UV Test STrips - Guide to UV Measurement
Contents
1. rT lt O A gt a i o lt W q gt D E W 0 5 0 6 0 7 Extinction Decrement U E U Units Model Predicted Values Based on Op 2 Data 5 5 00 Error Values Linear Regression Model Upper 95 Conf Band Dec 0 03 EIT UV A Energy Density mJ cm 236 06 Lower 95 Conf Band oe ee ag Op 1 Data 8 17 00 Power Puck Lot 160298 R paoe Op 2 Data 5 5 00 Lot 260100 Op 2 Data 5 11 00 Lot 260100 Chart 3 Test strip extinction decrement data and model for Fusion F600 H bulb October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 20 The centerline in Chart 3 is the linear regression model based on Operator 2 s data taken on 5 5 2000 Operator 2 s data taken on 5 11 2000 was an attempt to validate the model The data represented by Operator 1 was overlaid in an attempt validate the model as well Operator 1 used test strips from lot 160248 Operator 2 used test strips from lot 260100 7 C ii_ Performance Limitations Operator 1 s data showed a similar non linear response to that observed on the Fusion D bulb when DEC exceeded 0 80 Operator 2 did not have data sufficiently past DEC 0 80 to suggest the same response The non linear response appears to be due to saturation when the extinction decrement reaches 0 80 Physical degradation blistering was not evident on any of the test strips The maximum UV2. measuring ar a UV sensitive for Tape Reader layer uncoated arca second sticker sticker possibility to fix double sided the strip on the belt After the tape has passed through the radiation source the optical density or extinction should be measured immediately Measurement of UV Intensity Structure and Functioning of the Dosimeter Measuring Instrument Brief Description Measuring principle Photometric transmitted light measurement of test strips i sensitive to UV radiation Light source 12v 16 W commercial halogen lamp Sensor UV selective photodiode max rel sensitivity 320 nm 50 rel sensitivity 300 360 nm Measuring transformer Aluminium block to support the halogen lamp photodiode and guidance for measuring tape with end stop Power 110 220v View to the surface of Dosimeter 773 248 0099 800 621 1296 888 UVLAMPS FAX 773 880 6647 800 99FAXUV UV FAXTS Service 773 880 6649 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips UV PROCESS SUPPLY INC CON TROL CURE RAD CHECK SYSTEM INSTRUCTION MANUAL PART M007 078 4 time as under 3 5 K factor provides a correction of deviations in different test strip batches 6 autom OFF time for the automatic switch off after the measurement has been completed 7 system check check of the electronic equipment Using the K factor The first batch of test strips has a density of 1 60 the second batc
3. Page 27 SOURCE EIT Inc 1998 UV PowerMAP and UV MAP Plus with PowerView Operator s Manual Sterling VA Author 12 Specifications Electrical Specifications Configuration 2 part Detachable Optics Head and UV Data Collector UDC Optics Head Supports optics to measure 4 spectral regions __ UDC 256 bytes non volatile memory uv Ranges _ High Power UVA B V 200mW cm to 20W cm UVC 20mWicm to 2Wicm Low Power UVA B V 2mW cm to 200mW cm UVC 1mW cm to 100mW cm Spectral Response UVA 320 390nm UVB 280 320nm UVC 250 260nm UVV 395 445nm UV Accuracy Temperature Measurement _ 5 typical 10 maximum Type J Input Range 500 C Maximum Thermocouple range determined by thermocouple wire used 250 C thermocouple wire supplied with unit Sample rate 32 samples per second UV Sample Rates User settable 128 256 512 1024 or 2048 samples per second uv Sample Period Maximum of 1 hour determined by configuration Operating Temperature 0 70 C overtemperature alarm settable from 0 65 C default setting is 65 C Range Ii Unit Operation One Push Button Switch Indicators One Single Tone Audible Indicator Dual Color LED Red Green Battery _ Nickel Metal Hydride NiMH Battery Cycles 500 typical Charging Period 1 hour quick charge at temperatures
4. Frequency Power 60 5 x 18 5 x 42 4 cm 23 8 x 7 3 x 16 7 inches width x height x depth 15 1 kg 33 2 pounds 100 120 or 220 240 VAC 47 to 66 Hz 100 watts maximum 1 000 Environmental Specifications Ambient Temperature Operating Non operating Maximum rate of change Humidity 25 40 C non condensing Altitude Operating Non operating 0 to 40 C 32 to 104 F 40 to 65 C 40 to 149 F 10 C hour 18 F hour 5 to 85 4 600 m 14 950 ft 15 300 m 49 700 ft General Information 1 5 October 22 2000
5. October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 6 4 Background High intensity ultraviolet lamps are commonly used for solventless curing Understanding lamp status during production is critical for maintaining good UV process windows and to minimize out of specification product Monitoring the energy density and irradiance of the lamps can be done at line with various vendor devices At line lamp monitoring devices include but are not limited to conventional flat web UV radiometers from vendors such as International Light and EIT Flat web radiometers must be placed on a web or adhered to it some fashion Consequently the radiometers cannot be run through a nip or through complicated web paths since they would fall off the web or be crushed UV Process Supply UVPS sells an alternative measurement system for complicated web paths The system consists of a thin strip of polyester film with a UV sensitive coating see Figure 1 and a test strip reader see Figure 2 The coating is sensitive to UV A radiation 320 to 380 nm When a test strip is exposed to radiation in this region the optical density decreases The optical density reduction extinction is measured using the test strip reader and correlated to UV A energy density using a calibration chart UV sensitive coating Uncoated end for calibrating Measuring area the TR 202 Tape Reader for strip reader Inserted test strip 0 004 in
6. 99 20964 27 67 088319 99 24306 28 62 954498 98 130379 29 63 027839 95 534464 30 67 732743 98 098744 31 74 639169 99 17281 32 65 450393 96 569903 33 71 064317 99 011391 34 72 596506 94 625888 35 71 907821 97 132421 36 65 523252 94 236834 37 72 373673 99 233046 38 67 282866 95 403145 39 69 276961 98 44478 40 70 211628 95 092485 41 68 241687 99 616392 42 67 295714 89 889073 43 69 381484 76 754789 44 73 375143 92 847122 45 68 929419 93 326514 46 68 926167 Table 3 Variation results for combined lots 160298 amp 310399 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 17 Combining lots increased the unexposed extinction error by 2 5 to 4 times as measured by the spectrophotometer Measurements that are more accurate can be attained by simply using test strips from the same lot for calibration and for evaluating the process UV bulbs 7 B Fusion F600 D Bulb 7 B i Data The F600 D bulb was evaluated by two operators on two different dates using the EIT UV PowerMAP The data is depicted below in Chart 2 Fusion F600 D Bulb Calibration Curve for EIT UV A Energy Density vs Extinction Decrement Data taken with EIT UV PowerMAP amp UV Process Supply Rad Check 01 Test Strips E 2 i gt N i v a gt 3 5 o i wi gt 5 E rrj 0 4 0 5 0 6 Extinction Decrement U E U Units Linear Regression Model Error
7. A UV B 230 240 250 260 270 375 400 425 450 Wavelength nm Wavelength nm UV C UV V Figure 22 Spectral response curves Optics Locations The locations of the optics for each UV channel are shown in Figure 23 The UV PowerMAP has all four channels the UV MAP Plus has only one channel Optics Head Figure 23 UV channel locations 100200 PWR Rev A 11 98 31 October 22 2000 Page 29 Calibration and Analysis of Ultraviolet Radiochromic Strips Technical Data for UV Power Puck Appendix B This appendix contains technical data regarding the EIT Inc UV Power Puck radiometer SOURCE EIT Inc 1994 UVICURE Plus amp UV Power Puck User s Manual Sterling VA Author adou joy WM auey o Palqns suoyeRsypeds AXHXM Wu 9 607 X POLL X B HOE SIUL CZ 8 X Lb X TL suorsuau q aseD SurAueD Ssure13 g p punod 34313 M aseD Zure J9A0D 1034X UOJ U yuesisas jjn g JoJOWOIPeI a epOUTULODIe 0 10u aUeYeINAJOd mI Ene aseD BurAuey P S ssayureys uNUTUINTy Hene Beed sures EEE S2OUNO GZ LI 34313M H X q sayaw L Z X LLL SOYU OG X 09 F suorsuawq asn yeordAy y m sSurpeas OOST cajry Gpeg yuayeatnba 10 OSEZUD OAues OsHT1q aoeING Sp wni afqeaoeydas sasn Om sapped n Aay ou apow AyTdSIA sanunu z paasasqo 31 u OU apow NNA SANU p ponaq yno auT j Papioa st jueLrem y sry Spaaoxe aunjesadwia pewiaqut JI D 008 S aanjesaduray pe
8. Supply model VPS 6 Provided power to Fusion lamps Dial control for power settings ranging from 25 to 100 in 5 increments 4 Cincinnati Fan amp Ventilation Co Inc fan model PB 144 with a Baldor High Efficiency Electric Motor model M3613T Single speed blower which supplied ambient air to cool the lamps 5 B Line Speed Control 1 Durant Digital Instruments Shaft Encoder model 39700 060 60 pulses rev with October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 11 Dynapar Corporation Measuring Wheel model 83 12X 5 Mounted on an idler roll to measure line speed and provide signal to a digital display 2 Red Lion Controls 6 Digit Apollo Time Base Rate Indicator model APLR Displayed line speed in feet per minute 3 Dayton Electric Manufacturing Company SCR Controller model number not available Controller has dials for adjusting torque and line speed signals sent to gearmotor 4 Dayton Electric Manufacturing Company Permanent Magnet DC Gearmotor model 4Z136A Used to rotate a shaft with a 7 in diameter core which moved the Miltec conveyor belt through the cure chamber 5 C Energy Density Measurement 1 EIT Inc UV Radiometer model UV PowerMAP High power 200 mW cm to 20 W cm UV radiometer used to measure UV A energy density from 320 to 390 nm on the F600 D and H bulb The UV PowerMAP is a UV irradiance data logger which downloads energy density and irradiance values t
9. The Background section describes the use of UV curing and why monitoring lamp output is important for process and product understanding This section also describes the Rad Check system its advantages versus conventional radiometers and how test strips can be calibrated for energy density measurements The Equipment section is a summarized breakdown of the instruments and equipment used to perform the calibration and validation experiments The next section Experimental Procedure describes how the calibration charts were generated and validated how to store and handle the test strips and how to calibrate the test strip reader and take extinction measurements The Results section first explores the lot to lot test strip variation Then calibration charts for the Fusion F600 D bulb and F600 H bulb are presented which depict the experimental data The Results section also discusses performance limitations calibration validation error analysis and confidence bands how to use the calibration charts important considerations for using the test strips and charts and a short evaluation of two different radiometers The Conclusions section highlights important points from each of the previous sections The next section Suggestions for Future Work describes appropriate research for a complete analysis of the Rad Check system Finally the Appendices section contains detailed specifications for the instruments and equipment used in the experiments
10. Values Linear Regression Model Based on Op 1 Data EIT UV A Energy Density mJ cm 628 87 Dec 0 04 Upper 95 Conf Band Dec UV A Energy Density R 0 9984 6 Lower 95 Conf Band e Op 1 Data 8 17 99 Lot 160298 A Op 2 Data 12 17 99 Lot 310399 Chart 2 Test strip extinction decrement data and model for Fusion F600 D bulb The centerline in Chart 2 is the linear regression model based on Operator 1 s data taken on 8 17 1999 The model does not consider data beyond DEC 0 80 because of non linearity beyond that point Operator 2 s data taken on 12 17 1999 was an attempt to validate the model Operator 1 used test strips from lot 160298 Operator 2 used test strips from lot 310399 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 18 7 B ii Performance Limitations After the extinction decrement reaches 0 80 the test strips indicate a non linear response to increasing energy density levels The non linear response is probably due to saturation of the coating At energy density levels higher than 500 mJ em UV A on the Fusion D bulb the coating started to blister UVPS reports the maximum value of 300 mJ cm However the response of the test strip to energy density is clearly linear up to DEC 0 80 and 500 mJ cm UV A energy density 7 B iii Validation Operator 2 s data falls mostly within the confidence bands but the overall trend is lower th
11. are combined Test strips from two lots were examined using an HP 8452A UV Vis spectrophotometer which revealed excessive variability for both the exposed and unexposed extinction values Since energy density predictions rely on accurate extinction decrements improved energy density predictions can be obtained by simply using test strips from the same lot for generating the calibration chart and for process measurements The relationship of energy density to extinction decrement is linear up to DEC 0 80 after which the test strips display a non linear response to increasing energy density levels It is suspected that the test strips saturate when the extinction decrement reaches this level UVPS states the maximum UV A energy density for the Rad Check 01 test strips as 300 mJ cm However Chart 2 suggests an actual maximum of 500 mJ cm for the F600 D bulb Chart 3 suggests an actual maximum ranging from 200 to 275 mJ cm for the F600 H bulb depending on the test strip lot If multiple bulbs are to be measured the test strips could easily saturate Therefore multiple bulbs should be examined individually Charts 2 and 3 also show that the linear regression models do not hold for out of lot test strips Calibration charts should be generated using test strips from the same lot For the models October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 25 to be valid for in lot test strips used to evaluate pro
12. below 35 C Charging Adapter AC input 100 130VAC 50 60Hz or 200 240VAC 50 60Hz __ DC output 12 VDC 250 mA Operating Time Determined by configuration Guideline four channels on 512 Samples second for a 2 minute sample period yields 30 readings on one charge Communication to PC PowerView Software Format RS232 Serial Port mg Speed User settable 9600 19200 38400 57600 or 115200 baud Minimum Computer Requirements Interface Mechanical Specifications or Windows 98 operating system Pentium 60MHz 16MB RAM one serial port one parallel port 20MB space available on hard drive CD ROM drive or 3 5 HD floppy disc drive Windows 95 Windows based fully graphical interface Unit Dimensions 1 3 50 W X 9 0 L X 0 5 D 8 89cm X 22 86cm X 1 27cm Weight Materials 20 2 ounces 570 grams Aluminum chassis with stainless steel covers Specifications are subject to change 100200 PWR Rev A 11 98 Table 2 Electrical and mechanical specifications 30 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 28 Spectral Response Curves The Spectral Response Curves for the four UV channels are shown in Figure 22 below The UV PowerMAP has all four channels the UV MAP Plus has only one channel A 300 325 350 375 400 425 250 275 300 325 350 375 Wavelength nm Wavelength nm UV
13. polyester film base Double sided tape Figure 1 Diagram of Rad Check test strip Figure 2 TR 202 test strip reader October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 7 At the time of this report UVPS sells three types of test strips that can measure different levels of UV A energy density see List 1 below e Rad Check 01 e Rad Check 01 D e Rad Check 01 L List 1 Test strips available from UV Process Supply Inc Rad Check 01 test strips are sensitive to energy density levels ranging from 0 to 300 mJ cm If higher levels are present Rad Check 01 D strips can measure beyond 300 mJ cm For low radiation processes the Rad Check 01 L strips have improved accuracy with a sensitivity range of 0 to 200 mJ cm The advantage of the test strips is that lamps can be characterized for UV A energy density in processes unsuitable for conventional radiometers This means test strip calibration is usually performed on a separate flat web lamp system To provide exact energy density values for exposed test strips the calibration lamp system should be as similar as possible to the lamp system in the process i e same bulb type same manufacturer similar lamp focus same reflector type cleanliness etc It is important to realize that different UV bulb types have different spectral outputs For example a specific test strip extinction value will correspond to a different UV A ene
14. A energy density for the test strips on the Fusion H bulb was 200 to 275 mJ em depending on the test strip lot In comparison UVPS states the maximum energy density value of 300 mJ cm for the Rad Check 01 test strips 7 C iti_ Validation Operator 1 s data does not fall within the confidence bands of the model However Operator 2 s data taken on 5 11 2000 follows the centerline closely validating the model for in lot test strips Again the overall linear trend is verified but the model does not hold for test strips from the different lot Since the model does not hold for test strips for the different lot this suggests that a calibration chart should be generated for each lot To evaluate the process UV bulbs the test strips must belong to the same lot used to generate the calibration chart 7 C iv_Error Analysis amp Confidence Bands Instrument and random error was calculated for the UV PowerMAP and UV Power Puck using RSS and the Student t test with a 95 confidence level The typical error was 7 and 10 respectively of the measured UV A energy density The extinction decrement error was calculated using RSS with partial differentials and the Student t test The typical error was 0 03 in arbitrary units The reported errors for the UV PowerMAP and UV Power Puck and test strips are independent of the energy density exposure up to DEC 0 80 The upper and lower 95 confidence bands were generated us
15. Calibration amp Analysis of Ultraviolet Radiochromic Strips Report By Aguirre F M Funches T C Kuhns D W Report Date October 22 2000 Edited 2004 01 30 by Frank M Aguirre Calibration and Analysis of Ultraviolet Radiochromic Strips Page 2 1 Abstract High intensity ultraviolet UV lamps are commonly used for solventless curing Understanding lamp status during production is critical for maintaining UV process windows and to minimize out of specification product Monitoring the energy density and lamp irradiance can be done at line with various vendor devices However flat web radiometers cannot pass through a nip or through complicated web paths since they would fall off the web or be crushed As an alternative UV Process Supply sells the Rad Check system for checking UV A energy density in such processes The system consists of a thin polyester strip with a UV sensitive coating and a reader The optical density of the coating decreases under UV A exposure This decrease extinction decrement is measured using the reader and can be correlated to energy density measurements via radiometer calibration This report examines the Rad Check 01 test strips for error variability and sensitivity on the Fusion UV Systems F600 D bulb and H bulb Calibration charts were generated for the strips and show linearity of energy density to extinction decrement up to 500 and 250 mJ cm EIT UV A for each bulb respectively Error analys
16. D bulb the band width was approximately 30 mJ cm at low extinction decrement and approximately 50 mJ cm at high extinction decrement see Chart 2 In comparison the band width for the Fusion H bulb was approximately 10 mJ cm at low extinction decrement and approximately 25 mJ cm at high extinction decrement see Chart 3 If product properties were negligibly sensitive to the magnitude of the energy density range then the test strips would be useful for determining and maintaining a UV A energy density process window If tighter process control were needed then the Rad Check 01 test strips would not be sufficient Second the test strips appear to saturate when DEC is approximately 0 80 If more than one lamp is being studied the test strips could easily saturate if the maximum total energy density is exceeded For the F600 D bulb the maximum energy density that corresponds to DEC 0 80 is approximately 500 mJ cm7 whereas the maximum energy density corresponding to an F600 H bulb ranges from 200 to 275 mJ em depending on the test strip lot If October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 22 saturation is possible multiple lamps should be studied individually Third it may not be physically possible to adhere multiple test strips to a moving web if the line speed is too fast By measuring lamps at the power setting used for the process with a slower line speed the true pro
17. F600 H Bulb 7 C i Data 19 7 C ii Performance Limitations 20 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips 8 Conclusions 9 Suggestions for Future Work Appendices Page 4 7 C iii Validation 20 7 C iv Error Analysis amp Confidence Bands 20 7 D Using the Calibration Charts 21 7 E Important Considerations 2I 7 F UV PowerMAP vs UV Power Puck 22 23 26 A Technical Data for UV PowerMAP 27 B Technical Data for UV Power Puck 29 C Technical Data for Test Strips amp Reader 31 D Technical Data for HP Spectrophotometer 33 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 5 2 Objective To evaluate UV Process Supply Inc CON TROL CURE Rad Check 01 UV energy density test strips with regards to error variability and sensitivity To calibrate the strips using ultraviolet radiometers from EIT the UV PowerMAP and UV Power Puck To provide EIT UV A energy density calibration charts for Fusion UV Systems F600 D bulb and H bulb 3 Introduction This report summarizes the error variability and sensitivity of UV Process Supply CON TROL CURE Rad Check 01 UV energy density test strips The report is divided into seven major sections which describe the Rad Check system and calibration equipment experimental procedure results conclusions suggestions for future work and relevant appendices
18. Inserted into cure chamber this direction Approximate location of UV A filter see Appendix B Figure 4 Positioning of Rad Check 01 test strip on EIT UV Power Puck radiometer The UV A energy density measurement is plotted versus the extinction value to create a calibration data point Lamp power and line speed determines the amount of radiation seen by both the radiometer and the test strip By varying the lamp power and line speed a scatterplot calibration chart of UV A energy density versus extinction is created Thickness and chemical composition variability of the UV sensitive coating results in October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 9 exposed and unexposed extinction variability To account for strip to strip variability we can use the concept of extinction decrement Extinction decrement is simply the normalized extinction decrease of an exposed test strip Extinction decrement is hereby defined as the unexposed extinction minus the exposed extinction divided by the unexposed extinction In the form of an equation U E DEC EQ 1 7 Q where DEC is extinction decrement U is the unexposed extinction and E is the exposed extinction Equation 1 can be simplified to DEC 1 EQ2 In addition to normalization UVPS recommends at least three strips be exposed and averaged to reduce measurement error More specifically a single test strip should be adhered to th
19. an the model The cause of the lower trend is unknown but the only difference between the Operator 1 and 2 s data is the test strip lot The different slope suggests lot 310399 had a different response to the UV A energy density Therefore a calibration chart should be generated for each lot and test strips from that same lot should be used for energy density measurements on the process UV bulb 7 B iv_Error Analysis amp Confidence Bands Instrument and random error was calculated for the UV PowerMAP using RSS and the Student t test with a 95 confidence level The typical error was 6 of the measured UV A energy density The extinction decrement error was calculated using RSS with partial differentials and the Student t test The typical error was 0 04 in arbitrary units The reported errors for the UV PowerMAP and test strips are independent of the energy density exposure up to DEC 0 80 The upper and lower 95 confidence bands were generated using the worst case error scenarios for the UV PowerMAP and extinction decrement The upper band was generated using 6 energy density with 0 04 DEC The lower band was generated using 6 energy density with 0 04 DEC The concept of the bands is that we are 95 confident that the true process energy density lies within the upper and lower limits for a predicted energy density value obtained using an averaged extinction decrement The bands assume that the test strips are from t
20. cess UV bulbs the average extinction decrement should be calculated using the same sample size as that used for the calibration chart Error analysis for the extinction decrement used RSS in conjunction with partial differentials and the Student t distribution using a 95 confidence level Error analysis for energy density measurement used RSS in conjunction with the Student t distribution using a 95 confidence level Outliers were eliminated using Thompson s Tau Rejection Criteria The error values for each bulb are summarized in Table 4 below Radiometer AEnergy Density Bulb for Calibration ADEC AU mJ cm eir UV A EIT UV i Fusion F600 D Bulb S werMApw 0 04 7 Fusion Feo0H Buib El U Power 0 03 10 Puck Table 4 Summary of error analysis for extinction decrement and UV A energy density The maximum and minimum error values were used to create the 95 confidence bands for the linear regression models The models themselves predict the true process energy densities The confidence bands provide the predicted ranges for true energy densities with 95 confidence i e the 95 probability that the true value lies within the upper and lower limits for a predicted energy density The energy density range using the 95 confidence band might be too large to determine a UV process window This is because properties of the product could change significantly within the magnitude of the range For the D bulb th
21. cess energy density can be estimated using the relation that twice the line speed is equal to half the energy density In form of an equation Measurement Line Speed True Process Energy Density Measured Energy Density x EQ3 Process Line Speed where Measured Energy Density is obtained from the extinction decrement calibration chart Measurement Line Speed is the line speed at which the test strips were run under the process lamp usually slower or faster than the normal process line speed and Process Line Speed is the line speed at which the process is normally run The width of the energy density range can be estimated using the same equation Finally test strips may saturate if the measurement line speed is too slow If this is the case measurements should be taken at a faster line speed such that the strips do not saturate and then adjust for the process line speed using Equation 3 the lamp would remain at the power setting normally used for the process This method is useful if the process has high energy density at slow line speeds 7 F UV PowerMAP vs UV Power Puck Since the calibration charts depend upon radiometer measurements the effects of using the EIT UV PowerMAP versus the UV Power Puck were not known A study was done to explore these effects if any A single lot was used for the experiments lot 160298 on the Fusion H bulb The results are shown below in Chart 4 October 22 2000 Calibration an
22. d Analysis of Ultraviolet Radiochromic Strips Page 23 Fusion F600 H Bulb Calibration Curve for EIT UV A Energy Density as a Function of Extinction Decrement Combined Data from EIT UV Power Puck amp PowerMAP DA Q w a Oo wo Q N a Oo N Q ai a F 2 3 E gt N c o a gt a fo w q gt 5 E wi e Q a Oo 0 4 0 5 0 6 Extinction Decrement U E U Units Linear Model Based on Power Puck Data Linear Regression Model Error Values Upper 95 Conf Band EIT UV A Energy Density mJ cm arene Lower 95 Conf Band oe Dec Dohsi 4 ren e Power Puck Data Lot 160298 R 0 9896 m PowerMAP Data Lot 160298 Chart 4 Comparison of UV PowerMAP and UV Power Puck for producing a calibration chart for the Fusion F600 H bulb The data obtained in Chart 4 does not indicate a significant variance in energy density measurements for generating a calibration chart using either radiometer 8 Conclusions UVPS sells a measurement system for checking UV A energy density in processes that have complicated web paths through which a conventional radiometer cannot pass The system consists of a thin strip of polyester film with a UV sensitive coating and a test strip reader When a test strip is exposed to UV A the optical density of the coating is reduced This reduction is measured as extinction by the test str
23. de max rel sensitivity 320nm 50 rel sensitivity 300 360nm LL UV Process Supply Inc 773 248 0099 800 621 1296 888 UVLAMPS 1229 W Cortland St FAX 773 880 6647 800 99FAXUV Chicago IL 60614 4805 UV FAXTS Service 773 880 6649 Page 32 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 33 Appendix D Technical Data for HP Spectrophotometer This appendix contains technical data regarding the HP 8452A Diode Array Spectrophotometer SOURCE Hewlett Packard Company 1990 HP 8452A Diode Array Spectrophotometer Handbook Federal Republic of Germany Author Performance Specifications Item UV VIS UV Extended Visible Instrument Instrument Instrument Full Spectrum Scan 0 ls 0 1 s 0 1 s Time Until Next Scan Up to 35 wavelengths 0 1s 0 1s 0 1s no variance 0 1 s integration Full spectrum scan 0 6 s 0 6 s 0 6 s no variance 0 1 s integration Full spectrum scan 1 8 s 1 858 1 88 with variance 0 5 s integration Time To Display Full Spectrum 6s 6s 6s HP 9000 Series 300 amp MS DOS UV VIS software Wavelength Range 190 820 nm 190 510 nm 470 1100 nm Wavelength Accuracy 2 nm 1 nm 2 nm 190 400 nm Wavelength Reproducibility 0 05 nm 0 05 0 05 nm typical with constant conditions Spectral Bandwidth 2 nm lnm 2 nm 190 400 nm Photometric Range 0 5 s measurements at 350 nm 0 0022 3 3 AU 0 0022 3 3 AU Full dynamic range dA A 50 0 5 s measureme
24. e band width was approximately 30 mJ cm at low extinction decrement and approximately 50 mJ cm at high extinction decrement In comparison the band width for the Fusion H bulb was approximately 10 mJ cm at low extinction decrement and approximately 25 mJ cm at high extinction decrement If product properties were negligibly sensitive to the magnitude of the energy density range then the test strips would be useful for determining and maintaining a UV A energy density process window If tighter process control were needed then the Rad Check 01 test strips would not be sufficient October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 26 9 Suggestions for Future Work At the time of this report UVPS sells three types of Rad Check test strips for measuring different levels of UV A energy density Rad Check 01 test strips 0 300 mJ cm were evaluated for this report To complete the test strip analysis the Rad Check 01 D and 01 L test strips should be evaluated The effect of multiple bulbs on the test strips was not studied for this report Operator to operator variability the procedure used to expose and measure the test strips was not quantified for this report October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Appendix A Technical Data for UV PowerMAP This appendix contains technical data regarding the EIT Inc UV PowerMAP radiometer
25. e dirt and oil deposits on the areas read by the strip reader approximately 11 mm from each end of the strip 6 D Calibrating the TR 202 Test Strip Reader Once test strips were received from UVPS they were refrigerated 40 50 F Calibration of the strip reader was done in an area that had filters that blocked UV radiation from the fluorescent lamps When the strip reader is first turned on it must be calibrated to account for inherent optical density and thickness variation of the polyester base film Calibration is performed by inserting the uncoated end of the test strip into the reader and pressing Cal The zero point is stored in the memory of the instrument UVPS states that the zero point is valid for about ten extinction measurements after which the reader should be re calibrated using the next test strip The coated side of the strip can face either up or down for calibration 6 E Measuring the Unexposed Extinction After calibration the message TR 202 Ready to measure is displayed on the LCD screen The coated end of each strip was inserted into the reader to measure the unexposed extinction U The measurements were performed in the same area where the strip reader was October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 14 calibrated After the U extinction was measured each sample set of five was placed in an envelope and refrigerated until they were run through the cure chamber the fo
26. e for the combined lots and as separate lots Tables 1 2 and 3 show the results of the calculations UV Process Dose Tape Lot 160298 001 UV Process Dose Tape Lot 310399 001 Forn 5 Unexposed Relative U Absorbance U AU Avg U 1 sy AU Error Forn 5 Unexposed Relative U Strip Absorbance U AU Avg U 1 sy AU Error 98 369679 95 21570687 5 89 T 8 99 692723 80 325976 99 20964 99 24306 98 130379 95 534464 98 098744 99 17281 96 569903 99 011391 94 625888 97 132421 94 236834 99 233046 95 403145 98 44478 95 092485 99 616392 89 889073 76 754789 92 847122 93 326514 70 215624 69 04951104 3 04 6 4 5 70 106595 70 536936 67 088319 62 954498 63 027839 67 732743 74 639169 65 450393 71 064317 72 596506 71 907821 65 523252 72 373673 67 282866 69 276961 70 211628 68 241687 67 295714 69 381484 73 375143 68 929419 68 926167 00 NI olas ojn Table 1 Variation results for lot 160298 Combined UV Process Dose Tape Lots 310399 001 amp 160298 001 Lot 310xxx Unexposed Lot 160xxx Unexposed Strips Absorbance U AU Strips Absorbance U AU AvgU 1 gy 2 oy 3 oy AU Error 98 369679 24 70 215624 82 132609 13 86 27 72 41 59 17 99 692723 25 70 106595 80 325976 26 70 536936
27. e radiometer and passed under the calibration lamp Thus each strip has its own corresponding energy density value Averaging the energy density measurements and corresponding extinction decrements helps minimize random error Coupling averaged extinction decrements with averaged energy density measurements creates a linear calibration chart of EIT UV A energy density as a function of DEC 5 Equipment 5 A Cure Chamber amp Lamp System See Figure 5 1 Fusion UV Systems Corporation UV Cure Chamber model DRW 120QNH Cure chamber through which EIT radiometers and Rad Check test strips were passed A Miltec 12 in wide UV resistant conveyor belt carried the radiometers and test strips through the chamber October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 10 High intensity Nitrogen purge Fusion F600 lamp systems 600 W in Adjustable lamp height Air knife Digital tachometer Continuous UV resistant conveyor belt ap e A hs Ben al i Variable speed controller amp motor Single speed air blower Figure 5 Fusion Systems UV cure chamber 2 Fusion UV Systems Corporation Irradiator model EPIQ 6000 Irradiated via microwaves a single 10 in wide F600 600 W in electrodeless UV bulb housed within the unit Standard aluminum reflectors used A Fusion D bulb mercury doped with iron and Fusion H bulb mercury were examined for this report 3 Fusion Systems Corporation Variable Power
28. enerating a Calibration Chart To generate a calibration chart a sufficient number of test strips required exposure to different levels of UV A energy density The different UV A energy density levels were attained by varying the VPS 6 power supply and the line speed controller A total of 100 test strips in sample sets of five were used to generate a calibration chart Power was set to 40 60 80 and 100 At each power level line speed was set to 70 80 90 100 and 110 ft min Five test strips were run at each line speed for a specific power setting When five strips were exposed the line speed was increased to the next setting After test strips were run at 110 ft min the power was increased to the next setting and the line speed was reset to 70 ft min All 100 test strips were run under the same point of the lamp approximately 2 in from the operator side of the lamp The lamp was allowed to stabilize for 10 minutes on start up and when lamp power was changed The lamp was 0 5 in out of focus for all the experiments 6 B Validating a Calibration Chart A total of 60 test strips in sample sets of five were used to validate a calibration chart Power was set to 60 40 100 and 80 At each power level line speed was set to 110 70 and 90 ft min Five test strips were run at each line speed for a specific power setting When five strips were exposed the line speed was increased or decreased to the next setting After test strips were r
29. h a density of 1 73 Adjust the K factor to 0 95 to obtain a recalibrated optical density of 1 62 This will hold the values within acceptable error limits 3 Reproducibility and Measuring Accuracy When establishing System repeatability we determined mean values double standard deviation and error percentage The error percentage is approximately 2 for test strips not exposed to radiation This increases slightly following exposure and varies slightly depending on dose strength To obtain a reliable result perform at least three measuring sequences for each determination This method minimizes possible deviations and permits clear determination of the correct value Direct comparison between exposed and non exposed test strips is favorable for a more accurate evaluation of radiation tests Exposed and non exposed tapes are measured one after the other and the quotient ElEx is formed This method recognizes and minimizes errors relating to layer thickness The calibration curves provided with each test strip batch indicate the dependence of the extinction E as well as the dependence of the quotient E Eo Test Strip Specifications Dose Levels Test Strip 01 0 300 mJ cm2 Range 320 380nm Durability Approx 6 months Storage Store in dark cool environment preferably refrigerated at 4 10 C Packaging Quantities of 100 Dosimeter Specifications Light source 12V 6w commercial halogen lamp Sensor UV selective photodio
30. he same lot and that the sample size used to measure a process bulb is equal to the sample size used to generate the calibration chart For October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 19 the experiments described in this report the sample size was five If an operator were to use a smaller sample size for measuring the process UV bulbs then random error would likely increase for both energy density and extinction decrement Consequently the increased error will expand the confidence bands If a larger sample set were used the random error would likely reduce the random error and tighten the confidence bands For example if an operator evaluates the process UV bulbs using three strips and calculates the average extinction decrement he or she would need to consult a calibration chart generated from sample sets of three Similarly if an operator evaluates the process UV bulbs using ten strips and calculates the average extinction decrement he or she would need to consult a calibration chart generated from sample sets of ten 7 C Fusion F600 H Bulb 7 C i_ Data The F600 H bulb was evaluated by two operators on three different dates using the UV PowerMAP and UV Power Puck The data is depicted below in Chart 3 Fusion F600 H Bulb Calibration Curve for EIT UV A Energy Density vs Extinction Decrement Data taken with EIT UV PowerMAP UV Power Puck amp UV Process Supply Rad Check 01 Test Strips
31. ing the worst case error scenarios for the UV PowerMAP and extinction decrement The upper band was generated October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 21 using 7 energy density with 0 03 DEC The lower band was generated using 7 energy density with 0 03 DEC 7 D Using the Calibration Charts To use the model depicted in Chart 2 or 3 the user would expose five test strips under the same point of a process bulb calculate the average extinction decrement and record the predicted energy density value and range from the chart The model only provides the predicted value for the true energy density in the process The confidence band provides the predicted range for the true energy density with 95 confidence For example suppose the average DEC for five test strips was 0 50 Using Chart 2 the predicted process energy density would be 315 45 mJ cm UV A with 95 confidence In other words we would be 95 confident that the true process energy density is within 45 mJ cm of 315 mJ cm 7 E Important Considerations First the most significant consideration when using the Rad Check 01 test strips is the width of the confidence band The width of the band i e the range for a predicted energy density might be too large for determining the process window for a product This is because properties of the product may change significantly within the magnitude of the range For the
32. ip reader To provide actual energy density October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 24 measurements using the test strips calibration is required on a separate flat web UV system that has a similar configuration lamp type focus distance power supply etc as the actual process system By using a UV radiometer in conjunction with UVPS Rad Check 01 test strips calibration charts can be generated for UV A energy density as a function of extinction decrement Proper storage and handling of the test strips are necessary for obtaining reliable extinction measurements The test strips available in airtight packets of 50 should be stored in a refrigerator between 40 and 50 F Limited transportation at room temperature does not affect the coating When handling the strips lint free gloves such as latex or Nitrile should be worn In addition the test strips should not be exposed to stray UV light from fluorescent or mercury lamps Exposure to sunlight should be avoided UVPS recommends that when a strip is removed from is packet it should be exposed to UV as soon as possible However the unexposed extinction U appears stable for at least a few weeks after a strip is removed from its packet measured returned to its packet and placed back into refrigeration The exposed extinction E appears stable at room temperature Lot to lot strip variation significantly increases the decrement error if lots
33. is 95 confidence was used to generate confidence bands on the calibration charts The bands provide confidence ranges for predicted process energy density The energy density confidence range was approximately 40 mJ cm and 20 mJ cm on the Fusion D bulb and H bulb respectively If product properties were insensitive to the magnitude of the energy density range then the test strips would be useful for determining and maintaining a UV A energy density process window October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 3 Table of Contents Title Page 1 1 Abstract 2 2 Objective 5 3 Introduction 5 4 Background 6 5 Equipment 5 4 Cure Chamber amp Lamp System 9 5 B Line Speed Control 10 5 C Energy Density Measurement 11 5 D CON TROL CURE Rad Check UV Measurement System 11 5 E HP Spectrophotometer 12 6 Experimental Procedure 6 A Generating a Calibration Chart 12 6 B Validating a Calibration Chart 12 6 C Test Strip Storage amp Handling 13 6 D Calibrating the TR 202 Test Strip Reader 13 6 E Measuring the Unexposed Extinction 13 6 F Adhering the Test Strip to the Radiometer 14 6 G Measuring amp Evaluating the Exposed Test Strip 14 7 Results 7 A Test Strip Variation 14 7 B Fusion F600 D Bulb 7 B i Data 17 7 B ii Performance Limitations 18 7 B iii Validation 18 7 B iv Error Analysis amp Confidence Bands 18 7 C Fusion
34. llowing day The coated side of the strip can face either up or down in the strip reader when measuring the U extinction However it is recommended to follow the same measurement procedure to minimize operator to operator variability For the experiments described in this report the coated side of each test strip faced up 6 F Adhering the Test Strip to the Radiometer Using the double sided tape on the test strip a single strip was adhered to the radiometer so that the coated side faced the lamp Since each test strip possesses a small degree of curl a second piece double sided tape was used to keep the strip flat when run under the lamp see Figures 3 and 4 The coated side of the test strip must face the UV source 6 G Measuring amp Evaluating the Exposed Test Strip After a strip was exposed to the UV lamp the coated end of the strip was placed into the strip reader and the exposed extinction E was measured and recorded This was done in an area that had filters that blocked the UV from the fluorescent lamps The extinction decrement DEC was calculated for each test strip The corresponding UV A energy density from the UV radiometer was also recorded The extinction decrements and energy density measurements were averaged for each sample set of five The standard deviation was also calculated for error analysis which is discussed in a later section of this report Line speed power setting extinction measurements and energy densit
35. n which does not affect the optical densities of the test strips Chart 1 below shows typical UV A absorbance curves for test strips from both lots Fusion F600 D Bulb Exposed Dataifor 60 Power 90 gt Typical Absorbance Curves for UVPS Rad Check 01 UV Test Strips ft min gt 210 mJ cm i P i aa oe ae Data taken with HP 8452A UV Vis Spectrophotometer Ey lt o o S 2 i a 2 lt 350 Wavelength nm Unexposed Lot 160298 001 s Exposed Lot 160298 001 Unexposed Lot 310399 001 A Exposed Lot 310399 001 Chart 1 Typical absorbance curves for Rad Check 01 test strips from two separate lots October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 16 It is evident from Chart 1 that test strips from differing lots do not have the same sensitivity to UV A The extinction variance was further explored for the unexposed absorbance The unexposed absorbance intensities were integrated from 320 to 390 nm for the 23 test strips from each lot The average standard deviation and error were calculated for the integrated intensities Twenty three test strips were used to determine the lot average and standard deviation to minimize bias from a small sample size A theoretical sample size of five was used to calculate random error using the Student t distribution with 95 confidence Calculations were don
36. nts at 600 nm 0 0011 2 8 AU Photometric Accuracy at 1 AU with NBS 930D 0 005 AU 0 005 AU solid filter at 440 nm with NBS 930D 0 005 AU solid filter at 635 nm Baseline Flatness 0 5 s blank followed by 0 5 s measurement lt 0 001 AU rms lt 0 001 AU rms 0 0005 AU rms General Information 1 3 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 34 Performance Specifications continued Item UV VIS UV Extended Visible Instrument Instrument Instrument Noise Y0 AU 60 x 0 5 s measurements lt 0 0002 AU rms lt 0 0002AU rms lt 0 0001 AU rms 500 nm 340 nm 780 nm Stability 0 AU constant ambient conditions Measured over 1 hour every 5 s without internal referencing lt 0 002 AU lt 0 002 AU lt 0 001 AU 340 nm 340 nm 620 nm with internal referencing at 400 lt 0 001 AU lt 0 001 AU nm Measured over 60 s period every lt 0 001 AU lt 0 001 AU 5s Stray Light measured with Hoya 056 at 220 lt 0 05 lt 0 05 nm and 340 nm measured with Schott RG850 lt 0 05 filter at 530 nm and 650 nm All specifications are measured after one hour from cold start or from lamp turn on with no cell or filter unless specified 1 4 General Information October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 35 i Physical Specifications Dimensions Weight Line Voltage selectable
37. o a PC via a serial connection Sample rate of 512 samples sec selected with threshold OFF See Appendix A for detailed specifications 2 EIT Inc UV Radiometer model UV Power Puck UV radiometer 5 mW cm to 5 W cm used to measure UV A energy density from 320 to 390 nm on the F600 H bulb The UV Power Puck measures and displays the total energy density and peak irradiance seen by the detector The data is displayed on 4 digit LCD screen on the radiometer See Appendix B for detailed specifications 5 D CON TROL CURE Rad Check UV Measurement System 1 Radiochromic UV energy density strips Rad Check type 01 Test strips adhered to the EIT radiometers and passed underneath calibration lamps Exposure to UV A radiation reduces the optical density extinction of the UV sensitive coating which is measured using the TR 202 test strip reader See Appendix C for detailed specifications 2 Extinction measurement instrument model Tape Reader TR 202 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 12 Used to measure the test strip extinction values See Appendix C for detailed specifications 5 E HP Spectrophotometer 1 Hewlett Packard UV Vis Diode Array Spectrophotometer model HP 8452A This instrument was used to evaluate the lot to lot UV A absorbance variability for exposed and unexposed test strips See Appendix D for detailed specifications 6 Experimental Procedure 6 A G
38. rgy density on a Fusion F600 D bulb versus a Fusion F600 H bulb Therefore a calibration chart is needed for each bulb type To correlate extinction with an energy density measurement a radiometer is passed under the lamp of the calibration system at the same time as a test strip This is best accomplished by adhering the strip to the radiometer so that the measuring spot of the strip reader 11 mm from the coated end of the test strip aligns with the UV A filter in the radiometer Positioning the test strip in this manner ensures the radiation incident on the detector in the radiometer will be the same radiation incident on the test strip see Figure 3 for positioning the test strip onto the EIT UV PowerMAP A second piece of double sided tape helps secure the loose end of the strip to the radiometer The test strip is positioned similarly for the EIT UV Power Puck which has the same UV filter configuration see Figure 4 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 8 9 0 in Second piece of double sided tape Inserted into cure Approximate location Coated end of test strip B of UV A filter see Measuring spot for reader 11 chamber this direction Appendix A mm from strip end Figure 3 Positioning of Rad Check 01 test strip on EIT UV PowerMAP radiometer Second piece of double sided tape Coated end of test strip Measuring spot for reader 11 mm from strip end
39. un at 90 ft min the power was set to the next level and the line speed was reset to 110 ft min Each sample set was placed randomly cross web on the belt such that all test strips in a sample set were run under the same point of the lamp Again the lamp was allowed to October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 13 stabilize for 10 minutes at start up and after changing the power setting 6 C Test Strip Storage amp Handling Storage and handling of the test strips are important for obtaining accurate extinction measurements Since the coating on the polyester film is UV sensitive test strips should not be exposed to sunlight mercury lamps or fluorescent lamps The coating also has a certain amount of thermal sensitivity so the strips should be stored in a refrigerator between 40 and 50 F 4 10 C Limited transportation at room temperature is okay The strips are available from UVPS in packets of 50 which are airtight and protect the strips from UV exposure UVPS recommends exposing a test strip to UV radiation as soon as possible after removing it from its packet However the unexposed extinction U appears stable for at least a few weeks after a strip is removed from its packet measured returned to its packet and placed back into refrigeration The exposed extinction also appears stable It is recommended to handle the strips using lint free gloves such as Nitrile or latex This will minimiz
40. usajur WMUNXeUT ey NOLL VD y3 00 st aanjezaduray uayM sayedtpul uere arqrpne spouiad yz0ys 105 sain eradwia ewsa xa JaySry yonu sayesajo ounyesadwa euzu gt o GL 0 sa8uey amjyeradwiay Buyerado auso Ajayewrxoiddy rasuodsay jeneds WUNGE NZE VAN atdurexy uoyesado Zuunp pasoyuour Ajsnonuyuod jauueyp aug Snid FUNDIAN wucre c6e AAN wug9z 0St DAN wugze 0st gAn wug 6e 0ze WAN uon es do Zuunp pasoyuow Ajsnonuyuod spauueya mog PNJ JaMog AN asuodsa y pepadg 1042343 SI JAADYIYM MW 10 paajuesenS 0 F eANd 4 F endy 74D MS 0 W0 MW G raduey dD 1U3Ip p Aetdsiq x SuoT RITFDadg dIEMpILPT October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Physical Features The main physical features of the UV Power Puck and UVICURE Plus are shown in Figure 3 UV Power Puck me O es Front Back Figure 3 UV Power Puck and UVICURE Plus Physical Features 10 Page 30 October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 31 Appendix C Technical Data for Test Strips amp Reader This appendix contains technical data regarding the UV Process Supply Inc CON TROL CURE Rad Check test strips and reader SOURCE UV Process Supply Inc n d CON TROL CURE Rad Check System Instruction Manual Chicago IL Author UV PROCESS SUPPLY INC CON TROL CURE RAD CHECK SYSTEM INSTRUCTION MANUAL s PART M007 078
41. y measurements were entered into Microsoft Excel 98 Excel also calculated the averages standard deviations error and plotted the calibration charts The coated side of the strip can face either up or down in the strip reader when measuring the E extinction However it is recommended to follow the same measurement procedure to minimize operator to operator variability For the experiments described in this report the coated side of each test strip faced up 7 Results 7 A Test Strip Variation October 22 2000 Calibration and Analysis of Ultraviolet Radiochromic Strips Page 15 Some trial runs were performed using test strip samples from lots 160298 and 310399 After measuring the extinctions with the strip reader a large degree of variability was found for sample sets that contained strips from both lots Error analysis was done using the root sum squares RSS method with partial differentials and the Student t test with 95 confidence Thompson s Tau Rejection Criteria identified strips in 4 to 1 lot mixtures as outliers i e the data from the differing strip was eliminated For sample sets that had 3 to 2 mixtures Thompson s Rejection Criteria could not identify any strips as outliers When test strip variance was suspected 23 test strips from each lot 160298 and 310399 were evaluated using the HP UV Vis spectrophotometer to determine their sensitivity to UV A radiation The spectrophotometer uses very low intensity UV radiatio
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