A national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Pulse Analysis Spectroradiometer 

System for Measuring the Spectral 

Distribution of Flash Solar 

Simulators 

Preprint 

Afshin M. Andreas and Daryl R. Myers

To be presented at the SPIE Optics and Photonics 2008 Conference: 

Optical Modeling and Measurements for Solar Energy Systems II 

San Diego, California 

August 10–14, 2008 

Conference Paper 

NREL/ CP-581-43652 

July 2008 

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 
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Pulse analysis spectroradiometer system for measuring the spectral 

distribution of flash solar simulators 

Afshín M. Andreas*a, Daryl R. Myersa 

a

National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO, USA 80401 

ABSTRACT 

Flashing artificial light sources are used extensively in photovoltaic module performance testing and plant production 

lines. There are several means of attempting to measure the spectral distribution of a flash of light; however, many of 

these approaches generally capture the entire pulse energy. We report here on the design and performance of a system to 

capture the waveform of flash at individual wavelengths of light. Any period within the flash duration can be selected, 

over which to integrate the flux intensity at each wavelength. The resulting spectral distribution is compared with the 

reference spectrum, resulting in a solar simulator classification. 

Keywords: spectral distribution, solar simulator classification, flash solar simulator, pulse measurement system, 

waveform capture, spectroradiometer, monochromator, artificial light 

1. INTRODUCTION 

Artificial sources of light, filtered to match an Air Mass 1.5 reference terrestrial solar spectral distribution, are used 

extensively in photovoltaic (PV) module performance testing. These machines are also used in PV plant production lines 

to test each individual module and generate a label with the module electrical performance. Flashing units are used to 

avoid heating the module and maintain a fixed set of standard reporting conditions. Flashes may be of durations from 

0.25 milliseconds (ms) to 500 ms, depending on the design of the simulator. There are several means of attempting to 

measure the spectral distribution of a flash of light, including diode array spectrometers and filter radiometers. However, 

these approaches generally capture the entire pulse energy, despite the fact that measurement of the electrical 

performance parameters can be triggered to occur only over a very narrow portion of the pulse, typically at the pulse 

peak. At the National Renewable Energy Laboratory (NREL), we have developed the Pulse Analysis Spectroradiometer 

System (PASS) which is capable of measuring the absolute spectral content of pulsed light sources (or continuous light 

sources) with traceability to the National Institute of Science and Technology (NIST). For pulse light sources, the 

NREL developed software allows any period within the flash duration to be selected over which to integrate the flux 

intensity at each wavelength. The resulting spectral distribution is compared with the reference spectrum, resulting in a 

classification of the quality of the flash solar simulator spectral distribution. 

This is especially important for technologies such as photovoltaics, where the appropriate design of PV devices (and 

knowing their efficiencies) depend on knowing how the devices respond to wavelength ranges in the solar spectrum (or, 

in this case, to a simulated solar spectrum). These measurements require advanced techniques compared to the 

measurement of continuous light sources; flashes are on the order of milliseconds long, so the instrument must be 

capable of either capturing an entire spectrum or recording the spectrum one wavelength at a time within the period of 

one pulse. Most commercially available spectroradiometers are incapable of making these measurements. 

The data from the PASS can be used for many applications, including: American Society for Testing and Materials 

(ASTM) classification of the simulator, spectral mismatch corrections, effect of lamp and filter aging, effect of different 

optical environments on the spectra at the test plane, spectral changes within the pulse period, and the effect of lamp 

input current or voltage. 

*afshin_andreas@nrel.gov; phone (303) 384-6383; fax (303) 384-6391; www.nrel.gov/solar_radiation

1 
2. HOW SPECTRAL DATA IS COLLECTED 

The PASS spectral data is collected like any conventional grating-based monochromator system except that the data is 

acquired with a very high speed data acquisition system that is synchronized to the pulses generated by the solar 

simulator. 

In a conventional grating-based monochromator like the PASS, light enters an integrating sphere that diffuses the light 

and makes it uniform; the integration sphere has a field of view of nearly 180 degrees. The light then enters the 

monochromator system. Inside the monochromator, the light hits a diffraction grating which disperses the light into its 

individual wavelength components. Depending on the position of the grating (which is controlled through software), a 

certain wavelength of light will be directed at a detector, such as silicon, which will then produce a current proportional 

to that light. This current is then measured at each wavelength by a data acquisition system and is converted to 

engineering units using a calibration file for spectroradiometer. Typically a grating-based monochromator includes an 

order sorting filter to reject higher order magnitudes of light dispersed by the grating. These filters are usually long pass 

filters; however, NREL uses band pass filters in the UV to help reduce stray light. Depending on the wavelength range 

of the monochromator system, the instrument may include several gratings mounted on a turret because a single grating 

is not capable of large wavelength ranges, such as 300–1800nm. When a particular grating reaches its maximum 

effective wavelength limit, the software will switch to the next grating. The same is true for detectors; the system may 

start with silicon and then switch another detector, such as germanium or InGaAs in the infrared. The spectral 

bandwidth of the monochromator is determined by the slit width and the grating dispersion. The slits are placed at the 

entrance of the monochromator (after the integration sphere) and the exit (just before the detector). NREL typically 

configures our instruments to have a spectral bandwidth of 1 to 5nm. 

3. PASS DETAILS 

The two major components of the PASS are a monochromator system and a data acquisition system. The 

monochromator system is composed of a grating-based monochromator (with one to three gratings), integration sphere, 

order sorting filters, one or two detectors (behind the monochromator), and a broadband silicon detector which is used as 

a trigger and a stability monitor. The data acquisition system is composed of high bandwidth amplifiers, high speed 

analog-to-digital converter (digitizer), and NREL developed software running on a laptop computer. 

The software can be configured to scan over a certain wavelength range, such as 280–1720nm at 5nm intervals (for a 

dual detector system). When the scan starts, the monochromator is positioned at 280nm and waits for a trigger signal 

from the broadband silicon detector. When light source flashes, the trigger is received and it will then acquire data for a 

specified time, which is long enough to capture a single pulse from the simulator. The software will then average the 

data over the specified region of the pulse (such as the peak or the flat top region). The software then applies a 

calibration factor to that data point which results in the absolute spectral irradiance at 280nm. The system then advances 

to the next wavelength and this process continues, until the scan is complete. The system will also use the broadband 

detector as a stability monitor for the light source and will correct the spectral data based on any broadband variation 

throughout the scan. 

The software will save the high resolution spectral data to a text file, which then can be used to classify a simulator for 

spectral match according ASTM E-927. [1]

Typically for a multi-pulse simulator, such as those made by Spire, a full scan takes 2–5 minutes depending on the 

wavelength range of interest. However, flash simulators that require cooling and/or charging time between flashes, such 

as Spire’s long pulse simulators, can take as much as 45 minutes or more, depending on the wavelength range and delay 

between flashes. 

The PASS has been calibrated using a NIST FEL lamp standard at the NREL Optical Metrology Laboratory. This 

calibration process produces a data file that represents the instruments absolute spectral response at each wavelength. 

2 
The calibration process also includes calibrating the wavelength drive of the system, so that it is within approximately 

1nm of known emission line outputs from mercury (Hg) or xenon (Xe) sources. 

3.1 Unique features 

What makes the PASS unique is its ability to measure the absolute spectral irradiance of a pulsed light source at any 

region within the pulse profile. Most commercial systems, which are actually capable of measuring a pulse light source, 

do so by either averaging or integrating all the data under one or more pulses. Also they may not have a way of 

triggering the systems reliably; not having a trigger can sometimes make it harder to capture the pulses from a simulator 

that does not rapidly flash multiple times during the systems acquisition period. Most of these commercial systems are 

only able to measure relative spectrum, whereas the PASS will give you absolute readings in units W/m2

/nm. 

Since the PASS is a grating-based system, it requires several hundred flashes to complete a spectral scan. Another 

unique ability of the PASS is that it can correct for any minor broad band variation of the light source that occurs during 

the scan, whether it is a flash or continuous simulator. NREL has yet to find any commercial grating-based 

monochromator systems that have this feature included. 

3.2 PASS flexibility and capabilities 

The PASS software was designed to allow the most flexibility with both automated and manual control of the 

instrument. All the monochromator components are stored in a configuration file in order to allow different systems to 

be built with different capabilities. This file includes information such as detector, grating, and filter quantities, 

including the wavelength at which these components should be automatically put into effect. Two PASS units have been 

made by NREL; one for NREL and one for Spire Solar, each with their own capabilities in terms of wavelength range. 

The software also includes a “Wizard” feature to quickly initiate scans for common measurement tasks. 

The software has many on-screen tools to view and analyze the data while data acquisition is taking place, to assure that 

measurements are being done with the proper simulator and/or PASS configurations. This is especially important when 

doing measurements on a slow-firing pulse solar simulator, such as Spire’s Long Pulse Simulators, which can take up to 

45 minutes to measure. During a measurement, the user can view the current spectrum as it’s collected and compare that 

spectrum with any previously measured data. After the scan is complete the user can view the ASTM E-927 

classification of the solar simulator. Spectral data is automatically saved to disk for later analysis. 

Prior to measuring a pulsed solar simulator, the user must determine where data should be taken on the pulse profile— 

typically on the peak of bell shaped pulses and across the flat portion of flat-top pulses. Once this is determined, the user 

can save this configuration for future measurements made on that simulator (or any other simulator with the same pulse 

characteristics). If necessary, the user can repeat this process for other simulators that have different pulse profiles. 

Now the user can quickly make pulse simulator spectral measurements using a list of pre-determined positions. The user 

can also view the pulse data during spectrum acquisition and has the option of saving the pulse data for later analysis, 

such as computing the spectrum at different times within the pulse profile. 

4. PASS HARDWARE 

The PASS is composed of many off-the-shelf components, which are mentioned later in this document; however, this 

does not imply endorsement by the United States Department of Energy or NREL. Due to the complexity of measuring 

the spectrum of pulse light sources, strict requirements were set for the selection of hardware that comprises the PASS. 

Complete control of the monochromator components and access to the raw signals from the detectors behind the 

monochromator was essential and, since the PASS was to be used to measure light pulses as short as 250 microseconds, 

the detectors needed a fast response time. Such fast detectors could include silicon, germanium, indium gallium arsenide 

(InGaAs), or a photomultiplier tube (PMT). Fig. 1 shows the schematic diagram for the dual detector system used at 

NREL. 

3 
Integrating

Sphere Optic

Input

Broadband

Detector

Silicon Detector

Amplifier*

Amplifier*

Monochromator

TE Cooler

InGaAs Detector

NI PXI Chassis

PASS Schematic

Flashing or Continuous

Light Source

NI GP BI Inter af ce

AC Adapters

AC Power

AC Adapter

AC Power

Cornerstone 260

Low Noise BNC Cable

Low Noise BNC

BNC Cables

GPIB Cable

Broadband Load

TE Cable

Filter Wheel

Filter Wheel Cable

Fixed Slit

Control Cables

Signal Cables

Power Cables

PASS v2.1 Dual 2-15-2008

Fixed Slit

(3) Automated Gratings

and Detector Selector

NI PXI ExpressCard

PASS DAQ Laptop

PXI Cable

Fixed Slit

NI 2 C- h. Digitizer

Ch. 0

Ch. 1

NI Multiplexer § BNC Cable

BNC Cable

Equipment on this side should be at and/or near light source

Equipment on this side of line are at a more remote location

AC Adapter Resistor Box

§ NREL is currently using an external USB off-brand multiplexer, 

what is shown represents any future systems.

NREL developed software

Drawn by: Afshín M. Andreas, NREL

*Amplifiers may be attached to monochromator

mounting plate. Ground wire connects

amplifier and detector cases.

 

Fig. 1. Schematic for the dual detector PASS which has a wavelength range of 280 to 1720nm at 5nm intervals.

4 
4.1 Monochromator 

For the monochromator, NREL selected the Oriel Cornerstone 260 monochromator from Newport. This monochromator 

was chosen because it allows control of the grating, filter wheel, detector selector, and shutter through simple commands 

using the GPIB or RS-232 interface. It allows up to two detectors and up to three gratings on the turret, that allow a 

wide range of spectral measurements from 250 up to 2800nm. Newport also has a wide variety of available components 

for the Oriel monochromators. 

4.2 Detectors 

The Cornerstone 260 monochromator supports up to two detectors. NREL is using the Oriel UV-enhanced silicon 

detector for wavelengths between 280 and 1100nm, for measurements beyond 1100nm a second Oriel InGaAs detector 

is used. Silicon has a temperature dependence above 1000nm, therefore if that wavelength region is required, then a 

Termo Electrically Cooled (TEC) detector must be used. Since the TEC is also required for the InGaAs detector, on 

NREL’s dual detector system, it is configured to cut-on at 1000nm, therefore the TEC is not necessary for the silicon. 

4.3 Detector amplifiers 

Since the detectors are behind a monochromator that has a spectral bandwidth of 5nm or smaller, the output currents 

generated by the detectors are very small, in the order of nanoamps. Therefore a very high gain amplifier will be 

needed. NREL has tried several off-the-shelf transimpedance amplifiers and found that many did not have the 

bandwidth requirements necessary for measuring short duration pulses of 1 ms or less at the high gains of 107

 or 108

volts/amp needed. Many of these amplifiers will distort the width and heights of the pulse, which can lead to erroneous 

measurements. The amplifier that was chosen for the PASS was the variable gain Femto DLPCA-200, which has the 

bandwidth requirements to measure such short duration pulses. It also has the advantage of being variable gain, for 

measurements on NREL’s High Intensity Pulse Solar Simulator (HIPSS). Although most measurements are typically 

performed at 1 sun, which would only require a fixed gain, the HIPSS, depending on the voltage setting, can range from 

several suns to several hundred suns, which would require a variable gain amplifier on the PASS. 

4.4 Data acquisition and software 

The data acquisition and software parts of the PASS are all from National Instruments line of products, due to NREL’s 

familiarity with their vast assortment of product offerings. Criteria for the PASS data acquisition include: 1) 1 MHz 

sample rate, 2) 16-bit vertical resolution or more, and 3) the capability of sampling at least two channels simultaneously. 

Based on the product selection, NREL is using the NI PXI-5922. The PXI-5922 is mounted inside a small PXI chassis 

which allows for other components to be installed, such as a GPIB adapter and a signal multiplexer. The PXI chassis is 

then attached to a notebook computer by an ExpressCard (or a PCMCIA/PC-card in older models). The PXI chassis 

then acts as an extension to the PCI or PCI-express bus of the computer and the chassis itself is transparent to the 

operating system. 

The software was developed exclusively in National Instruments LabWindows/CVI, which allows for sophisticated 

graphical interfaces with robust control of instrumentation, all of which is programmed through C code. 

5. PASS CALIBRATION AND PERFORMANCE TESTING 

NREL performs regular in-house calibrations of spectroradiometers with traceability to the National Institute of Science 

and Technology (NIST). The PASS is calibrated on a 6-month or an as-needed basis in NREL’s optical metrology 

laboratory, according to ASTM E-138-96. We purchase Spectral Irradiance Standard Lamps directly from NIST. These 

lamps come with a data sheet that lists the spectral irradiance of the lamp at various wavelengths in the wavelength range 

of 250 to 2400nm. [2]

The PASS calibration is performed using the continuous measurement mode, where the system averages the signal data 

for an entire second at each wavelength, and then computes a calibration factor based on the NIST provided irradiance at 

that wavelength divided by the measured signal in amps from the detector. 

5 
After calibration, the system is verified by measuring a 150-watt Oriel Simulator and a Spectrolab Large Area 

Continuous Solar Simulator (LACSS) and comparing the results with measurements made by an Optronic Laboratories 

OL750, which is also calibrated at NREL. The measured spectrum of the PASS agrees to within 2% of the OL750. [Fig. 

2] 

0.01

0.1

1

10

300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

Wavelength (nm)

Absolute Spectral Irradiance (W/m2/nm)

NREL PASS

Optronic Labs OL750

Fig. 2. PASS measured spectrum of continuous Oriel Solar Simulator Model 66902 (unfiltered) compared to OL750.

The repeatability of the PASS measurements are checked with continuous light sources, such as the NIST FEL lamps, 

Oriel, and Spectrolab simulators. The repeatability of the PASS (and light sources) was +/- 0.2 % for the FEL lamp and 

the simulators were approximately +/- 1%. [Fig. 3] 

0.95

0.96

0.97

0.98

0.99

1

1.01

1.02

1.03

1.04

1.05

300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

Wavelength (nm)

Ratio

Ratio of two NREL LACSS Measurements

Ratio of two Oriel SP93194A Measurements

Ratio of two NIST FEL Lamp Measurements

Fig. 3. PASS repeatability testing with continuous light sources. NIST FEL lamp shows +/- 0.2 % repeatability.

Once the calibration and repeatability was verified with continuous sources, it was then verified using light sources for 

which it was primarily designed for—pulsed light. We measured the NREL Spire SP240A pulsed simulator. This 

simulator has known problems with the flash-to-flash repeatability; therefore as the spectrum was being measured (one 

flash per wavelength) the broadband intensity of the light was fluctuating by +/- 5% resulting in the ratio of the two 

spectral scans differing by as much as +/-5% or more. However, since the PASS has the ability to automatically correct 

the spectral data due to broad band intensity instability, the ratio of broad band corrected spectra agreed to within +/-1%. 

[Fig. 4] 

6 
0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

1.06

1.08

1.1

350 450 550 650 750 850 950 1050 1150 1250 1350 1450 1550 1650

Wavelength (nm)

Ratio

Ratio of two spectral scans corrected for broadband variability

Ratio of two spectral scans

Fig. 4. PASS repeatability testing with SP240A pulse solar simulator. Thicker line shows broad band corrected spectral 

ratios.

To verify the pulse measurement capability the spectral measurements are compared to an Optronic Laborories OL750 

running in pulse measurement mode (PMM). The OL750 PMM is not capable of taking data on the peak of the pulse, it 

simply integrates the entire energy in one or more pulses over a specified time. Therefore the PASS is configured so that 

it acquires data during an entire pulse for this comparison. The measured spectrum of the PASS agreed to within 2%–5 

% of OL750 [Fig. 5]. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

Wavelength (nm)

Normalized Spectral Irradiance

Optronic Labs OL750

NREL PASS

Fig. 5. PASS measured spectrum of SP240A compared to OL750 PMM.

Now that that pulse measurement capability of the PASS has been verified, the software can be configured to acquire 

data only on the peak of the pulse, where the measurements of a typical PV device is normally tested on a pulsed solar 

simulator. 

This shows that measuring the entire pulse, rather than the preferred peak, results in a spectrum that is 2%–4% low for 

wavelengths less than 800nm for this type of pulsed simulator. [Fig. 6] In most cases this can be considered negligible 

if the only intent is to produce a classification for the simulator, because the ASTM E-927 allows up to +/- 25 % 

deviation from the reference spectrum to still be considered Class A for spectral match. [1]

7 
0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

Wavelength (nm)

Normalized Spectral Irradiance

peak of pulse (0.25 ms wide)

entire pulse (1.2 ms wide)

2 - 4% decrease observed

Fig. 6. Effect on spectrum when measuring using entire pulse results in a 2%–4% lower intensity for wavelengths below 

800nm. The two spectrum required area normalization, because data is being averaged on rising and trailing edge of 

the pulse which reduces the overall measured intensity. For this test the spectrum at each wavelength was captured 

only once, then a spectrum was computed using the entire pulse (1.2 ms wide) and then at the peak (0.25 ms). This 

would remove any affects due to repeatability of the solar simulator or the PASS. 

This test was also performed on Spire SP3500 Multi Pulse and a SP4600 Single Long Pulse (SLP) and the same results 

were observed. 

6. SPECTRAL MEASUREMENTS PERFORMED BY NREL USING THE PASS 

NREL has used the PASS to measure the spectrum of at least 13 different pulse solar simulator models from 

manufacturers including: Spire Solar, Spectrolab, Berger Lichttechnik, and Spheral Solar. The pulses from these 

simulators were as small as 0.25 ms bell shape curves to as large as a 100 ms flat top pulse, two example pulse shapes 

from NREL simulators are shown in Fig. 7. 

8 
0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time (ms)

Normalized Signal

NREL HIPSS

NREL SP240A

Fig. 7. Example pulse profiles from NREL solar simulators. Bell shape curve is from SP240A and flat top is from HIPSS.

The PASS has been used to measure and classify solar simulators for spectral match under the ASTM E-927-04. This 

includes both in-house simulators and at least eight outside companies. The Spire SP240A at NREL and the Spire 

SP660 at the Florida Solar Energy Center (FSEC) are measured annually using the PASS. The following is an example 

ASTM E-927 chart showing that the SP240A is Class A for spectral match [Fig. 8]. The spectral data is compared to the 

reference global spectrum in ASTM G-173. [1] [3] 0.1840.199 0.184

0.149

0.125

0.159

0.144

0.177

0.193

0.200

0.139

0.147

0.143

0.137

0.146

0.177

0.193

0.203

0.000

0.050

0.100

0.150

0.200

0.250

0.300

400-500 500-600 600-700 700-800 800-900 900-1100

Wavelength bin (nm)

Fractional Contribution (400 nm - 1100 nm)

ASTM G-173 Global w/Class A Limits

NREL SP240A AUG-2005

NREL SP240A AUG-2004

Fig. 8. ASTM E-927-04 spectral classification of NREL SP240A pulse solar simulator from August 2004 and 2005. Error 

bars on G-173 reference spectrum are permitted deviation under ASTM E-927 for Class A. Error bars on measured 

data is the measurement uncertainty of the PASS.

9 
NREL has performed numerous spectral measurements of the NREL High Intensity Pulsed Solar Simulator (HIPSS) 

using the PASS. One study was performed by running the simulator at seven different voltages, which corresponded to 

approx. 20 to 300 sun intensity on the test bed. These tests showed that the spectrum at low voltage were dominated by 

xenon emission spikes, however at higher voltages these spikes were indistinguishable from the rest of the spectrum. 

[Fig. 9] 

Fig. 9. Normalized spectral curves at different HIPSS lamp voltages, showing Xe emission spikes diminish at high voltage.

These spectral shifts were also demonstrated using the ratio of short circuit current densities from single junction cells in 

a typical triple junction cell. As the voltage increases, the ratio between the junction types shifted, signaling a change in 

the spectral content of the flash, due to differences in the spectral response of each cell. [4]

Studies were also conducted to determine whether or not there was a spectral shift over the life of an individual pulse. 

This showed that energy toward the end of the pulse contained more infrared than ultraviolet. [Fig. 10] 

Fig. 10. HIPSS pulse profiles at different wavelengths, showing that UV is reduced toward the end of pulse life.

10 
11 

7. FUTURE WORK 

The PASS has gone through improvements and upgrades since it was first developed and there is still room for 

improvement. The current InGaAs detector is limited to 1700nm and there is desire at NREL for spectral data beyond 

that. Since the detector must have a very fast response, an Extended IR InGaAs detector may be purchased soon to 

allow measurements up to 2200 to 2400nm. 

One disadvantage of the PASS is performing routine measurements on slow-firing pulse simulators. Depending on the 

simulator flash rate, the measurement could take up to several hours. An example of this is the NREL HIPSS, which 

requires 1 minute cool time between each flash. A full, high resolution measurement from 300nm to 1700nm at 5nm 

intervals takes up to 280 minutes to perform. Most pulse simulators, like the multi-pulse Spire solar simulator, takes just 

under 5 minutes to measure. To improve the speed of the PASS, a diode array would be necessary so that the spectrum 

can be measured in one flash, rather than one flash per wavelength. In order to reach the wavelength range desired, both 

a silicon and InGaAs array would be required. Due to possible accuracy issues, the diode arrays were not pursued in the 

original development of the PASS. 

There also has been commercial interest in the PASS, which could yield further improvements and expose the system to 

a broader user base. 

8. SUMMARY 

The PASS has proved to be an invaluable resource to both NREL and industry for evaluating the spectral content of 

pulse solar simulators. The data from the PASS has many uses and the system can be tailored to most measurement 

needs. Future improvements to the system could yield a wider wavelength range, as well as the possibility of acquiring 

the spectrum at a more rapid rate. 

ACKNOWLEDGMENTS 

The authors would like to thank Ted Cannon, who designed the first PASS unit for which this new and improved system 

is based on; Keith Emery, who provided many suggestions on how to improve the operation and accuracy of the system; 

and the NREL Photovoltaic Performance and Characterization Team, who allowed us extensive use of their pulsed solar 

simulators during the development and testing of the PASS. This work was supported by the U.S. Department of Energy 

under Contract No. DE-AC36-99GO10337 with the National Renewable Energy Laboratory. 

REFERENCES 

[1] ASTM Standard E-927-04, “Standard Specification for Solar Simulation for Photovoltaic Testing,” ASTM 

International, West Conshohocken, PA, www.astm.org. [2] ASTM Standard E-138-96, “Standard Test Method for Calibration of a Spectroradiometer Using a Standard Source 

of Irradiance,” ASTM International, West Conshohocken, PA, www.astm.org. [3] ASTM Standard G-173-03, “Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and 

Hemispherical on 37° Tilted Surface,” ASTM International, West Conshohocken, PA, www.astm.org. [4] J. Kiehl, K. Emery, and A. Andreas, “Testing Concentrator Cells: Spectral Considerations of a Flash Lamp System,” 

Proc. 19th European PVSEC, 2463-2465 (2004). 
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2. REPORT TYPE

Conference Paper 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Pulse Analysis Spectroradiometer System for Measuring the 

Spectral Distribution of Flash Solar Simulators: Preprint 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

A.M. Andreas and D.R. Myers 

5d. PROJECT NUMBER

NREL/CP-581-43652 

5e. TASK NUMBER

PVB77301 

5f. WORK UNIT NUMBER

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

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

8. PERFORMING ORGANIZATION

REPORT NUMBER

NREL/CP-581-43652 

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

NREL 

11. SPONSORING/MONITORING

AGENCY REPORT NUMBER

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

Flashing artificial light sources are used extensively in photovoltaic module performance testing and plant production 

lines. There are several means of attempting to measure the spectral distribution of a flash of light; however, many of 

these approaches generally capture the entire pulse energy. We report here on the design and performance of a 

system to capture the waveform of flash at individual wavelengths of light. Any period within the flash duration can be 

selected, over which to integrate the flux intensity at each wavelength. The resulting spectral distribution is compared 

with the reference spectrum, resulting in a solar simulator classification. 

15. SUBJECT TERMS

spectral distribution; solar simulator classification; flash solar simulator; pulse measurement system; waveform 

capture; spectroradiometer; monochromator; artificial light 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT

UL 

18. NUMBER 

OF PAGES 

19a. NAME OF RESPONSIBLE PERSON 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified

c. THIS PAGE 

Unclassified 19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18