Solar Radiation FAQs
Are you on GSA or government pricing?
No, we are not on GSA or government pricing.
Yes, absolutely. For radiometers such as the UVB-1, MFR-7, UVMFR-7 and SPUV-10, the YESDAS supports automated remote unattended operation. However, depending on the number of instruments, you will likely want to order the PCMCIA-2 memory card option.For our TSI and RSS instruments, you can expect to collect anywhere from 1 to 32mb of data per day, depending on data rates. Thus a local PC or a 24-hour, 7 day a week Internet connection is good to have. In cases where it is infeasible to have a network connection, the TSI-880's optional DSM-420 data storage module supports 420Mb of removable storage.
This is a rather complicated area of radiation physics. First of all, you don't calibrate broadband UVB-1 instruments using irradiance standard or arc lamps. The spectral output of FEL lamps is wildly different than the solar spectrum. What you do is calibrate a spectroradiometer using a FEL lamp, then you co-locate the spectroradiometer with a pool of about five closely matched broadband instruments and using the sun, transfer the calibration (a UVRSS or U-1000 will work for this, in the past we've also used Richard McKenzie's own spectroradiometer as a check). Please direct them to chapter 4 of the attached UVB-1 manual which outlines the procedure. You should read this before meeting with them. This will be far more expensive path if they do not own a UVRSS-1024. In some real sense this is a very good reason to buy a UVRSS, it permits you to derive calibration constants directly, (using the same transfer source, the sun). We sell the PFC-5001 lamp calibrator as an accessory to the UVRSS (does not work standalone).
Most users pay us the cost to calibrate them at the factory. NIST/PTB/NPL are highly competent labs, but it will be expensive. In the US the specific NIST lab to talk to is the CUCF - have them look at: http://www.srrb.noaa.gov/calfacil/cucfhome.html CUCF calibrates all of the USDA's broadband UVB-1s for Colorado State (who runs the US Dept. of Agriculture's UV-B monitoring program.)
The UVRSS can produce ozone data (see page 3-23 of the manual for information). We have compared the UVRSS favorably with Dobson measurements taken near Boulder, Colorado.
This is happening near summer solstice ... it is not adjusted correctly. This will create significant, non-correctable measurement errors to direct-and-diffuse around solar noon. Here are some things to try to get it aligned:
- Using a protractor, cut a small (roughly 3") triangle of thin cardboard with the angle of your site latitude. Now slip the triangle under the motor case between the stand and the motor housing, to verify your motor's shaft angle is equal to your site latitude. Has to be within about a degree, once set you can forget it. I realize you said you did this, but verify it.
- Check that your motor assembly is pressed all the way back against the machined slide (a both points top and bottom), If there is a small gap loosen the screw and press the motor hard against the slide and re-tighten the clamp.
- Use a bubble level to verify that the diffuser is level in both planes. Do not let the bubble level come in contact with the white diffuser, which is soft. Do not worry about the level of the base itself, you want to check the level right at the black diffuse ring.
- Assuming the above three items are set correctly, the band may have been bent slightly out of round. Gently bend it down (not too much). Do this around solar noon.
Each MFR is characterized yearly in our optical calibration facility, in four ways:
- A North/South angular scan (via a cosine bench)
- An East/West angular scan ( " )
- Relative spectral filter function response (via a monochromator) and channel dark levels
- Absolute voltage response (via a NIST traceable irradiance standard lamp)
The actual MFR head characterization takes three steps:
- North/south and east/west angular measurements of an MFR head are done at 1 degree increments from -90 to +90 degrees off axis. The measurements are taken at a special cosine test facility, using a 500 watt lamp mounted 5 meters form the turntable. This generates your solarinfo (.sol file) that permits angular correction. In this step we characterize the angular effects of the diffuser that are so critical to doing the direct-normal calculation and for Optical Depth accuracy.
- Next, a spectral scan of the head is done. The head is put in front of a 150 watt lamp fed monochromator which sweeps over the bandwidth of each filter passband at 1 nm increments. This is a "relative spectral response test"
- Finally, we put the MFR head in front of a 1000 watt quartz halogen tungsten filament lamp (50 cm distant) and get the absolute voltage sensitivity of the channel. Using the bandpass determined in Step 3, along with the lamp's table of irradiance outputs, we calculate the actual engineering constants to get you from volts out to w/m^2/nm.
This is clearly a system setup/alignment issue. Even if a shadowband correctly shades later at a different time of year, it was not", something is not aligned. Check the following:
- YESDAS time is set precisely within a few seconds of GMT -Aligned geographical north/south (and verified at solar noon?) -Level the diffuser (not via the bubble level at the base, check the black diffuser ring itself with a machinist's level)
- Verify motor angle with a paper template (and verify the motor is pushed into the slide fully and bolts are snug)
- Verify band stops at nadir location (use your thumb/forefinger)
- Was band bent in shipment? (use a paper template)
What is the backup power requirement and temperature sensitivity of the RSS or UVRSS?
The DC standby battery keeps the RSS/UVRSS power bus and CPU/detector solid. However, the spectrograph thermal stabilization heaters are on AC, so these are not backed up. If the internal temperature drops due to an AC failure, the unit will shut down in a few minutes to prevent wavelength measurement errors or water from condensing on the optics. Short AC power glitches are OK, but not day long outages. When equipped with the internal data module, the RSS will hold data until you get power back on. The power management methodology was tested extensively on the MFR and it works well. The RSS optics are thermally stabilized with approximately 100 watts of heat, and the instrument is well insulated. Its temperature sensitivity is so small that we cannot measure any at this time.
What is the optical design and type of detector (CCD) used in the RSS and UVRSS?
The RSS family uses a unique locked-down spectrograph optical dispersion design via a fused silica prism as the refraction method. The UVRSS covers from 290-360 nm and the visible/NIR RSS covers 360 to 1100nm. Both the UVRSS and the RSS have astronomical-quality, slow scan, 1024-element CCD image detectors. These are electronically cooled for low noise performance. Other spectroradiometer designs have relied on moving parts to adjust ruled diffraction gratings. With the RSS/UVRSS, however, there are no internal moving parts that control throughput or wavelength registration (other than the shutter which is only used for dark level measurements.) This results in superior optical performance and rugged durability.
What do I need to know before selecting a radiometer for outdoor use?
You need to know whether you want spectral or broadband data, and whether you want measurements in the thermal Infrared, NIR/visible, UV-A or UV-B.Next, decide whether you want direct-normal and/or total (global) radiation measurements.
Finally, decide if you need continuous unattended measurements of "campaign mode" measurements. In campaign mode, the instrument is kept out of inclement weather and setup for brief periods of time, such as making ground-truth measurements during a satellite fly-by. All YES systems work well in both applications because they are weatherproof and thermally stabilized. However, other instruments (e.g. telescopes) are only suitable for campaign mode.
The internal operating temperature of the UVB, MFR, UVMFR, SPUV, RSS is about 45° C. Why is this?To eliminate effects of changing ambient air temperature and solar loading, we thermally stabilize the internal optics of our instruments to above ambient temperature, between 38° C and 45° C, depending on the instrument. The exact temperature is not as important as knowing that the temperature is stable and has been stable since the most recent calibration.
No (this is why we have separate products). An MFR-7 measures optical signals at a different order of magnitude than does the UVMFR. Hence the internal design of these two instruments is vastly different. Measuring UV requires a much higher gain level to measure the much smaller signals present. A SPUV, however, can be setup to cover from 300 nm all the way to 1040 nm.
Can longer cables be supplied?
Yes. The standard length cable on a UVB-1, UVA-1, or TSP-700 is 10 meters, and standard cable for the TSP-400 is 3 meters. However, we can supply a longer cable as a special order. You can also splice a piece of good-quality foil shielded cable to the existing cable. The cable type that we use is manufactured by Belden, but any PVC jacket cable with foil shield and drain wire, plus nine #24 AWG stranded tinned copper conductors, will work.Note that due to signal levels, the cable on the MFR-7 or SPUV cannot be made longer than the standard length.
Any meteorological sensor with either a voltage current or digital (TTL) pulse type output (but not RS-232) can be added. The YESDAS-2 manual covers this subject in detail.
Can additional weather sensors be added to the MFR/UVMFR, SPUV or YESDAS-2 logger?
Yes. Since the MFR-7 occupies only 8 channels and YESDAS-2 has 32 analog and 6 digital inputs, you can connect up to 24 other auxiliary inputs. We have supplied systems with SPUV-10's and MFR-7s from a single YESDAS-2. Depending on the number of sensors and the sampling rate, you may also want to order a memory card option to hold all the data that the sensors create.
Is it possible to mount the MFR-7/UVMFR vertically or upside down?
Yes, but if you mounted the MFR-7 up side down the shadowband cannot be used. If you want upwelling radiation our Model DFR-7 up/downward looking dual head system is an excellent solution. The down-looking radiometer is a MFR head, while the a second MFR-7 head with shadowband looks up to measure direct, diffuse and total horizontal. In broadband pyranometery these differential measurements are typically made by an instrument called an "albedometer".
Yes. If, for example, you change MFR/UVMFR filters, you will likely want to have us do a "before and after" calibration. That way you can see the effects of the new changes. The cost for this work is double the cost of a single characterization.
This tends to happen near summer solstice and is an adjustment issue:
- Using a protractor, cut a small (roughly 3") triangle of thin cardboard with the angle of your site latitude. Now slip the triangle under the motor case between the stand and the motor housing, to verify your motor's shaft angle is equal to your site latitude. This must be set to within about a degree, and once set, you can forget about it.
- Check that your motor assembly is pressed all the way back against the machined slide (at both points top and bottom), If there is a small gap, loosen the screw and press the motor hard against the slide and re-tighten the clamp.
- Assuming the above two items are set correctly, the band may have been bent slightly out of round. Gently bend it down (not too much) and try that.
Each MFR is characterized yearly in our optical calibration facility, in four ways:
- A North/South angular scan (via a cosine bench)
- An East/West angular scan ( " )
- Relative spectral filter function response (via a monochromator) and channel dark levels
- Absolute voltage response (via a NIST traceable irradiance standard lamp)
The actual MFR head characterization takes three steps:
- North/south and east/west angular measurements of an MFR head are done at 1 degree increments from -90 to +90 degrees off axis. The measurements are taken at a special cosine test facility, using a 500 watt lamp mounted 5 meters form the turntable. This generates your solarinfo (.sol file) that permits angular correction, In this step we characterize the angular effects of the diffuser that are so critical to doing the direct-normal calculation and for Optical Depth accuracy.
- Next, a spectral scan of the head is done. The head is put in front of a 150 watt lamp fed monochromator which sweeps over the bandwidth of each filter passband at 1 nm increments. This is a "relative spectral response test"
- Finally, we put the MFR head in front of a 1000 watt quartz halogen tungsten filament lamps lamp (50 cm distant) and get the absolute voltage sensitivity of the channel. Using the bandpass determined in Step 3, along with the lamp's table of irradiance outputs, we calculate the actual engineering constants to get you from volts out to w/m^2/nm.
You have an early version of a .sol file. Simply add a 'B' to the LAMDAS between the M and D. The LAMDAS statement is located on the second line of the .sol file. You can open the .sol file for editing by browsing the "other files" tab in the data files window. Then double clicking your .sol file. Be sure to save the file. Do not change anything else in the .sol file.
What kind of optical interference filters do the MFR, UVMFR, and SPUV use?
The MFR, UVMFR, and SPUV all use new technology "Ion Assisted Deposition" interference filters. The slit width and effective center wavelength are exceptional and stable. However, while the throughput/transmission of IAD filters is far superior compared with previous generations of optical filter technologies, we still recommend yearly factory calibrations.
Can I get non-standard filters for the MFR, UVMFR, or SPUV?
Yes, at additional cost and only as long as the filters are 10 nm FWHM wide and in 10 nm increments. For the MFR-7 and SPUV, the longest practical wavelength is 1040 nm due to the silicon detector's lack of quantum efficiency beyond this. Remember that the radiometric calibration accuracy may suffer as the bandwidth increases. Beyond 40 nm wide, calibration with FEL lamps becomes a problem.The RSS/UVRSS instruments provide continuous spectral measurements and are excellent solutions for special requirements.
Can I replace my standard filters for custom MFR/UVMFR/SPUV filters later on?
Yes. You will also need to recalibrate at the time these factory modifications are made.
Can I connect a second MFR-7 head to the YESDAS-2 on my MFR/UVMFR system that we already own? What about adding a SPUV?
Yes, but only if it is a downward-looking head (this is our DFR system). You can also connect a SPUV to an MFR/UVMFR. For example, an existing MFR or UVMFR can add on a SPUV as a factory upgrade. Conversely, a SPUV/YESDAS-2 system can have an MFR-7/UVMFR instrument head added by the factory. However, it is not possible to connect two complete shadowband instruments, such as two MFR/UVMFRs, to a single YESDAS.
No. YESDAS-2 provides a sophisticated ephemeris algorithm, and thermal control to these instruments, and is therefore tightly coupled to their design. In addition, our multi-platform user software and our optical calibration facilities are dependent on YESDAS-2. Also, YESDAS-2 provides automated Langley analysis and optical depth capability. Keep in mind that the cost of the YESDAS is only a fraction of an MFR-7, UVMFR, or SPUV system, so any cost savings would be minimal.
How many other instruments can I connect to the YESDAS-2 supplied with my MFR-7, UVMFR, or SPUV?
The YESDAS-2 has 32 analog channels, with 8 of them taken up by an MFR-7 or UVMFR, or 11 channels for a SPUV-10. Assuming you want to monitor battery voltage, a MFR-7 or UVMFR can accept up to 23 other sensors; a SPUV-10 can handle 20 more. In addition six pulse/digital TTL counter inputs are available for anemometers or tipping bucket rain sensors. Adding several pyranometers or IR pyrgeometers is possible and frequently down for users that would like to integrate a MFR into their legacy BSRN-type tracking pyranometer installations.If you intend to connect the YESDAS-2 up to other instruments, please let us know at time of order so we can advise you.
Can I run systems in remote areas without AC power via solar panels?
Yes, but there are limitations in locations that are statistically cloudy. The UVB-1, YESDAS, MFR/UVMFR, and SPUV systems all run from DC power, but solar panels require a careful assessment of the total solar resource available at your site. The minimum number of available sunlight hours (shortest day of the year), along with the worst case total power (duty cycle) determines a PV or wind system size.
There are vendors who can provide turnkey solar power installations, or you could build this yourself. The solar cells are connected to a battery bank via a "charge control module", and the battery line is run to your instruments via YESDAS-2's battery connection. One such vendor is www.northerntool.com which is a good place to look for these components.
We have been careful to try to design all systems to run from DC power. However, some instruments such as the TSI and RSS require so much power (i.e. hundreds of watts) that running them off-grid is impractical. In these cases a small propane gas or diesel generator starts to make economic sense v.s large banks of solar panels.
How stable are your radiometric UV/Vis instrument calibrations?
In the April 1998 issue of the Bulletin of the American Meteorological Society a peer-reviewed paper describes the calibration stability of the US government's UV monitoring network over a four year period. This paper describes the long term calibration stability of approximately fifty YES model UVB-1, MFR-7, and UVMFR-7 instruments during a four year period, and concludes that the stability has been outstanding.
The MFR shadowband is rotating fully at night and not making the normal 3 stops, is this normal?This is normal operation. The MFR is designed to rotate continuously (without the 3 stops) at night. The reason for this is to keep the motor warm and dry. If the instrument is left off and not running for any length of time, the motor electronics can take in moisture from the night or rain.
Why did you change the MFR motor cable connector and how do I transport it?
In 2005 we improved long term system reliability by eliminating the corrosion-induced connector failures. We removed the motor connector, wiring the motor cable directly to the YESDAS. We recognize that this design change now mandates slightly additional human effort at setup time as you must thread the cable and connector into YESDAS. However, our service experience indicated two issues in support of this decision:
- Most MFR systems remain in fixed locations and once setup, remain in place
- Motor failures tend to be related to connector failure above all other factors
First of all, you need to solicit help from your local MIS/IT department and school electrician for this as it is a communications infrastructure issue. You have three options available to you:
1. Analog phone line: presuming a POTS phone line is present atop the mountain, install a V.90 telephone modem on the YESDAS and dial into it. The Remote PC also needs a modem and telephone line as well. In this case you must buy two USR modems and have tow analog phone lines installed.
2. TCP/IP: presuming you have an internet connection up there we sell an ethernet adapter that lets you plug
YESDAS into a RJ45 10BaseT LAN jack. The remote PC then runs a special software driver to virtualize its serial port such that YESDAS Manager "thinks it is cabled directly to YESDAS" and talks to it via TCP/IP. Price is about $500, and the advantage is you can have your MIS/IT folks handle the networking part. 3. Buy fiber optic modems and run fiber ethernet over the entire distance. This will be tremendously expensive. Q1: What is the total distance involved and how rocky is the soil (rock)? Q2: Is there an empty conduit available?
Note that you cannot simply leave fragile fiber lying out on the ground, or string it on poles, it needs to be well-protected. Note that there are also fiber optic-to-RS-232 conversion devices, however, they lack the hardware flow control lines which YESDAS needs. Although they work on simple three wire serial devices (like the MET-2010), they do not work on higher speed equipment. So this is why you need ethernet-over-fiber.
The more I think about this and your rocky soil situation, the more I think you should hire an electrician to run the AC to code. And then setup a dedicated point-to-point 802.11 WiFi link adjacent to your MFRSR pad (about 25' from it would be ideal to prevent RFI pickup).
You're going to regret that flexible conduit, it's fine for a few feet of AC feed from a switch box to a motor, but 500' is far too long unless it's very thick wire. There are many headaches with long AC feeds, especially the fact that they tend to pickup lighting ground surges unless they are in metal. You MUST encase the wire in metal conduit. And due to galvanized steel corrosion, and each 10' conduit section must be carefully grounded, such that each 10' section gets bonded to the next ... and a copper #6 AWG runs parallel to the whole thing, tying it all together. If you simply lay plastic conduit encasing a wire along the surface of the soil this will creates a huger radial antenna and you will inevitably pick up a nearby lighting ground stroke's ground surge inductively and it will destroy your MFRSR. This is why there's a ground rod at the base of many phone poles. And that's why you never see what you are describing done, the conduit gets installed BELOW ground.
Also, what is the IR^2 drop in the 500' AC feed? I presume you are putting in a dedicated, 110V/20A circuit, no? So #12 AWG is normal for 20A ... but not for 500'. If you do the calculation you're going to want something on the order of #8 AWG cable ... which is quite heavy stuff. You now need a 2" or 3" "flexible conduit" to pull that 3 conductor #8AWG through.
My point here is that you really need to engineer this utility installation. Saving 80% on labor is great, but not if the instrument gets destroyed in the process by lighting, AC voltage surges or sags. You are measuring picoamperes to femptoampere precision on a MFRSR, it MUST be properly grounded. Does the school have a licensed electrician on staff that can design this and sign off on the AC and ground system design?
We strongly advise NOT to use CAT-5 cable for that distance. We recommend a fiber-optic solution. This not only will ensure your data is properly transported, but will protect your Yesdas and MFR from electrical storms. That CAT5 cable will act like a lightening rod and damage your system.Black Box has serial to fiber converters. You will need one on each end. Then you have to lay the fiber. Make sure the converters support all hardware handshaking lines.
In short, I have installed a MFR-radiometer on the top of a mountain. I am trying to bring the signal down to a lab (500 feet max.) SI Tech electronics suggested the following: 1- 500 feet of outoor rated fiber optic cable( model 6002) 2- RS 232 ASYNC/SYNWe use the 2505 here. It works fine.
Yesdas Manager does not support any kind of moving or archiving files over a network. The only automated file functions built into it are deleting old raw files and processing and downloading files for viewing.
As I understand it, you really would like for the master server to be the place where everything is stored and viewed, and not have the files stored on the remote PC, or any clients viewing data there.
Two options that we can recommend:
- Write your own automation to transfer downloaded files from the remote site to the main site- this assumes the PC's are networked and you can set up some sort of file sharing or secure copy or FTP.
- Purchase a serial to Ethernet converter for the Yesdas. We do sell these, if you are interested. Or you can purchase one yourself- just ensure it supports full handshaking. You then do not even need the server PC at the remote site. You would use your main or "master" server to connect directly to the Yesdas via TCP/IP to control and download. The master server would run the converter's software and appear as a COM port to Yesdas Manager. You would want to probably put a bit of fiber in between the converter and Ethernet cable so that electrical storms don't take out your Yesdas or network.
The Yesdas Manager Manual has some good information on how to convert data into a usable format. Section 5 in particular explains how to process data. Page 5-25 REPEAT Section has the formula to convert to W/m2. The QED Program Editor is a another useful tool to checkout. Page 5-2 has an overview of the QED Program Editor.
We find when the band rotates non-stop like that, it's usually related to a hardware issue of some sort. We would recommend that the entire system (MFR, Yesdas, and Motor) be sent in for troubleshooting and repair.
The Yesdas uses the spreadsheet date format (days since Jan 1, 1900). However, the firmware for the Yesdas was developed on the Macintosh platform, and MS Excel for the Macintoch and MS Excel for Windows handle the first day of 1900 differently. On the Macintosh platform, the first day is day 1, whereas on the PC (Windows) platform the first day is interpreted as day 0. What you are observing is normal if you are on a MS windows PC, the time and date will be exactly one day behind what you expect.
The Yesdas always must be set at UTC time. It does not know about time zones or daylight savings time.
The Yesdas Manager software sets the clock of the Yesdas by using the PC's clock. It takes the time right from the PC, and uses the time zone offset defined in your control panel to calculate UTC time.
However, it sounds like your Yesdas time is drifting. How long has the Yesdas been running? Sometimes the Yesdas can loose time, and this may be what you are experiencing. You can compensate for this by using a software time adjust, as defined on page 4-16 of the Yesdas Manager manual.
But please be sure that when you are initilaizing the Yesdas, it is getting sent the right time from your PC. You may want to try to set your PC to UTC time.
Next to the place where I will position the SDR-1 I already have a computer on which Labview is running. I was wondering if there also is a labview VI to handle the data from the datalogger instead of the YESDAS manager software. If not, is it possible toThere are no VI's for the Yesdas Data Logger. You must use Yesdas Manager to download and extract the data, as it is in a proprierty format. However, once downloaded and extracted, you are able to output to ASCI for display in a spreadsheet or other program.Yesdas Manager does not need a dedicated computer, as long as a serial port is always available to it. It can not share a port with other programs. If you output PH meter and thermometer analog signals, the Yesdas and Yesdas Manager can log those along with the solar data from the SDR.
No. The spectral distribution of a lamp is very different than the spectral distribution of the sun, especially in the UV portion of the spectrum. The sun is essential in calibrating the absolute response of broadband instruments as a source of stable spectral irradiance.
You should first know that three different responses of broadband instruments are measured during calibration: the cosine response, spectral response, and the absolute response. This question refers only to the absolute response. For more in-depth information on calibrating the other responses, and on calibration in general, please click on Services, and then Optical Calibration.
UVB pyranometers are calibrated against both the sun and against specially calibrated UVB pyranometers known as transfer detectors. These instruments have been carefully calibrated against co-located narrowband spectroradiometers, which in turn are calibrated with NIST-traceable quartz halogen tungsten filament lamps in our Optical Calibration Facility. The transfer detectors can be used to calibrate instruments off-site, hence their name. Broadband visible Total Solar Pyranometers are calibrated against the sun and other co-located pyranometers which are ultimately traceable back to WMO standards located at the World Radiation Center in Davos, Switzerland.
Is it possible to have a single pyranometer that measures the combined UV-A and UV-B?
Yes, our model UVA-1 covers the entire UV-A and UV-B range of 280-400 nm ... but since only a tiny fraction of the integrated dose involves the UV-B range of 280-320 nm (compared with the total 280-400 nm range), what you are essentially measuring is UV-A.
Ideally you should use the tables and the solar zenith angle at the time of measurement. The origin of the multiply by 25 vs. divide by 40 is that some radiometers are calibrated in watts/m^2 while others are in calibrated in microwatts/cm^2. The difference between the two is a factor of 1000 (or 25 *40). This is a direct scale to the UV-Index, which was derived by WMO in 1994. There were UVB meetings at Diableretes, Switzerland in 1994 and 1996 to agree on this.
1) The Eqivalent Center Wavelength is not simply the FWHM. The center wavelength is not the center of the FWHM.
It goes like this:
The (FEL) lamp spectral response is passed over the raw data (multiplied or divided. . This generates the SPN data. These data are indeed normalized to "1.0".
Now these data are independent of incoming spectral distrution of the monitored "sky" spectral distribution.
The derivation of ECW and EBW :
2) The Equivalent Center Wavelength and Equivalent Bandwidth are determined by the the "boxcar method" or rectangle method.
The equivalent channel bandwidth is always slighty wider when converted with the FEL calibration lamp.
The center of the resultant rectangle (EBW) is the ECW or Equivalent Center Wavelength. The latter being independent of the spectral distribution of the monitored "sky".
Also refer to Claire Wyatts book on spectrometers. Look for the 'rectangle method', etc.
How do I get the spectral response of my instrument? Is it included in the calibration file?
Yes, your cal file contains the spectral response of your instrument.
- Chapter 5 of the attached Yesdas Manager manual has some good information about the cal & sol files.
- Chapter 3 of the attached MFR manual has good information about the spectral response.
Can a UVB-1/UVA-1 be used underwater?
Yes. Although mainly used above water, the UVA-1/UVB-1 can handle shallow depths (1 m) for periods of hours to days. The instruments are sealed and have on-board desiccants. You will find that the water's surface and suspended aquatic material tends to attenuate UV-B data in strange and unpredictable ways, mainly as a function of turbidity. A TSP-700, MFR/UVMFR, or SPUV cannot be used underwater.
What are the differences between UV-A, UV-B and UV-C radiation?
UV-A radiation refers to atmospheric radiation from 320 nm-400 nm (that's 0.320-0.400 m m). UV-A is very important to photosynthesis and plant studies.
UV-B is the shortest wavelength atmospheric radiation that actually reaches the ground, and covers from 280-320 nm (that's 0.280-0.320 nm). However, it is UV-B that causes skin cancer over prolonged exposure. Due to the strong absorption of UV-B by ozone, the actual amount of UV-B reaching the ground is highly seasonal and depends on the solar zenith angle. With a high enough resolution instrument, the UV-B spectrum will be seen to be highly variable, i.e., it is characterized by spikes and troughs instead of being a smooth curve. This spectral structure of the sun's radiation arises from atomic absorption within the sun's approximately 6000° K photosphere. Instruments exist both to measure the total integrated broadband radiation (e.g. the YES UVB-1), as well as to measure radiation along narrow wavelengths (e.g. high resolution narrowband sensors like the YES UVMFR-7 or UVRSS).
UV-C is "extraterrestrial" solar radiation, and includes light with wavelengths between 100-280 nm. Thankfully for all of us living on earth, UV-C is fully absorbed by stratospheric ozone. In fact, UV-C is a major factor in the continuous creation of ozone in the upper stratosphere. UV-C is also called "hard UV" or "vacuum ultraviolet" in certain disciplines and is useful in many industrial processes and bacteriological applications.
Why do we have to measure UV radiation? Why can't we just model it?
Our UV_Calc package (which is included with each UVB-1 pyranometer we sell) uses a simple model called Green's model and does quite a good job modeling clear sky UV irradiance. However, for non-clear skies Green's model does not work well at all. In typical non-clear conditions, UV-B radiation is quite difficult to model due to its strong dependence on changing cloud conditions, aerosols and stratospheric (column) ozone levels. Since accurately modeling the dynamic and random behavior of clouds is extremely difficult, modeling the UV-B is difficult as well. Note that established atmospheric radiation modeling tools do exist for the visible and infrared spectrum (LOTRAN / MODTRAN), but most models for UV-B are quite complex and still experimental. NCAR has more information on atmospheric models at their web site: |(a href="http://www.ncar.ucar.edu/")|http://www.ncar.ucar.edu/|(/a)|.
Can I run YES instruments from batteries alone for portable operation?
Yes, for most instruments except for the TSI-880 and RSS/UVRSS-1024 systems which have internal heaters.
YES products can be setup to run on DC. Use a lead-acid type RV/marine-type deep cycle battery. YESDAS-2 (which runs the UVMFR, MFR, SDR), will keep a battery float charged while plugged into the line. But if run "barefoot" a small wire jumper needs to be added from the "B+" to the "P+" terminal. Keep in mind that depending on the model, DC current requirements can be significant. Refer to the product data sheet to determine the maximum current drain for each sensor.
If you will be making long term, remote measurements (off the AC power grid), you will need to plan how to keep the batteries charged. If you plan to back up the batteries with solar panels or a wind generator, this is possible but you will want to carefully size the system based on expected solar insolation and/or wind levels at your site. The technology for providing off-grid power tends to be well developed and often invoves a wind-diesel hybrid solution. We know of several excellent companies that can provide commercial-quality turn-key DC power systems - contact Yankee technical support for more guidance.
What is the difference between the UVA-1 and UVB-1 pyranometers?
The two instruments are identical, except that the UVA-1 pyranometer has a spectral response of 320-400 nm and features a detector that uses a phosphor system responsive to UV-A.
Yes. Each UVB-1 and UVA-1 instrument includes our UV_Calc modeling program that lets you model other action spectrums and compare the UVB-1 measurements to Green's model. UV_Calc is also sold separately.
No, one UVPS-1 power supply will run two pyranometers: each UVB-1 or UVA-1 needs 500mA@+12V ea, plus about 30mA@-12V ea. You can also use our YESDAS-2 data logger to provide DC from your AC power mains. If you are technical, you can even build your own DC supply (however, it must be an electrically quiet linear-type DC power supply, not a switching-supply).
Can the UVB-1 or UVA-1 pyranometer be used with other data loggers besides YESDAS-2?
Yes, the output for a UVB-1 or UVA-1 pyranometer is an analog 0-4Vdc signal...so any data logger than can digitize the signal in this voltage range will work. Be sure that the data logger has differential input channels. (If it does not state so, it is likely single-ended as these are less expensive to manufacture). You must use differential inputs to eliminate analog ground loops. Also, some data loggers have input range limitations that can be easily accommodated. For example, the popular Campbell Scientific model CR-10 data logger has only a maximum input range of ± 2.5Vdc. In this case you need to simply use a two-resistor voltage divider (10kW ) to step down the voltage by a factor of 50%. Finally, do not forget that you need a source of positive and negative electrically quiet DC as well, which most data loggers do not provide. A dual output DC supply, such as the UVPS-1 will also be needed.
Step 1. You need a source of +12Vdc at 1A and -12Vdc at 30 mA.
Step 2: You need something to record the analog output of the UVB-1. This output is proportional to the UV-B irradiance, and is calibrated at the factory. If you happen to have a Campbell CR-10 that only can do +/- 0-2.5v, you can use a resistive voltage divider to prescale the signal down. Of course, if you do not need a data logger, a simple handheld D.V.M. or chart recorder will also work.
If this all sounds a bit complicated, we sell a complete 32-channel data logger/ power supply system, YESDAS-2, as well as a simple UVPS power supply. Both the YESDAS-2 and UVPS-1 convert 110/220Vac to provide the +12 Vdc/-12Vdc voltages and are housed in weatherproof NEMA-4X enclosures. The YESDAS-2 supplies DC power from AC mains and logs data from up to 32 analog instruments and 6 pulse type digital instruments. YESDAS-2 is optimized for solar measurements and knows the sun's elevation angle. This is stored with each data reading and permits post angular correction of direct-normal radiometer data
Why should we choose a UVB-1 over a competitve product such as a Solar Light 501?
Yankee Environmental Systems, Eko and Solar Light broadband UV radiometers were extensively tested by NIST.
See http://nadp.nrel.colostate.edu/UVB/uvb_instruments_broadband_nist_frame.html for more information.
Vital went out of business in 1997. The BW-100 and their other broadband instruments used thin film interference filters instead of phosphors and were therefore not as stable as most UV-B users require. In contrast, in 1993, our model UVB-1 was evaluated by NIST's radiometric physics division along with other manufacturers' instruments. Based on the outcome of these NIST tests, the US government selected YES UVB-1 instruments for the UV monitoring network run by the U.S. Department of Agriculture. For more information, visit the USDA UV-B monitoring program at http://uvb.nrel.colostate.edu.
Why is data from a narrowband UV radiometer more useful than that from a broadband pyranometer?
This question could apply to most areas of the electromagnetic spectrum, but in the UV portion of the spectrum its sharp structure is essentially lost in the integrated nature of a broadband detector. Narrowband UV radiometers such as the SPUV-10, UVMFR-7 and UVRSS-1024 measure either discrete lines or the entire spectrum, respectively. This comes at a price in terms of complexity; hence the market popularity of broadband pyranometers.
The dessicant plug is not refillable. There are also two dessicant packs inside the UVB housing, so if you are having condensation, it may indicate a leak. The best solution is to send the unit to us for a calibration, and we can check the seals at the same time.However, we do sell a dessicant kit (essentially a new dessicator plug). If you would like more information on that, or to send the unit in for calibration, please email This email address is being protected from spambots. You need JavaScript enabled to view it..
The orange wire (to the heater board and heater) is isolated from the red wire within the instrument.
Join the orange wire and red wire at the supply only.
That design prevents higher current (heater current) from interacting with the amplifier (red wire +12V).
It was also designed to allow the user to disable the heater while still running the instrument.
We highly recommend against not running the heater.
Under normal (and highly recommended) operation:
In 99 % of all cases, the red wire and orange wire are fed from the same +12 V source at the users power supply (only). They are joined at the supply in the outside world only. (The black wire of course is -12 V)
So if a user 'sees' +12V on the orange wire inside his instrument, then the answer is yes - his orange wire is already attached to his red wire back at the users +12V supply in the outside world somewhere. They built their own UVPS.
+12V = orange +12V = red -12 V = black.
per the UVB manual schematic.
Can I run a TIR without power?
No. Aside from powering the ventilation system (and possibly heaters), power is required for the instrument itself. The thin film thermopile employed in the TIR-550 has higher output than many other thermopiles used in pyrgeometers and pyranometers, but it also has relatively high output impedance.Incorporating a very low offset chopper-stabilized amplifier in the instrument with high quality resistors insures a low output impedance and high output voltage. This greatly reduces the burden on the data acquisition system employed. In effect, some of the errors normally associated with the data acquisition that are not counted in the instrument are already incorporated into the TIR-550.
Do I need to correct for the dome temperature of the TIR-550?
No. One of the design goals of the TIR-550 was to eliminate the need to correct measurements for dome temperature. The small size of the silicon dome and other design factors keep the dome temperature very close to the temperature of the thermopile. Radiant heat exchange with the dome is proportional to (Tdome^4-Ttp^4); thus if the dome temperature tracks that of the thermopile, the error is eliminated.