperature, causing the image to “white out.” Tests were first performed to determine the monitor’s baseline operations and 

maximum screen temperature before failure. A temperature chamber and heat lamp were used to simulate worst-case 

conditions. The next tests were performed outdoors to determine possible solutions to problem. In separate tests, the metal 

frame and the screen of the monitor were shaded from the sun, eliminating the solar loading from each area. Results were the 

most promising when the screen was shaded from the sun. After observing this behavior Hot Mirror glass from Dicrotec Thin 

Films was tested. This glass uses a coating that passes visible light, but reflects infrared light, reducing the total heat 

transmitted to the monitor from the sun. Satisfactory results were achieved when a 1 inch air gap was maintained between the 

monitor and glass. These results lead to several design recommendations to eliminate the failures previously observed with the 

Boland monitor.

15. SUBJECT TERMS

Liquid crystal display, LCD, Solar, Thermal, Infrared

16. SECURITY CLASSIFICATION OF:

17. LIMITATION

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 ABSTRACT

UU

18. NUMBER

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 PAGES

34

19a. NAME OF RESPONSIBLE PERSON

Steven Callaway

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

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19b. TELEPHONE NUMBER (Include area code)

301-394-1152

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Prescribed by ANSI Std. Z39.18
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iii

Contents

List of Figures iv

List of Tables v

Summary 1

1. Introduction 3

2. Methods, Assumptions, and Procedures 3

2.1 Test 1 – 90 °F Ambient Temperature 5

2.2 Test 2 – Bench Test with a 250 W Heat Lamp 5

2.3 Test 3 – Outdoors Under Direct Sunlight 8

2.4 Test 4 – Outdoors Under Direct Sunlight, Monitor Frame Covered 8

2.5 Test 5 – Outdoors Under Direct Sunlight, Monitor Screen Covered 9

2.6 Test 6 – Bench Test with a 250 W Heat Lamp and Hot Mirror Glass 9

2.7 Test 7 – Bench Test with a 250 W Heat Lamp and Hot Mirror Glass, 

1 Inch Air Gap 10

3. Results and Discussions 10

3.1 Test 1, Environmental Chamber, 90 °F Ambient 10

3.2 Test 2, Bench, 250 W Heat Lamp Above Screen 12

3.3 Test 3, Outdoors, Direct Sunlight 14

3.4 Test 4, Outdoors, Direct Sunlight, Frame Covered 15

3.5 Test 5, Outdoors, Direct Sunlight, Screen Covered 17

3.6 Test 6, 250 W Heat Lamp, Glass on Monitor 19

3.7 Test 7, 250 W Heat Lamp, Glass with 1 Inch Air Gap 20

4. Conclusions and Recommendations 22

5. References 25

Distribution List 26
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iv

List of Figures

Fig. 1 Front view of the View Port 20 inch HD/SD DayBrite Monitor...........4

Fig. 2 Rear view of the View Port 20 inch HD/SD DayBrite Monitor............4

Fig. 3 Test image used on Boland View Port 20 inch LCD monitor...............4

Fig. 4 Position of the sun relative to the monitor during the hottest part of the 

day..........................................................................................................6

Fig. 5 View factor diagram ..............................................................................7

Fig. 6 Spectral scan results of Hot Mirror glass used from Dicrotec Thin 

Films ......................................................................................................9

Fig. 7 Thermocouple locations for Test 1 ......................................................11

Fig. 8 Temperature vs. time for Test 1 during the steady state period of the 

test........................................................................................................11

Fig. 9 Difference between screen temperature and ambient through the steady 

state period of Test 1............................................................................12

Fig. 10 Thermocouple locations for Test 2 ......................................................12

Fig. 11 Temperature vs. time for Test 2 during the steady-state period of the 

test........................................................................................................13

Fig. 12 Difference between screen temperature and ambient through the 

steady-state period of Test 2 ................................................................13

Fig. 13 Thermocouple locations for Test 3 ......................................................14

Fig. 14 Temperature vs. time for Test 3 during the steady-state period of the 

test........................................................................................................14

Fig. 15 Difference between screen temperature and ambient through the 

steady-state period of Test 3 ................................................................15

Fig. 16 Thermocouple locations for Test 4 ......................................................16

Fig. 17 Temperature vs. Time for Test 4 during the steady-state period of the 

test........................................................................................................16

Fig. 18 Difference between screen temperature and ambient through the steady 

state period of Test 4............................................................................17

Fig. 19 Thermocouple locations for Test 5 ......................................................18

Fig. 20 Temperature vs. time for Test 5 during the steady-state period of the 

test........................................................................................................18

Fig. 21 Difference between screen temperature and ambient through the steady 

state period of Test 5............................................................................19

Fig. 22 Thermocouple locations for Test 6 ......................................................19

Fig. 23 Temperature vs. time for Test 6...........................................................20
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v

Fig. 24 Thermocouple locations for Test 7 ......................................................21

Fig. 25 Temperature vs. time for Test 7 during the steady-state period of the 

test........................................................................................................21

Fig. 26 Difference between screen temperature and ambient through the steady 

state period of Test 7............................................................................22

List of Tables

Table 1 Channel averages for Test 1 during the steady state period of the 

test........................................................................................................11

Table 2 Channel averages for Test 2 during the steady-state period of the 

test........................................................................................................13

Table 3 Channel averages for Test 3 during the steady-state period of the 

test........................................................................................................15

Table 4 Channel averages for Test 4 during the steady-state period of the 

test........................................................................................................16

Table 5 Channel averages for Test 5 during the steady-state period of the 

test........................................................................................................18

Table 6 Channel averages for Test 7 during the steady-state period of the 

test........................................................................................................21

Table 7 Test result overview.............................................................................22
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vi

INTENTIONALLY LEFT BLANK.
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1

Summary

Testing completed on the Boland View Port 20 inch liquid-crystal display (LCD)

monitor was motivated by a customer request to solve a problem. The equipment 

to be tested was being used as a teleprompter screen in both indoor and outdoor 

settings. In both situations, the screen is positioned on its back, elevated roughly 

9 inches from the ground. The area perpendicular to the screen is covered by a 

decorative shroud, used to obscure the screen during formal occasions. When the 

equipment is being used outdoors on hot summer days, ambient temperatures meet 

or exceed 90 °F. The monitor is subject to direct sunlight during the hottest part of 

the day as the sun is directly overhead. Under these conditions, the customer noted 

images would “white out,” making characters difficult to read. These malfunctions 

rendered the system unusable. 

The testing performed set out to replicate these conditions and recommend an area 

of design improvement. A temperature chamber and heat lamp, as well as outdoor 

testing, were used to simulate thermal loading on the screen. Different 

configurations were then explored as solutions to help eliminate the solar loading 

on the monitor. For each test, various temperatures were recorded on the monitor 

using a Graphtec Midi Logger GL220 data logger. Internal exhaust fans on the 

monitor were set to high for each test, as they would be under normal warm weather 

conditions.

The first test involved placing the monitor in a heat chamber set to 90 °F. This was 

meant to simulate the operation of the monitor on a hot summer day in the absence 

of solar loading. It offered a baseline operation temperature for the system. The 

screen temperature was found to operate at an average of 1.70 °F above ambient. 

The second test performed used a 250 W heat lamp suspended above the monitor 

to simulate solar loading. The test was performed on a lab bench at room 

temperature because of space constraints in the heat chamber. The screen developed 

a temperature 75 °F above ambient, averaged at 146.2 °F. Screen failure was 

observed at 140 °F, which set the maximum allowable temperature for the screen. 

Test 3 was performed outdoors in direct sunlight. With an intermittent breeze and 

changing sunlight conditions, the screen reached an average temperature of 62.6 °F 

above ambient. This test provided baseline numbers for comparison to later results.

Test 4 was performed outdoors in direct sunlight with the metal frame of the 

monitor shielded from the sun. By comparing the results of this test to Test 3, the 

contributions of the solar gain through the monitor frame could be analyzed. The 
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2

screen reached an average temperature of 56.8 °F above ambient, 5.8 °F lower than 

the 62.6 °F rise over ambient observed without the frame shaded.

For Test 5 the monitor was again placed outside in direct sunlight, this time with 

the screen surface shielded from the Sun. By comparing the results of this test to 

Test 3, the contributions of the solar gain through the screen surface could be 

analyzed. The screen reached an average temperature of 23.3 °F above ambient, 

39.3 °F lower than the 62.6 °F rise over ambient observed without the frame shaded.

With the results from Test 5, is was determined that shielding the screen from solar

gains was the best way to avoid monitor failure. In order to accomplish this Hot 

Mirror glass from Dicrotec Thin Films was tested. The Hot Mirror glass features a 

glass substrate with a coating on one side that reflects infrared light and passes 

visible light. This allows the teleprompter image to be read clearly through the glass 

while the heat is reflected away from the monitor. 

Test 6 examined the function of the Hot Mirror glass. The monitor was positioned 

on a lab bench with the 250 W heat lamp positioned above it to simulate solar 

loading. The Hot Mirror glass was placed on the top surface of the monitor. With 

this configuration screen failure was observed, as the screen temperature reached 

and exceeded 140 °F. This was due to the positioning of the Hot Mirror glass. With 

the glass placed directly on top of the monitor, it trapped any heat that was 

developed by the screen itself. 

For Test 7 the Hot Mirror glass was spaced away from the monitor to leave a 

1 inch air gap between the glass and screen. The monitor was again positioned on 

a lab bench with the 250 W heat lamp positioned above it to simulate solar loading.

With this arrangement, heat developed by the monitor was able to convect out of 

the monitor and away from underneath the glass. The screen developed a 54.65 °F

rise over ambient, approximately a 20 °F improvement over the results from 

Test 2.

Following the results of these tests several recommendations were made. An air 

gap needs to be maintained between the Hot Mirror glass and Boland monitor, fans 

should be used to prevent any heat from being trapped beneath the glass, and the 

glass needs to be thermally insulated from the fixture and monitor. 

With these recommendations taken into account the issues with the Boland View 

Port 20 inch LCD monitor can be resolved.
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3

1. Introduction

The motivation for the thermal testing performed in this report was brought on by 

customer difficulties with the failure of a Boland View Port 20 inch LCD monitor. 

The monitor is used outdoors as a teleprompter screen. The monitor is positioned 

face up on the floor of a stage, while the screen image is reflected to a viewing 

screen in front of the speaker. 

Failure was only observed on hot summer days under direct sunlight. It was 

especially prevalent during the hottest part of the day, when the sun was at its 

highest point. The customer observed that the LCD screen began to “white out” and 

the characters became illegible. 

Testing conditions set out to simulate these conditions in the most accurate way 

possible. A temperature chamber, heat lamp, and outdoor testing setup were all 

used in different configurations to perform 5 different tests. The test scenarios 

covered conditions in 90 °F ambient temperatures, screen failure under simulated 

solar loading, direct sunlight outdoors, conditions with the monitor frame shaded 

in direct sunlight, and conditions with the LCD screen shaded in direct sunlight.

Hot Mirror glass from Dicrotec Thin Films, which has a coating that passes visible 

light and reflects infrared light, was also tested as a possible solution to the 

problems experienced with the monitor.

2. Methods, Assumptions, and Procedures

In order to determine the mode of failure for the Boland monitor, several tests were 

performed. Several different configurations were used to simulate the normal 

working conditions of the monitor, including using a temperature chamber, using a 

heat lamp, and taking advantage of natural sunlight.

The View Port 20 inch HD/SD DayBrite Monitor (Model Number DHD 20W DB) 

features metal chassis measuring 19 inches x 11.63 inches x 2.25 inches. The 

chassis includes a 20 inch screen with a user adjustable 4:3 or 16:9 aspect ratio. The 

chassis is also equipped with 2 exhaust fans used to circulate and exhaust air from 

the chassis. The DayBrite Monitor features SDI, Composite, VGA, and DVI inputs 

to accommodate various configurations. Figures 1 and 2 show the front and rear 

views of the monitor.
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Fig. 1 Front view of the View Port 20 inch HD/SD DayBrite Monitor

Fig. 2 Rear view of the View Port 20 inch HD/SD DayBrite Monitor

During each test, an image needed to be displayed on the screen to best simulate 

the function of a teleprompter. Figure 3 shows the image that was used. The use of 

a black background with white text was important in creating the worst-case 

scenario for the absorption of solar radiation.

Fig. 3 Test image used on Boland View Port 20 inch LCD monitor

To assess the performance and failure of the DayBrite Monitor, 7 tests were 

performed. They included running the monitor in 90 °F ambient temperature, under 
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5

a 250 W heat lamp, outdoors in direct sunlight, outdoors in direct sunlight with the 

frame covered, and outdoors in direct sunlight with the screen covered. Hot Mirror 

glass was also evaluated as a possible solution to the problem. For each test, the 

monitor was positioned in a similar fashion with the internal fans set to high. This 

served to create consistency between the tests and to simulate real-world 

conditions. A Graphtec Midi Logger GL220 data logger was used for each test to 

record pertinent temperatures so that the result of each test could be compared and 

contrasted.

2.1 Test 1 – 90 °F Ambient Temperature

The first test performed was to place the monitor in a 90 °F ambient condition with 

no solar loading. This test determined the base line conditions of the monitor under 

worst-case ambient temperatures. Using a heat chamber, the temperature was set to 

hold at 90 °F after the monitor was in place. 

To ensure even heating of the monitor, it was placed in the center of the floor of the 

chamber. Using Delrin blocks, the monitor was elevated 1 inch from the floor of 

the chamber. This allowed for air flow into and out of the monitor and prevented 

heat from conducting into the monitor from the walls of the chamber.

After the test was performed, the temperature rise over ambient of the screen was 

analyzed. This determined how much heat is generated by the monitor under normal 

operation.

2.2 Test 2 – Bench Test with a 250 W Heat Lamp

For Test 2, a 250 W heat lamp was used to simulate the solar loading from the sun 

on the monitor. The heat from the sun can be approximated using the solar constant, 

Sc,, which is an average measurement of the heat flux from the sun, measured by 

satellites outside of the Earth’s atmosphere. As a rough approximation, it is 

assumed that 30% of the heat from the sun is reflected or absorbed by the Earth’s 

atmosphere, and 70% of the heat travels to the Earth’s surface. 

To demonstrate the effect of the relationship of the location of the sun relative to 

the monitor, Lambert’s Cosine Law is used. It says that there is a proportional 

relationship between the cosine of the angle of the normal vectors between 2

surfaces and the intensity of the radiation.2 At the hottest part of the day, the angle 

between vectors normal to the surface of the sun and monitor is 0°, as shown in 

Fig. 4.

GGSS,OO = SSCC ∙ cos(θθ) (1)
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where SSCC = SSSSSSSSSS CC CCCCCC CCCC = 433.66 BBBBBB

hrr ff 2 

 θθ = AA AA AA ss ss nn SS = 0 ̊

GGSS,OO = 433.66

BB

h ff 2 ∙ cos(0 ̊)

GGSS,OO = 433.66

BB

h ff 2

Fig. 4 Position of the sun relative to the monitor during the hottest part of the day

Assuming that 70% of the solar radiation penetrates the Earth’s atmosphere,

qq heeee ee eeeeeeee = .70 ∙ GGSS,OO ∙ AAss ss (2)

wwh GGSS,OO = 433.66

BB

h ff 2

AAss ss = 11.75 ii xx 19 ii = 223.25 ii 2 = 1.55 ff 2

qq heeee ee eeeeeeee = .70 ∙ 433.66

BB

h ff 2 ∙ 1.55 ff 2

qq heeee ee eeeeeeee = 470.52

BB

h

Once the theoretical solar loading on the monitor was obtained, it needed to be 

recreated in the lab setting. The 250 W heat lamp was positioned over the monitor 

so that it created an equivalent heat transfer rate. To determine this position, the 

view factor between the surface of the lamp and the surface of the monitor was 

calculated. The view factor (Fij) is best described as the “fraction of the radiation 
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7

leaving surface i that is intercepted by surface j”.1 Figure 5 shows the positioning 

and variables used to calculate the view factor. 

Fig. 5 View factor diagram

FFii = ��WWii+WWjj�

2

+4�

1

2−��WWjj−WWii�

2

+4�

1

2

2WWii

(3)

wwh WW = ww

LL aa WW = wwLL

ww = 4.875 in

ww = 19.000 in

L = 14.221 in

FFii =

�� 4.875 ii

14.221 ii + 19.000 ii

14.221 ii �

2

+ 4�

1

2

− �� 4.875 ii

14.221 ii − 19.000 ii14.221 ii �

2

+ 4�

1

2

2 ∙ 4.875 ii

14.221 ii

FFii = .552

Multiplying the heat from the 250 W heat lamp ( qq llll) by the view factor (FFii) 

gives the amount of heat transmitted to the screen:

1

qqss ss = qq llll ∙ FFii (4)

wwh qq llll = 250 WW = 853

BB

h

FFii = .552
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8

qqss ss = 853

BB

h ∙ .552

qqss ss = 470.856

BB

h

It can be seen that the theoretical solar loading of the monitor and the loading due 

to the 250 W heat lamp are similar. By positioning the heat lamp 14.221 inches 

away from the monitor, the same heat transfer rate of 470.856 BBBBBB

hrr is achieved.

3

With the configuration determined, the monitor was placed on a lab bench with the 

same 1 inch Delrin blocks elevating the monitor from the table surface. The

250 W heat lamp was then positioned approximately 14.221 inches above the 

screen. This distance allowed the heat to be spread across the entire screen while 

still maintaining the necessary intensity. The test was performed outside of the heat 

chamber due to space constraints. 

The temperature of the screen was closely monitored to determine the exact 

temperature at which the image began to fail. 

2.3 Test 3 – Outdoors Under Direct Sunlight

Test 3 was performed outdoors in direct sunlight. The monitor was again placed on 

1 inch Delrin blocks to allow for adequate airflow around the monitor. The test 

continued until the monitor reached a relatively steady-state, though this was

difficult with changing sun throughout the day and an intermittent breeze. 

The temperature rise of the screen over the ambient temperature was again 

analyzed. This dataset served as a baseline for comparison to later results. 

2.4 Test 4 – Outdoors Under Direct Sunlight, Monitor Frame 

Covered

The fourth test performed on the monitor was completed outdoors in direct sunlight. 

A fixture was fabricated to shade the metal screen on the monitor from the sunlight, 

while leaving an adequate air gap for natural convection out of the frame. The 

monitor was placed on 1 inch Delrin blocks to allow for airflow around the monitor.

The data collected were compared to the results in Test 3 to determine if shading 

the monitor frame from the sun was a sufficient solution. 
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9

2.5 Test 5 – Outdoors Under Direct Sunlight, Monitor Screen 

Covered

Test 5 was performed in direct sunlight with the screen shaded from the sun. An air 

gap was left under the fixture to allow for convection at the screen. The monitor 

was again placed on 1 inch Delrin blocks to allow for airflow around the monitor.

The data collected were compared to results from Test 3 to determine if shading the 

monitor screen from the Sun was a sufficient solution.

2.6 Test 6 – Bench Test with a 250 W Heat Lamp and Hot Mirror 

Glass

After the completion of Test 5, it was clear that in order to eliminate the solar 

loading that was causing the monitor to fail, the screen needed to be shielded from 

the sun. In order to accomplish this Hot Mirror glass from Dicrotec Thin Films was 

used. Hot Mirror glass consists of a glass substrate that is coated on 1 side. The 

coating passes visible light, but reflects the infrared component of the light back to 

its source. Infrared light, with a wavelength from about 700 nm to 1 mm, carries 

the majority of the heat that the Earth receives from the sun. 

Figure 6 shows the spectral scan results of the Hot Mirror glass used. It can be seen 

that 90% to 95% visible light, which exists in the 300 and 700 nm range, is passed 

through the glass. However, from 700 to 1100 nm, the infrared light is almost 

completely reflected. 

Fig. 6 Spectral scan results of Hot Mirror glass used from Dicrotec Thin Films

Test 6 was performed on a lab bench at room temperature. A 250 W heat lamp was 

used to simulate solar loading, positioned above the screen at a distance that 
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10

allowed the heat to be spread across the entire screen while still maintaining the 

necessary intensity. A piece of the Hot Mirror glass large enough to cover the entire 

monitor was placed directly on the top side of the monitor in order to shield the 

monitor from the solar loading.

2.7 Test 7 – Bench Test with a 250 W Heat Lamp and Hot Mirror 

Glass, 1 Inch Air Gap

Test 7 was performed on a lab bench at room temperature. A 250 W heat lamp was 

used to simulate solar loading, positioned above the screen at a distance that 

allowed the heat to be spread across the entire screen while still maintaining the 

necessary intensity. A piece of the Hot Mirror glass large enough to cover the entire 

monitor was placed on the top side of the monitor with a 1 inch air gap between the 

monitor and glass. This configuration allowed for the infrared heat to be reflected 

away from the top side of the glass, while allowing heat generated by the monitor 

to escape from underneath the glass. 

3. Results and Discussions

For each test thermocouples were positioned on the monitor as shown. Channel 1 

was used to record the ambient temperature in each test. A graph was generated to 

show the steady state conditions for each test. The average temperature throughout 

that time period is also calculated. 

3.1 Test 1, Environmental Chamber, 90 °F Ambient

The DayBrite Monitor was placed in a temperature chamber that maintained an 

ambient temperature of 90 °F. With the internal fans set to high, the monitor was 

positioned to allow for adequate airflow around the monitor. Thermocouples were 

placed along the rear of the monitor, as well as along the front frame and at the 

center of the screen (Fig. 7). The temperature for each channel during the steadystate portion of the test can be seen in Fig. 8, and the average channel values can be 

seen in Table 1.

Thermocouple Locations:

1. Ambient
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11

Fig. 7 Thermocouple locations for Test 1

Fig. 8 Temperature vs. time for Test 1 during the steady state period of the test

Table 1 Channel averages for Test 1 during the steady state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7

92.0 93.0 88.4 92.9 90.1 93.7 89.6

The results show minimal heat generation by the monitor in the absence of solar 

loading. The temperature of the screen surface maintained an average rise of 

1.70 °F above ambient during the steady-state period (Fig. 9). 

87

88

89

90

91

92

93

94

95

10000 20000 30000 40000 50000

Temp (F)

Time (s)

Test 1

90 °F Ambient

CH1

CH2

CH3

CH4

CH5

CH6

CH7
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Average Difference: 1.70 °F

Fig. 9 Difference between screen temperature and ambient through the steady state period 

of Test 1

3.2 Test 2, Bench, 250 W Heat Lamp Above Screen

The DayBrite Monitor was placed on a lab bench with a 250 W heat lamp 

positioned above the screen. With the internal fans set to high, the monitor was 

positioned to allow for adequate airflow around the monitor. Thermocouples were 

placed along the rear of the monitor, as well as along the front frame and at the 

center of the screen (Fig. 10). The temperature for each channel during the steadystate portion of the test can be seen in Fig. 11, and the average channel values can 

be seen in Table 2.

Thermocouple Locations:

1. Ambient

 

Fig. 10 Thermocouple locations for Test 2

0

1

2

3

10000 15000 20000 25000 30000 35000 40000 45000 50000

Degrees F

Time (s)

Test 1

Channel 6 Rise Above Ambient
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Fig. 11 Temperature vs. time for Test 2 during the steady-state period of the test

Table 2 Channel averages for Test 2 during the steady-state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7

71.3 98.2 94.2 94.0 91.5 146.2 92.1

The simulated solar loading created a 75.0 °F rise over ambient at the center of the 

screen (Fig. 12). Screen failure was observed at 140 °F.

Average Difference: 75.0 °F

Fig. 12 Difference between screen temperature and ambient through the steady-state period 

of Test 2

70

80

90

100

110

120

130

140

150

4900 5000 5100 5200 5300 5400

Temp (F)

Time (s)

Test 2

Lab Bench, 250 W Heat Lamp

CH1

CH2

CH3

CH4

CH5

CH6

CH7

72

74

76

4900 5000 5100 5200 5300 5400

Degrees F

Time (s)

Test 2

Channel 6 Rise Above Ambient
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3.3 Test 3, Outdoors, Direct Sunlight

The DayBrite Monitor was placed outside in direct sunlight. With the internal fans 

set to high, the monitor was positioned to allow for adequate airflow around the 

monitor. Thermocouples were placed along the rear of the monitor, as well as along 

the front frame and at the center of the screen. Thermocouple 9 was placed on the 

exhaust fan outlet on the rear of the monitor (Fig. 13). The temperature for each 

channel during the steady state portion of the test can be seen in Fig. 14, and the 

average channel values can be seen in Table 3.

Thermocouple Locations:

1. Ambient

 

Fig. 13 Thermocouple locations for Test 3

Fig. 14 Temperature vs. time for Test 3 during the steady-state period of the test

60

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

1500 1700 1900 2100 2300 2500 2700 2900

Temp (F)

Time (s)

Test 3

Outdoors, Direct Sunlight

CH1

CH2

CH3

CH4

CH5

CH6

CH7

CH8

CH9
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Table 3 Channel averages for Test 3 during the steady-state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9

71.8 100.5 93.2 97.1 103.6 130.9 108.7 134.4 97.4

At the conclusion of the test, a 62.6 °F rise over ambient was observed at the screen

(Fig. 15). It should be noted that the test was performed during September, a time 

of the year when the sun is not at its most intense. There was also a slight breeze, 

which contributed to lower screen temperatures. 

Average Difference: 62.6 °F

Fig. 15 Difference between screen temperature and ambient through the steady-state period 

of Test 3

3.4 Test 4, Outdoors, Direct Sunlight, Frame Covered

The DayBrite Monitor was placed outside in direct sunlight. With the internal fans 

set to high, the monitor was positioned to allow for adequate airflow around the 

monitor. Thermocouples were placed along the rear of the monitor, as well as along 

the front frame and at the center of the screen. Thermocouple 9 was placed on the 

exhaust fan outlet on the rear of the monitor (Fig. 16). The front frame of the 

monitor was shaded from the sun to analyze the contribution of the solar gains 

through the monitor frame to the screen temperature. The temperature for each 

channel during the steady-state portion of the test can be seen in Fig. 17, and the 

average channel values can be seen in Table 4.

55

60

65

70

1500 1700 1900 2100 2300 2500 2700 2900

Degrees F

Time (s)

Test 3 

Channel 6 Rise Above Ambient
Approved for public release; distribution is unlimited.

16

Thermocouple Locations:

1. Ambient

 

Fig. 16 Thermocouple locations for Test 4

Fig. 17 Temperature vs. Time for Test 4 during the steady-state period of the test

Table 4 Channel averages for Test 4 during the steady-state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9

72.5 92.4 88.5 90.4 91.3 125.9 87.3 129.2 91.8

At the conclusion of the test, an average rise over ambient of 56.8 °F was observed 

at the screen (Fig. 18). It should be noted that the test was not performed during a 

part of the year that the sun was at its most intense. There was also a slight breeze, 

which contributed to lower screen temperatures. When compared to the results of 

Test 3, where a 62.6 °F rise over ambient was observed in direct sunlight, it can be 

60

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

1200 1300 1400 1500 1600 1700 1800

Temp (F)

Time (s)

Test 4 

Outdoors, Frame Covered

CH1

CH2

CH3

CH4

CH5

CH6

CH7

CH8

CH9
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17

seen that the solar gains through the monitor frame have a small contribution to the 

overall temperature of the screen.

Average Difference: 56.8 °F

Fig. 18 Difference between screen temperature and ambient through the steady state period 

of Test 4

3.5 Test 5, Outdoors, Direct Sunlight, Screen Covered

The DayBrite Monitor was placed outside in direct sunlight. With the internal fans 

set to high, the monitor was positioned to allow for adequate airflow around the 

monitor. Thermocouples were placed along the rear of the monitor, as well as along 

the front frame and at the center of the screen. Thermocouple 9 was placed on the 

exhaust fan outlet on the rear of the monitor (Fig. 19). The screen was shaded from 

the sun to analyze the contribution of the solar gains through the screen to its overall 

temperature. The temperature for each channel during the steady-state portion of 

the test can be seen in Fig. 20, and the average channel values can be seen in 

Table 5.

50

52

54

56

58

60

62

1200 1300 1400 1500 1600 1700 1800

Degrees F

Time (s)

Test 4

Channel 6 Rise Above Ambient
Approved for public release; distribution is unlimited.

18

Thermocouple Locations:

1. Ambient

 

Fig. 19 Thermocouple locations for Test 5

Fig. 20 Temperature vs. time for Test 5 during the steady-state period of the test

Table 5 Channel averages for Test 5 during the steady-state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH9

91.0 97.3 95.9 103.4 118.8 114.4 102.0 103.5

At the conclusion of the test, an average rise over ambient of 23.3 °F was observed 

at the screen (Fig. 21). It should be noted that the test was not performed during a 

part of the year that the sun was at its most intense. There was also a slight breeze, 

which contributed to lower screen temperatures. When compared to the results of 

Test 3, where a 62.6 °F rise over ambient was observed in direct sunlight, it can be 

seen that the solar gains through screen are significant. 

75

80

85

90

95

100

105

110

115

120

125

3400 3500 3600 3700 3800

Temp (F)

Time (s)

Test 5

Outdoors, Screen Covered

CH1

CH2

CH3

CH4

CH5

CH6

CH7

CH9
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19

Average Difference: 23.3 °F

Fig. 21 Difference between screen temperature and ambient through the steady state period 

of Test 5

3.6 Test 6, 250 W Heat Lamp, Glass on Monitor

The DayBrite Monitor was placed on a lab bench with a 250 W heat lamp 

positioned above the screen. A piece of Hot Mirror glass was placed across the 

monitor so that its entire surface was covered. With the internal fans set to high, the 

monitor was positioned to allow for adequate airflow around the monitor. 

Thermocouples were placed along the front frame of the monitor and at the center 

of the screen. Temperatures were also monitored on the top and bottom sides of the 

glass (Fig. 22). The temperature for each channel during the test can be seen in 

Fig. 23.

Thermocouple Locations:

1. Ambient

 

Fig. 22 Thermocouple locations for Test 6

20

22

24

26

28

3400 3450 3500 3550 3600 3650 3700 3750 3800

Degrees F

Time (s)

Test 5

Channel 6 Rise Above Ambient
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20

Fig. 23 Temperature vs. time for Test 6

After approximately 3000 s, the screen temperature reached 140 °F. As the 

temperature continued to climb without reaching steady-state, the test was aborted.

3.7 Test 7, 250 W Heat Lamp, Glass with 1 Inch Air Gap

The DayBrite Monitor was placed on a lab bench with a 250 W heat lamp 

positioned above the screen. A piece of Hot Mirror glass was placed across the 

monitor so that its entire surface was covered. The glass was spaced 1 inch above 

the surface of the monitor to allow heat produced by the monitor to escape. With 

the internal fans set to high, the monitor was positioned to allow for adequate 

airflow around the monitor. Thermocouples were placed along the front frame of 

the monitor and at the center of the screen. Temperatures were also monitored on 

the top and bottom sides of the glass (Fig. 24). The temperature for each channel 

during the steady state portion of the test can be seen in Fig. 25, and the average 

channel values can be seen in Table 6.

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

145

150

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Temp (F)

Time (s)

Test 6

250 W Lamp, Glass on Monitor

CH1

CH3

CH4

CH6

CH7

CH8

CH9

CH10
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21

Thermocouple Locations:

1. Ambient

 

Fig. 24 Thermocouple locations for Test 7

Fig. 25 Temperature vs. time for Test 7 during the steady-state period of the test

Table 6 Channel averages for Test 7 during the steady-state period of the test

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH9

74.22 91.25 109.30 128.90 90.81 84.75 106.21 84.88

The screen temperature developed a steady-state average of 54.65 °F over ambient 

(Fig. 26). When compared to the results of Test 2, which produced a 75.0 °F rise 

over ambient at the screen, it can be seen that the Hot Mirror glass eliminated 

approximately 20 °F of temperature rise due to the simulated solar gain.

70

75

80

85

90

95

100

105

110

115

120

125

130

135

5000 5250 5500

Temp (F)

Time (s)

Test 7

250 W Lamp, Glass w 1" Air Gap

CH1

CH3

CH4

CH6

CH7

CH8

CH9

CH10
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22

Average Difference: 54.65 °F

Fig. 26 Difference between screen temperature and ambient through the steady state 

period of Test 7

4. Conclusions and Recommendations

Table 7 summarizes the test results. Detailed conclusions and recommendations 

follow.

Table 7 Test result overview

Test Description Average Degrees 

Above Ambient (F)

Test 1 90 °F ambient temp in chamber 1.70

Test 2 Bench Test, 250 W heat lamp 75.0

Test 3 Outdoors, Direct Sunlight 62.6

Test 4 Outdoors, Frame Covered 56.8

Test 5 Outdoors, Screen Covered 23.3

Test 6 Bench Test, 250 W heat lamp, hot mirror glass on monitor Screen failure

Test 7 Bench Test, 250 W heat lamp, hot mirror glass w 1” air gap 54.65

For Test 1 the environmental chamber was set to 90 °F to simulate a summer day 

in the shade. The monitor was placed in the chamber and allowed to come to steadystate. Various chassis temperatures as well as the screen temperature were recorded. 

The test showed that without solar loading the screen operates slightly above 

ambient temperature, with an average screen temperature 1.70 °F above ambient.

For Test 2 the monitor was placed on a lab bench with a 1 inch air gap below the 

body of the monitor. A 250 W heat lamp was placed 14.221 inches above the center 

of the screen to simulate intense solar loading. Various chassis temperatures and 

the screen temperature were again recorded. The screen image began to “white out”

54

54.2

54.4

54.6

54.8

55

55.2

55.4

5000 5250 5500

Degrees F

Time (s)

Test 7

Channel 6 Rise Above Ambient
Approved for public release; distribution is unlimited.

23

when the screen surface temperature rose above 140 °F. With the threshold for 

screen failure determined at 140 °F, the maximum operating conditions can be 

specified. Assuming an ambient temperature of 90 °F thermal loading can only 

cause a 50 °F rise before the monitor will fail. 

The monitor was then set outside in direct sunlight to determine natural solar 

loading with a more even distribution than a heat lamp can supply. The test resulted 

in a 62.6 °F average increase over ambient. Failure was not observed during either 

test, as the screen temperature only reached an average temperature of 130.9 °F. 

This can be attributed to a slight breeze outside as well as a reduced intensity of the 

sun because of the time of year.

The results while shading the metal frame from the sun were then tested. Average 

screen temperatures of 56.8 °F over ambient were observed. Screen temperatures 

averaged at 125.9 °F. These results would be very close to the threshold for failure 

on a hot summer day, especially if the increased intensity of the summer sun is 

considered.

The next scenario tested shielded the screen from the sun. Average screen 

temperatures of 23.3 °F over ambient was observed at an average screen 

temperature of 114.4 °F. This scenario offers the most promising results.

With these results Hot Mirror glass from Dicrotec Thin Films was then tested as a 

method to shield the screen from solar loading. The Hot Mirror glass uses a glass 

substrate with a coating on 1 side that passes visible light, but reflects infrared light. 

This eliminates the heat component of light from the sun while still maintaining the 

function of the teleprompter. 

The first test performed with the glass used the monitor on a lab bench with the 

250 W heat lamp positioned above it. The Hot Mirror glass was placed directly on 

top of the monitor in an attempt to shield the screen from the simulated solar 

loading. This test produced unsatisfactory results. With the Hot Mirror glass located 

on the top of the monitor, heat from the 250 W heat lamp was reflected away from 

the monitor. However, any heat that passed through the glass or that was generated 

by the monitor was trapped beneath the Hot Mirror glass by the same principle.

This caused the screen to fail, as temperatures climbed above 140 °F.

In order to mitigate this problem, the glass was then placed on top of the monitor 

with a 1 inch air gap. The air gap allows any heat generated by the monitor to 

escape, instead of being trapped underneath the glass. This test produced more 

satisfactory results, with an average rise of 54.65 °F over ambient at the screen. 
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These test results lend themselves to several design recommendations: maintaining 

an air gap between the Hot Mirror glass and the monitor, using fans to evacuate any 

heat trapped under the glass, and thermally insulating the glass from the monitor.

The results of Test 6 show that it is essential to maintain an air gap between the Hot 

Mirror glass and the monitor. The same characteristics of the glass that allow it to 

reflect solar gain also allow it to trap heat between the monitor and the glass. With 

an air gap between the glass and monitor, the heat will have an avenue of escape 

from the monitor and screen surface.

Using a small fan will also ensure that heat accumulated between the glass and 

monitor will not cause a failure. If placed inside the air gap between the monitor 

and glass, a series of small fans can be used to evacuate heat that may remain 

trapped underneath the glass. A multitude of small and quiet low voltage fans are 

available from commercial vendors. 

The results of Test 7 showed a substantial influx of heat in the Hot Mirror glass. 

The top side of the center of the glass reached a steady-state temperature of 

106.21 °F, approximately 32 °F above the average ambient temperature. The 

bottom side of the center of the glass reached a steady-state temperature of 

109.30 °F, approximately 35 °F above the average ambient temperature (see 

Table 6). With these results in mind, the glass needs to be thermally insulated from 

the fixture that holds it, as well as from the monitor itself. Otherwise, the heat will 

simply conduct from the glass to the monitor. 

With these recommendations taken into account, the issues caused by solar loading 

on the Boland View Port 20 inch LCD monitor can be resolved.
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5. References

1. Incropera Frank P, Dewitt David P, Bergman Theodore L, Lavine Adrienne S. 

Fundamentals of heat and mass transfer. 6th ed. Hoboken: John Wiley & Sons, 

2007.

2. Siegel Robert, Howell John R. Thermal radiation heat transfer. Washington, 

D.C.: Hemisphere Pub., 1992. 

3. Wong HY. Handbook of essential formulae and data on heat transfer for 

engineers. London: Longman, 1977.
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