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Operational SPUV-6/10 Frequently Asked Questions

FAQ Legend:All Products
Product Class (Rotating Shadowband Radiometers)
This Product (SPUV-6/10)

3. Operational

1. If the performance of a MFR, UVMFR, or SPUV head is changed due to a repair or engineering change order, can I have the head characterized "before and after" the change?

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.

2. For many months the shadowband shaded the diffuser correctly, but getting closer to the summer solstice, we notice it does not appear to have enough length to shadow the diffuser completely. Each day the gap of shadow becomes slightly larger.

This is happening near summer solstice it is not adjusted correctly. This will crete significant, non-correctable measurement errors to direct-and-diffuse around solar noon. Here are some things to try to get it aligned:

1. 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.

2. 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.

3. Use a bubble level to verify 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.

4. 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.

For further help, our free tech support is now provided on line:

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3. How are MFRs/RSSs calibrated?

Each MFR is characterized yearly in our optical calibration facility, in five ways:

1. A North/South angular scan (via a cosine bench),

2. An East/West angular scan ( " ),

3. Relative spectral filter function response (via a monochromator),

Channel dark levels, and

4. Absolute voltage response (via a NIST traceable irradiance standard lamp).

The actual MFR head characterization takes four steps:

1 & 2. 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.

3. 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"

4. 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.

4. 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".

5. 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.

6. I want to set up a UVB-1, MFR, UVMFR, or SPUV site and only download data every few days on my YESDAS-2. Is unattended operation doable? What about the TSI and RSS?

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.

7. What is the ambient temperature operating range of the radiometers (UVB-1, MFR/UVMFR and SPUV? Will they work in the arctic?

YES has successfully deployed MFR and SPUV systems running from the tropics to Point Barrow, Alaska. However, above 75 north or south latitude you won't be able to make direct-normal or diffuse measurements (a SPUV works just fine above this range but requires a tracker). The SPUV working temperature range is -50 to +50 ; the MFRs working temperature range is -35 C to +40 C. But extreme wind loads can decrease the range slightly. If you can protect the instrument from wind and add additional infrared heaters for cold operations it can work at much lower temperature ranges, as the MFR Point Barrow installation indicates.

8. How long does it take for the memory in a YESDAS-2 datalogger to fill up?

A basic YESDAS-2 has 32Kb of built in memory, but most YESDAS systems are sold with memory card (PCMCIA) options. With the standard size 32Kb buffer, assuming an MFR-7 is connected and taking 15 second samples, the 32Kb buffer would fill up in approximately 30 hours. YESDAS Manager contains a built-in "projected memory usage calculator."

With a 1 MB memory card, a MFR-7 with YESDAS-2 can retrieve data for 40 days assuming sampling every 15 seconds and averaging four samples together before storing, i.e., one-minute storage intervals. It also assumes there are 12 hours of daylight at the site. A YESDAS-2 logs data during the daytime only. So, if there are fewer daylight hours at the site, say 10 hours, then the card would fill up in 48 days; if there are more daylight hours, you'll have less time before it fills up. Also keep in mind that the MFR uses seven channels, and takes three measurements on each (direct-normal, diffuse, total), so 21 data points are stored for each sample. Most instruments typically require just one channel per measurement.

 

 

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This page was last updated on Monday, September 11, 2006 .