atmos:535:projects:joss-waldvogel_disdrometer
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+ | ====== Joss-Waldvogel Disdrometer ====== | ||
+ | * Manafacturer: | ||
+ | * Model Number: RD-80 | ||
+ | --- //[[|Brad Klotz]] 2006/09/24 15:43// | ||
+ | |||
+ | |||
+ | {{atmos: | ||
+ | |||
+ | ===== Description ===== | ||
+ | |||
+ | ==== Cost ==== | ||
+ | * __**Purchase**__: | ||
+ | * Sensor: ~ $5,000.00 | ||
+ | * Processor: ~ $7,000.00 | ||
+ | |||
+ | * __**Maintenance/ | ||
+ | |||
+ | * __**Calibration**__: | ||
+ | |||
+ | ==== Measurement Physics ==== | ||
+ | **General Setup:** | ||
+ | |||
+ | |||
+ | * The disdrometer contains two units: the sensor, which gets exposed to rain drops and the processor, which is used for analog processing and digitizing of the signal sent from the sensor. These two units are connected by a 20 meter cable, which allows for the processor to be stored inside. | ||
+ | |||
+ | |||
+ | **Summary of Process:** | ||
+ | |||
+ | |||
+ | * The disdrometer takes the vertical momentum of a drop hitting the surface of the top of the rubber membrane and converts it into an electric pulse with amplitude as a function of drop diameter. Analyzing the pulse height will give different size distributions of the rain drops. | ||
+ | |||
+ | |||
+ | **Specific Instrument Description: | ||
+ | |||
+ | |||
+ | * The amplitude of the electric pulse is also proportional to the mechanical momentum of the drop. The sensor transforms this momentum into the electric pulse. | ||
+ | |||
+ | |||
+ | * The sensing unit contains two main parts, which are a feed-back amplifier and an electromechanical part. A styrofoam | ||
+ | |||
+ | |||
+ | * The processor helps get rid of undesired signals, due to noise, to lower the 90 dB dynamic range of the sensor signal and to help transform it into seven bit code through digitization. | ||
+ | |||
+ | |||
+ | * A schematic drawing shows all the different parts associated with retreiving and processing the information. | ||
+ | |||
+ | {{atmos: | ||
+ | |||
+ | ==== Performance Characteristics ==== | ||
+ | |||
+ | |||
+ | * Below is a diagram of the traditional setup: | ||
+ | |||
+ | {{atmos: | ||
+ | |||
+ | |||
+ | * Performace Specifications: | ||
+ | |||
+ | {{atmos: | ||
+ | |||
+ | ==== Field Projects ==== | ||
+ | |||
+ | ** TI1 Building site, College Station, TX ** | ||
+ | |||
+ | * Site developed and maintained by Texas A&M University | ||
+ | |||
+ | * The J-W Disdrometer was placed and maintained at this site under the supervision of Dr. Courtney Schumacher, who also took the photographs shown below. | ||
+ | |||
+ | * Two more J-W Disdrometers are currently being installed in Houston, TX and Galveston, TX. | ||
+ | |||
+ | * Local rain rates were calculated from the data that was recorded by the disdrometer. | ||
+ | |||
+ | |||
+ | * //Below are a couple of pictures of the field site:// | ||
+ | |||
+ | {{atmos: | ||
+ | {{atmos: | ||
+ | |||
+ | * //Here is an image of the data display platform:// | ||
+ | |||
+ | {{atmos: | ||
+ | |||
+ | * //And here are some figures of some data that was taken by Karen Brugman at the field site in College Station on September 9, 2006. The figures were created by me from the data that Karen collected.// | ||
+ | |||
+ | {{atmos: | ||
+ | {{atmos: | ||
+ | |||
+ | ==== Documentation ==== | ||
+ | |||
+ | Here is a link to the [[http:// | ||
+ | |||
+ | ==== Reference ==== | ||
+ | |||
+ | http:// | ||
+ | |||
+ | |||
+ | Lawrence D. Carey, Ph.D. - Assistant Professor, Texas A&M University | ||
+ | |||
+ | Courtney Schumacher, Ph.D. - Assistant Professor, Texas A&M University | ||
+ | |||
+ | |||
+ | |||
+ | ===== Calibration ===== | ||
+ | |||
+ | === Method === | ||
+ | There are a couple of ways to calibrate the disdrometer, | ||
+ | |||
+ | **Disdrometer Sensor:** | ||
+ | * When using drops of approximately 0.8mm diameter at near terminal velocity, v< | ||
+ | |||
+ | **Disdrometer Processor: | ||
+ | * The processor’s job is to reduce the dynamic range of the sensor so that the data can be processed by the analyzer. | ||
+ | |||
+ | ==== Sources of Error ==== | ||
+ | |||
+ | * Location of the drop has an effect on the amplitude that is measured. | ||
+ | |||
+ | |||
+ | * Since the calibration is performed in the lab with known drop sizes, very large drops can produce some errors. | ||
+ | |||
+ | |||
+ | * Physical wear on the instrument from being exposed to water can eventually cause errors, but these are not large errors. | ||
+ | |||
+ | |||
+ | * When used in an outdoor setting, other elements of the weather can effect the flight of a raindrop, causing situations like the drop hitting the edge of the sensor. | ||
+ | |||
+ | ==== Exposure Requirements ==== | ||
+ | |||
+ | * In order for the disdrometer to get the best data, it must be exposed to precipitation such that the wind and/or other elements do not play a large role in how the drops hit the sensor. | ||
+ | |||
+ | |||
+ | * This instrument is designed for outdoor use and can therefore be left outside as long as desired. | ||
+ | |||
+ | ===== Deployment ===== | ||
+ | |||
+ | ==== Measurement Methods ==== | ||
+ | |||
+ | * The versatility of this instrument is good since it can be used for different purposes. | ||
+ | |||
+ | * The main use, though, is for meteorological applications that produce some kind of signal on the disdrometer. | ||
+ | |||
+ | * However, there is still one main measurement method, and that was explained above in the **// | ||
+ | |||
+ | ==== Deployment Platforms ==== | ||
+ | |||
+ | * The disdrometer can be deployed in pretty much any environment, | ||
+ | |||
+ | * This disdrometer can be used to determine the following: | ||
+ | - Use of determining drop size in radar applications | ||
+ | - Precipitation physics, such as rain rate | ||
+ | - Microwave physics, due to the accoustic nature of the instrument | ||
+ | - Soil erosion | ||
+ | |||
+ | * From the list of applications, | ||
+ | - Near a radar to combine data from reflectivity values and drop sizes | ||
+ | - Any place where precipiation would be easy to record | ||
+ | - Locations near a microwave emitting source, probably another instrument | ||
+ | |||
+ | ==== Communication ==== | ||
+ | |||
+ | * The sensor cable communicates with the processor by transferring the pulse signal so it can be converted and digitized. | ||
+ | |||
+ | |||
+ | * The processor communicates with the personal computer through an RS-232 connection, which allows for the digitized information to be read by the provided software program. | ||
+ | |||
+ | |||
+ | * One note about the sensor cable is that if a longer cable is desired, the sensitivity will be decreased. | ||
+ | |||
+ | * Although it would be nice to have simultaneous communication with more than one instrument, this instrument does not have this type of versatility. | ||
+ | |||
+ | ==== Power and Installation ==== | ||
+ | |||
+ | * It is important to take precautions when installing the disdrometer. | ||
+ | |||
+ | * The list of power requirements appears in the table above, but there is a provided power cord that works with a standard 115V AC outlet. | ||
+ | |||
+ | ===== Data ===== | ||
+ | |||
+ | ==== Quality Control ==== | ||
+ | |||
+ | * There are several ways to ensure the quality of the data: | ||
+ | |||
+ | - Measurements are made continuously throughout an event and new information is stored in the ' | ||
+ | - UPS power also helps so that data will not be lost | ||
+ | - Screensavers interrupt the acquisition of data and should not be used | ||
+ | |||
+ | |||
+ | ==== Quality Assurance ==== | ||
+ | |||
+ | * Assurance of the data is important, so the following are very helpful with ensuring the quality assurance: | ||
+ | |||
+ | - DISDRODATA, the provided software, should be used for all analysis and acquisition because if other software programs are used, the amount of data that can be viewed would be reduced | ||
+ | - Using other software programs also creates a less stable environment, | ||
+ | - Since all disdrometers have been precalibrated in a lab, this should provide some assurance. |