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Operational TSI-440 Frequently Asked Questions

FAQ Legend:All Products
Product Class (Sky Imaging)
This Product (TSI-440)

3. Operational

1. Can the TSI detect thin cirrus clouds?

A TSI instrument can distinguish between high thin cirrus and thick cloud cover, but there is an inherent limit to what the TSI determines to be thin vs. what is thick or what is clear (just as with human observers). The main difference is that the TSI is consistent, while human observers are generally not. So the TSI software filters the image into just two categories clear and cloud. A user-adjustable threshold permits you to separate the two categories by setting the point at which the TSI determines that a cloud qualifies as "a cloud."

2. Does the TSI require periodic calibration?

NO. However, as the mirror ages you will need to replace it. A short demos showing how to do this is located at:


This is a MPEG video/audio 1 minute clip that explains how to replace the mirror. Your browser or media player should load this automatically and play it, and you need speakers and an audio card to hear the audio.

3. What is the maintenance required for a TSI-440 or TSI-880? Is there an annual maintenance fee?

TSI systems come with a 1 year warranty and are designed for continuous duty exposure. About once every other week it is helpful to wipe the mirror with a soft cloth and glass cleaner such as Windex. The frequency depends on the amount of pollen in the air, but is not critical.

Waxing the mirror every couple of months is mandatory. The closer to the ocean the site is, the more likely the mirror will corrode over time. However, this is a field replaceable part and there is a short MPEG video at: <AHREF="http://www.yesinc.com/products/demos/tsimpeg/tsi-mirror-replacement.mpg"</A>

This MPEG video/audio clip that explains how to replace the mirror. Your browser or media player should load this automatically and play it, and you need speakers and an audio card to hear the audio.

On the TSI-880 the internal UPS battery will require replacement every 5 years. The TSI-440 requries that you supply a car battery.

There is also a surge suppressor on the Ethernet but we recommend that you use fiber optic isolation to protect your LAN - even though the TSI has a ground wire to the case, a direct lightning hit might hurt the Ethernet hub on your LAN. With fiber optics this isn't a problem.

Our policy on long term maintenance contracts is 10% of the current instrument price per year and covers all problems, including lightning hits.

4. Is there a heater/cooler in the TSI system?

There is a large, AC line-powered, thermostatically-controlled heater under the mirror to keep moisture off it. The electronics inside the NEMA enclosure also tend to keep it dry inside. There is no system cooler.

5. What sort of CCD is used - is it for video motion or still picture?

The CCD imager used is a still frame camera, and not a low cost NTSC / PAL type motion video camera. The maximum practical sampling (frame) rate is two frames a minute, about 1/1000th as fast as the 30 frames/second of a video camera. The CCD used offers much better low light performance and better spatial sampling compared to a consumer-type video camera. A slower frame rate permits longer CCD integration times and also allows higher color stability, critical to getting good cloud detection performance. As clouds do not move very fast, using video would be a waste of bandwidth.

6. How does the CCD deal with the sun saturating and washing out the CCD?

Both the TSI-880 and TSI-440 have an automated rotating shadow mask driven by an ephemeris CPU control system with absolute-encoder. If ever frozen in place by rime ice, the heaters will eventually melt the ice, and the absolute encoder will resume tracking.

7. Does the CCD use Red/Green/Blue filters to get false colors? What is 24 bit color?

No, there is no moving filter as would be required on a monochrome CCD. The imager used is a 24 bit color CCD. This means for each pixel, three separate bytes each represent Red, Green and Blue. So 8+8+8=24 bits.

8. What is the raw TSI image file format?

Output is in industry standard formats: raw images are JPEG, and the processed output images of cloud cover are in "portable network graphics" (PNG).

9. What is the spatial resolution of images from a TSI imager?

The TSI output image resolution is fixed. While the raw JPEG pictures are in a rectangular format, the usable data comes from the round, active area of the mirror which has an effective resolution of approximately 260 x 260 pixels.

10. Can the TSI indicate cloud base distance?

The TSI detects the percent of cloud but like the Cyclops it has no depth perception. We have considered the R&D of multi-TSI systems for stereoscopic viewing of clouds (at least two TSI systems would be needed for such an application). However, while an interesting problem, we feel that conventional ceilometers are more cost-effective for this application.

11. Can the TSI software be fine-tuned in terms of sensitivity? On the animated TSI demo that I downloaded, I noticed that some thin clouds don't get recognized, which would pertain to high altitude cirrus clouds as well. Can the user adjust the sensitivity of cloud detection or are there any other parameters that can be changed?

Yes, you can adjust the threshold to permit a seasonal or site-specific micro-climate bias. You can also adjust how many degrees elevation (up from the horizon) gets processed, which we call the horizon cutoff. Tempered against this idea is that most people ultimately crave a sort of standard algorithm. That reduces the risk of "apples vs. oranges" comparisons.

12. How much bandwidth is required by the TSI-440 and TSI-880 assuming one minute sampling rate?

Network bandwidth required for both the TSI-440 and TSI-880 is about 30Kbytes/minute.

13. Does the TSI software take into consideration the curvature of the sky and calculate cloud cover appropriately?

NO. All pixels are weighted equally.

14. Is the TSI software compatible across multiple software platforms?

On the TSI-880 the only software required is a Java-enabled browser.

On the TSI-440 the processing of images can take place on a Windows 9x/NT/2000/XP PC. Image processing can take place either in real time ("on line") or later ("off line"). The TSI-440's Ethernet interface communicates to a remotely located PC running the software.

For remote sites we recommend using the TSI-880.

15. On the built-in Ethernet connection, what type of connectors are provided (e.g. BNC 10Base2 or RJ-45 for 10BaseT)?

RJ-45 10BaseT on the TSI-440 and RJ-45 10/100BaseT on the TSI-880. It is not necessary to have a local PC at the site once you have initialized the rotating mirror electronics. A local PC is only required to process and store images if you want a local display. Generally, on the TSI-440 you'll want to run TSI Manager on a remote machine that is safe and warm via TCP/IP and the Internet. However, you can also have a local PC at the site to store images from a TSI-440. This PC will need to be equipped with a 10-BaseT NIC adapter. The TSI contains its own 4-port RJ45 hub. One of the RJ45 ports is switchable as an uplink port - so you can direct wire it to your hub, while a PC are also connected.

16. We also own your UVB-1 pyranometer. Could you explain any benefits of obtaining the TSI working in conjunction with it.

Clouds affect UV to a high degree. There has been interest in trying to estimate UV from % cloud cover, but at the moment this is an academic area of research. In principle, it should be possible to directly correlate the two measurements, enhancing confidence in the measurements.

17. How do fixed items in the TSI field-of-view (e.g. towers) affect processed data?

Because these objects show up as "permanent clouds", it is best to site the instrument with the best clear view as possible. In practice, the size of fixed objects in the picture vs. processing errors always represent engineering tradeoffs.

18. What are white horizontal lines across a TSI raw image?

This should not occur during normal operation. If it does, you should cover the CCD immediately until you fix the shadowband alignment problem. White horizontal lines indicate that the camera is being exposed to excessive light, that is, the blocking band is out of alignment allowing direct sunlight to get to the CCD. It generally indicates improper alignment, band settings, improper time or latitude/longitude settings. This can be verified remotely on the TSI-440 by initiating the Check Alignment feature on TSI Manager, or the setup tab on the TSI-880.

19. How often must the shading strap be replaced on the TSI mirror? Is a spare needed?

The TSI shadowband is a black strip of tape. It should last several years before needing replacement. You can get this locally or from YES. At very remote sites you can leave a rolled up strip of tape tucked inside the electronics enclosure. If you avoid using strong cleaners on the mirror the tape should last a long time.

20. Does the TSI-440 have the ability to have its clock automatically updated from an outside source (for instance, via communication with our system) to keep the time stamp coordinated with the rest of our instrumentation?

No--on the TSI-440, the processing PC actually sets the time stamp on all image files so its time must be accurately maintained. Unfortunately, since motherboard clocks on PCs tend to not have good long term stability, we strongly recommend that you have the PC that runs the TSI software synchronized to NIST time via the Internet via NTP. See http://www.nist.gov for free software to do this. (However, the TSI-880 can stay synchronized to NIST as long as an active Internet connection is available.)

21. Do we have to run the heater on the TSI all the time? It seems to need a lot of power.

YES. Because of the potential for condensation, you must run the heater to prevent corrosion. The heater keeps moisture dew, rain, ice and snow off the mirror and out of the NEMA electronics enclosure. The heater is thermostatically controlled, meaning that if the air temperature is higher than the set point, no power is drawn. If power consumption is an issue you can wire the heater to a separate, potentially less reliable AC feed. On the TSI-440 the actual DC power requirement is less than 1.5 amps at 12 VDC (18 watts) without the heater. The heater, when it is on, is in the neighborhood of 500 watts, so it is the dominant power sink. Keep in mind that computer will draw a significant amount of power as well.

22. How important is time keeping on the TSI?

The TSI-880 supports automated synchronization of the time clock to an internet time services such as NIST's atomic clock.

On the TSI-440, time must be accurate to about one minute to keep the shadowband tracking properly. There are actually two clocks to worry about: one on the mirror that calculates the ephemeris, and a second on the PC that sets the image's time stamp. The clock on the mirror control system is quite stable, and the width of the blocking strap makes it not such a big deal if the mirror time drifts a few minutes or so. If you check the clock every month or two on the TSI itself this is adequate. If your PC is networked to the internet, a task that can be automated is setting the clock on your PC via a shareware program available from http://www.nist.gov.

23. Can I operate the TSI with the mirror removed, even for a short time?

No. Do not remove the mirror with the power applied to the system. The heaters are designed to keep ice and snow off the mirror and if the mirror is removed there will be no convective coupling of heated air to the thermostat and the heaters will become very hot quickly. Under no circumstance should the heaters be turned on when the mirror is removed.

24. Do birds seem to bother the TSI mirror?

Not usually. While we have observed that birds do not seem to like sitting on the TSI, periodic cleaning is a good idea. If your site is in an area with a strong bird population, you may want to add some sharp prongs on top of the TSI imager to prevent birds from landing and blocking the image, or dirtying the mirror just to be on the safe side. These can be purchased at major building material supply vendors.

25. Does TSI stop collecting data down during the nighttime?

YES. Data are not stored at night, but power remains on to keep moisture off the system. However, you can adjust how low the sun elevation has to be before data acquisition stops. Also, you can adjust the minimum solar zenith angle for processing cloud cover data. This is important because as the sun gets low the images get too dark to resolve the color differences. You can take data down to the horizon, although the image processing worsens as the images get darker.

26. Does the TSI calculate percentage of sky coverage and output an actual number, or is some programming involved?

TSI software converts raw color sky images into a cloud fraction "processed" file. A separate optional SQL database package for the TSI-880 called YESDAQ permits connection to existing data collection networks.

27. How long can the TSI be operated unattended?

As long as power is maintained to the instrument, and the mirror kept free of dirt, deposits, or bird debris, the TSI can be operated unattended indefinitely. The networking connection between a TSI-440 and the PC acquiring and processing the images is a key reliability issue. You also need to think about AC power quality from a system-level point of view. On the TSI-880 an integral UPS keeps the system running during brief outages and shuts the system down in an orderly fashion if power is lost for more than a few minutes. The TSI-880 image processing system is self-contained and up to 720 images are locally buffered until the connection is restored and data collection via YESDAQ resumes. On the TSI-440, if the network connection is lost data is lost

28. Why when I point IE to the TSI-880 do I get a "unable to connect to TSI server" message.

If you can see the URL of the TSI-880 but you get this error message, you either have a TCP/IP connectivity problem, or potentially you are running the Sun Java Virtual Machine (JVM) in IE.

Microsoft (who makes Internet Explorer - IE) and Sun (who controls Java) are now producing incompatible versions of Java. Java runs in what is called the Java Virtual Machine (JVM). Newer versions of Windows are letting you choose which JVM you want to run, Sun's or Microsoft's. Some web sites require that Sun's Java is required to view them, and if you have installed the Sun JVM plugin to view it, it sets up by default, IE use the Sun JVM.

If you view the URL of a TSI-880 and get a "unable to connect to TSI server" dialog box, and the System Docto" checks the system and returns all "OK's", go to your MS-Windows control panel and using the Sun JVM icon, tell the Sun Java Virtual Machine control not to use Internet Explorer. Once this is changed, restart the browser and the TSI-880 should display properly.

Note that some web browsers such as Mozilla and Safari may need an updated JVM to display the TSI-880 data correctly.

29. 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.

30. Can I get spectroradiometric information from a TSI image?

Spectroradiometers always give results in terms of power-per-unit-area-per-unit-wavelength. The CCD images have colors and intensities that are relative due to auto-brightness that adapts to sky conditions and thus pixels cannot be calibrated or temperature-corrected.



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