PWS100 Present Weather Sensor Revision: 3/12 C o p y r i g h t © 2 0 0 6 - 2 0 1 2 C a m p b e l l S c i e n t i f i c , I n c .
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PWS100 Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. Introduction...............................................................1-1 2. Cautionary Statements.............................................2-1 2.1 Sensor Unit Safety ................................................................................ 2-1 2.2 Laser Safety ..............................................................
PWS100 Table of Contents 6.4 Grounding and Lightning Protection .................................................. 6-14 6.4.1 Equipment Grounding ............................................................... 6-14 6.4.2 Internal Grounding .................................................................... 6-14 6.4.3 Lightning Rod ........................................................................... 6-14 7. Operation .................................................................. 7-1 7.
PWS100 Table of Contents 7.4.1.29 Message Field 105 DSP PSU Voltage, Hood and Dew Heater % Duty ..................................................... 7-18 7.4.1.30 Message Field 106 Upper, Lower Detector Differential Voltage, Calibrated Visibility mV............................... 7-18 7.4.1.31 Message Field 150 Serial Number, Operating System and Hardware Version.................................................. 7-18 7.4.1.32 Message Field 151 Day Count, Hours, Minutes, Seconds ...........................
PWS100 Table of Contents 8.3 Additional Sensor Connections............................................................. 8-3 8.3.1 Using a CS215-PWS on the PWS100......................................... 8-4 8.3.2 Using Other Sensors on the PWS100.......................................... 8-4 8.4 PWS100 Control Unit ........................................................................... 8-5 8.5 Measurement Signal Processing ........................................................... 8-5 8.
PWS100 Table of Contents List of Figures 4-1. PWS100............................................................................................... 4-1 6-1. Effect of structure on air flow ............................................................. 6-1 6-2. Hardware for mounting the top of the DSP plate to a pole ................. 6-4 6-3. Placing the PWS100 onto the bracket ................................................. 6-5 6-4. PWS100 mounted to a mast or pole .......................................
PWS100 Table of Contents C-3. PWS100 communication cable .......................................................... C-4 C-4. Enclosure wiring details for communication cable ............................ C-4 List of Tables 7-1. Command Set ...................................................................................... 7-2 7-2. Message Field parameters.................................................................... 7-7 7-3. Assumed bulk density of various particle types. .........................
Section 1. Introduction The PWS100 is a laser-based sensor that measures precipitation and visibility by accurately determining the size and velocity of water droplets in the air. It can be used in weather stations in road, airport, and marine applications. The PWS100 uses advanced measurement techniques and algorithms to calculate individual precipitation particle type.
Section 1.
Section 2. Cautionary Statements 2.1 Sensor Unit Safety The PWS100 sensor has been checked for safety before leaving the factory and contains no internally replaceable or modifiable parts. WARNING Do not modify the PWS100 unit. Such modifications will lead to damage of the unit and could expose users to dangerous laser light levels and voltages. WARNING In unusual failure modes and environmental conditions the sensor hood could become hot.
Section 2. Cautionary Statements If the laser is operated outside of the housing then the following warning applies: INVISIBLE LASER RADIATION AVOID EXPOSURE TO BEAM CLASS 3B LASER PRODUCT WARNING 2-2 Check that the laser warning label on the sensor is still visible and can be clearly read on an annual basis. When installing the sensor avoid pointing the laser housing towards areas where binoculars are in common use.
Section 3. Initial Inspection Upon receipt of the PWS100, inspect the packaging and contents for damage. File damage claims with the shipping company.
Section 3.
Section 4. Overview The PWS100 Present Weather Sensor is a laser based sensor capable of determining precipitation and visibility parameters for automatic weather stations including road, marine and airport stations. Due to its advanced measurement technique and fuzzy logic algorithms, the PWS100 can determine each individual precipitation particle type from accurate size and velocity measurements and the structure of the received signal.
Section 4.
Section 5. Specifications 5.1 Mechanical Specifications Measuring Area: 40 cm2 (6.2 in2) Housing Materials: Iridite NCP conversion coated aluminium (RoHS compliant) and hard anodized aluminium. Outer parts also coated with marine grade paint. Weight: 8.2 kg (18 lb) excluding power supply / communications enclosure Shipping Weight: 20.4 kg (45 lb) Dimensions: 115 cm × 70 cm × 40 cm (42.3 in × 27.6 in × 15.8 in) Mountings: U-bolt mounting to mast or pole with outer diameter from 1.25 in to 2.
Section 5. Specifications 5.3 Optical Specifications 5.3.1 Laser Head Specifications Laser Source: Near-infrared (IR) diode, eye safe Class 1M unit output Peak Wavelength: 830 nm Modulation Frequency: 96 kHz Laser Head Lens Diameter: 50 mm (1.97 in) 5.3.2 Sensor Head Specifications Receivers: Photodiode with band pass filters Spectral Response: Maximum spectral sensitivity at 850 nm, 0.62 A/W (0.6 A/W at 830 nm) Sensor Head Lens Diameter: 50 mm (1.97 in) Lens Check Light Source: Near-IR LED 5.
Section 5. Specifications 5.6.2 Precipitation Measurements Particle Size*: 0.1 mm to 30 mm (0.004 in to 1.18 in) Size Accuracy*: ± 5% (for particles >0.3 mm) Particle Velocity: 0.16 ms-1 to 30 ms-1 Velocity Accuracy*: ± 5% (for particles >0.
Section 5. Specifications The particle buffer is able to hold raw data for 500 typical particles. The processor is able to process the particles at a rate of 120 particles per second, typically. This means if more than 120 particles per second fall through the sample volume of 40 cm2 the particle buffer will start to fill up. If the rain rate exceeds 120 particles per second for a prolonged period, the buffer could run out of space and particles will be lost.
Section 6. Installation 6.1 Location and Orientation The PWS100 measures environmental variables and is designed to be located in harsh weather conditions. However there are a few considerations to take into account if accurate and representative data from a site are to be obtained. NOTE The descriptions in this section are not exhaustive. Please refer to meteorological publications for further information on the locating of weather instruments.
Section 6. Installation In order to minimize user interaction with the unit, the PWS100 should be placed away from sources of contamination, in the case of roadside monitoring, larger mounting poles can be used. More regular maintenance will be required when the instrument is placed in areas where contamination is unavoidable or where measurements may be safety critical.
Section 6. Installation 6.3 Installation Procedures 6.3.1 Assembling the PWS100 The PWS100 comes as a single unit, with the DSP enclosure attached to the base of the sensor arms. The PWS100 and power/communication enclosure (if purchased) are typically mounted to a Campbell Scientific tripod. Usersupplied mounting structures should be strong enough to withstand high winds, without significant movement. See the manuals supplied with your tripod for details on how to set up ready for PWS100 mounting.
Section 6. Installation Bracket Tab U-bolt Bracket DSP Plate FIGURE 6-2.
Section 6. Installation Notches Bracket Tab FIGURE 6-3.
Section 6. Installation FIGURE 6-4. PWS100 mounted to a mast or pole CAUTION 6-6 Ensure that the PWS100 is mounted according to Figures 6-2 through 6-4. Do not reposition, once fixings are tightened, by forcing the arms of the unit as this can damage the unit.
Section 6. Installation 6.3.3 Connecting Cables The sensor unit comes with the DSP control unit fixed to the sensor arm. All cabling between the sensor heads and the DSP unit is premade. An SDI-12 sensor connection is fixed into the DSP terminal strip. The connection is terminated with a LEMO socket on the lower face of the DSP housing. This is primarily wired for the CS215-PWS but is also used with the PWC100 Calibrator.
Section 6. Installation PG9 CABLE GLAND EARTH GROUND LEMO 4-PIN (CONNECTOR FOR CS215-PWS) FIGURE 6-5.
Section 6. Installation 6.3.5 Desiccant The desiccant bags should be removed from the plastic bags in which they are shipped before placing them inside the enclosure. Two 100 g bags of desiccant are supplied with the PWS100. Desiccant use depends on your application (see below). The desiccant should be firmly strapped to the DSP cover inside the PWS electronics enclosure using the strap provided and as shown in Figure 6-6. FIGURE 6-6.
Section 6. Installation FIGURE 6-7. Removal of DSP cover. FIGURE 6-8. Exposing the DSP board.
Section 6. Installation The location of the dip switches on the board is shown in Figure 6-9 and the dip switches themselves are shown in detail in Figure 6-10. The following settings are available: PWS100 dip switch settings:0 = off; 1 = on. switch 1 slew rate 0 slow slew rate (default) 1 fast slew rate switch 2 communication mode 0 RS232 (default) 1 RS485 (note – load resistor may be required – see Section 6.3.6.1) switch 3 duplex mode 0 full duplex (default) 1 half duplex (RS485 – see Section 6.3.6.
Section 6. Installation FIGURE 6-9. DSP board dip switch location (circled) FIGURE 6-10.
Section 6. Installation 6.3.7 Installing Power Supply Power supply connections can be made in the PWS100 24 Vdc/12 Vdc power supply cabinet using the power cable supplied with the PWS100. Din rail contacts are mounted inside the power supply enclosure that allows connection to the two power supplies (see Figure 6-11). FIGURE 6-11. Labeled DIN-RAIL contacts 6.3.8 Start-Up Testing On start-up the PWS100 will run internal diagnostic tests and check the status of any connections to the instrument. 6.3.
Section 6. Installation replacing the desiccant. This is of particular importance if using the sensor in corrosive or salt laden atmospheres. 6.4 Grounding and Lightning Protection 6.4.1 Equipment Grounding The present weather sensor must be properly grounded to protect it from transients and secondary lightning discharges. The PWS100 has a ground lug on the outside of its enclosure. This ground lug is connected to a tripod’s grounding system via a 12 AWG copper wire.
Section 7. Operation 7.1 Introduction The best way of becoming familiar with the sensor is to setup the sensor and connect it to a PC running Windows and the Campbell Scientific Present Weather Viewer program. This software allows easy setup of the sensor and a graphical display of the measurements being made. It also provides an easy way of upgrading the firmware of the sensor. It is not intended to capture or store data on a permanent basis but is provided as a demonstration, test and setup tool.
Section 7. Operation configuration options. These are discussed below within the context of setting up the sensor using a terminal emulator. 7.3 Terminal Mode In normal operating mode the sensor will respond to a number of “root” commands, shown in Table 7-1. Those commands allow the configuration of the sensor in a non-interactive fashion, the polling of data and also switching the sensor into an interactive user menu mode.
Section 7. Operation In the descriptions which follow ↵ symbolizes the pressing of the ENTER key. Input parameters in italics should be user-defined characters appropriate for the command. Unless otherwise stated, all command parameters should be separated by a space. To support addressed RS-485 networks, each PWS100 can be assigned an identifier, shown as Pws_Id below. By default the PWS_Id is set to 0 (zero).
Section 7. Operation NOTE The data storage function will not store data while the terminal or menu is active. This means data will be missing during these periods. To reduce data loss reduce the amount of time that the terminal or menu are active. 7.3.3 Message Polling While the menu system or terminal mode are closed, it is possible to poll data from a suitable set sensor (see Sections 7.4.1 and 7.6.1 for information on how to set up messages for polling).
Section 7. Operation Section 7.4.6 gives further details of how to set up the PWS100 with the command set in the terminal mode (option 7 from the SETUP menu). FIGURE 7-1. PWS100 setup menu 7.4.1 Top Menu Options 0, 1 and 2 (Message n) The options 0, 1 and 2 from the SETUP menu are entitled ‘message 0’, ‘message 1’ and ‘message 2’. These are used to setup the message outputs for messages with ID 0, 1 and 2. Selecting one of these brings up the MESSAGE menu as shown in Figure 7-2.
Section 7. Operation If option 1 is chosen from the MESSAGE menu then the system will display the MESSAGE PARAMETERS and FIELDS menu for that message as shown in Figure 7-3. From here 19 fields can be filled in. Field 0 is the message interval. This is set in seconds and will be the interval between which output messages are given. Field 1 is the message mode and fields 2 to 19 are output parameters which can be user set. FIGURE 7-3.
Section 7. Operation From the MESSAGE PARAMETERS and FIELDS menu if field 1 is chosen then the MESSAGE MODE menu (see Figure 7-5) will be displayed. Here the options are to store and output to the serial port (option 1) which is useful for on screen analysis of real-time data, or store only (option 2) more useful when logging data. FIGURE 7-5. Message mode menu From the MESSAGE PARAMETERS and FIELDS menu if fields 2 to 19 are chosen then the MESSAGE FIELD menu will be displayed as shown in Figure 7-6.
Section 7. Operation TABLE 7-2. Message Field parameters Message Field 7-8 Parameter Output 34 External sensor (Aux) 40 Precipitation intensity (mmh-1) 41 Precipitation accumulation 42 Drop size distribution bin values (0.
Section 7. Operation Note that user defined messages cannot make field references to other user defined messages but can make reference to fixed messages from field 10 to 19 and all other message fields. 7.4.1.1 Message 0 (the Default Output) User message 0 can be set by setting the Message Field parameters as required using other message fields from 10 upwards. By default and after a hardware reset (see Section 6.3.10, Load Factory Defaults) or a software reset (see Section 7.9.
Section 7. Operation 7.4.1.3 Message Field 10 To 19 Fixed Messages No fixed messages have been defined yet. The user cannot change the fixed messages. 7.4.1.4 Message Field 20 Visibility Range (m) This field will output the average visibility range (m) calculated over the Message_Interval defined. 7.4.1.5 Message Field 21 Present Weather Code (WMO) This field will output the Present Weather Code (WMO) calculated over the Message_Interval defined. 7.4.1.
Section 7. Operation 10. DC voltage of upper detector greater than 1.5 V. This can be caused by sun directly shining into lens or a pws fault. 11. DC voltage of lower detector greater than 1.5 V. This can be caused by sun directly shining into lens or a pws fault. 12. Particle processor is unable to process all particles due to limited time and buffer resources. Particles are missed and data could be inaccurate.
Section 7. Operation NOTE The PWS100 only measures particles / visibility 90% of the time so precipitation intensity is scaled appropriately. 7.4.1.15 Message Field 41 Precipitation Accumulation This field will output the precipitation accumulation (mm) calculated over the Message_Interval defined. NOTE The PWS100 only measures particles / visibility 90% of the time so precipitation totals are scaled appropriately. 7.4.1.
Section 7. Operation 15 16 17 18 19 20 =>4.50 =>5.00 =>5.50 =>6.00 =>6.50 =>7.00 0.50 0.50 0.50 0.50 0.50 93.00 Class 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Particle speed class Speed [m/s] =>0.0 =>0.2 =>0.4 =>0.6 =>0.8 =>1.0 =>1.4 =>1.8 =>2.2 =>2.6 =>3.0 =>3.4 =>4.2 =>5.0 =>5.8 =>6.6 =>7.4 =>8.2 =>9.0 =>10.0 Class width [m/s] 0.2 0.2 0.2 0.2 0.2 0.4 0.4 0.4 0.4 0.4 0.4 0.8 0.8 0.8 0.8 0.8 0.8 0.8 1.0 90.0 7.4.1.
Section 7. Operation 7 0.795 0.13 8 0.925 0.13 9 1.055 0.13 10 1.185 0.13 11 1.375 0.25 12 1.625 0.25 13 1.875 0.25 14 2.125 0.25 15 2.375 0.25 16 2.750 0.50 17 3.250 0.50 18 3.750 0.50 19 4.250 0.50 20 4.750 0.50 21 5.500 1.00 22 6.500 1.00 23 7.500 1.00 24 8.500 1.00 25 9.500 1.00 26 11.000 2.00 27 13.000 2.00 28 15.000 2.00 29 17.000 2.00 30 19.000 2.00 31 21.500 3.00 32 =>23.000 77.
Section 7. Operation 10 0.95 0.1 11 1.10 0.2 12 1.30 0.2 13 1.50 0.2 14 1.70 0.2 15 1.90 0.2 16 2.20 0.4 17 2.60 0.4 18 3.00 0.4 19 3.40 0.4 20 3.80 0.4 21 4.40 0.8 22 5.20 0.8 23 6.00 0.8 24 6.80 0.8 25 7.60 0.8 26 8.80 1.6 27 10.40 1.6 28 12.00 1.6 29 13.60 1.6 30 15.20 1.6 31 17.60 3.2 32 =>19.20 80.8 7.4.1.
Section 7. Operation 8 =>0.70 0.1 9 =>0.80 0.1 10 =>0.90 0.1 11 =>1.00 0.2 12 =>1.20 0.2 13 =>1.40 0.2 14 =>1.60 0.2 15 =>1.80 0.2 16 =>2.00 0.4 17 =>2.40 0.4 18 =>2.80 0.4 19 =>3.20 0.4 20 =>3.60 0.4 21 =>4.00 0.8 22 =>4.80 0.8 23 =>5.60 0.8 24 =>6.40 0.8 25 =>7.20 0.8 26 =>8.00 1.6 27 =>9.60 1.6 28 =>11.20 1.6 29 =>12.80 1.6 30 =>14.40 1.6 31 =>16.00 3.2 32 =>19.20 3.2 33 =>22.40 3.2 34 =>25.60 74.
Section 7. Operation 11 =>1.00 0.2 12 =>1.20 0.2 13 =>1.40 0.2 14 =>1.60 0.2 15 =>1.80 0.2 16 =>2.00 0.4 17 =>2.40 0.4 18 =>2.80 0.4 19 =>3.20 0.4 20 =>3.60 0.4 21 =>4.00 0.8 22 =>4.80 0.8 23 =>5.60 0.8 24 =>6.40 0.8 25 =>7.20 0.8 26 =>8.00 1.6 27 =>9.60 1.6 28 =>11.20 1.6 29 =>12.80 1.6 30 =>14.40 1.6 31 =>16.00 3.2 32 =>19.20 3.2 33 =>22.40 3.2 34 =>25.60 74.4 7.4.1.
Section 7. Operation 7.4.1.24 Message Field 100 Upper, Lower LED temperature This field will output the sampled internal upper and lower LED temperatures (°C). 7.4.1.25 Message Field 101 Upper, Lower Detector Temperature This field will output the sampled internal upper and lower detector temperatures (°C). 7.4.1.
Section 7. Operation 7.4.1.35 Message Field 154 Watchdog Count, Maximum Particles Per Second, Particles Not Processed, Time Lag This field will output a watchdog count which indicates the number of resets of the system due to error, the maximum number of particles stripped per second over the measurement interval, the number of particles stripped in real time but not processed and a time lag in seconds indicating how far behind processing has got at some point during the measurement interval. 7.4.1.
Section 7. Operation FIGURE 7-6. Message field menu Choosing option 0 on the MESSAGE FIELD menu will display more output parameter options. Choosing option 999 will delete the field (note that subsequent fields already selected shift up to fill the gap in the fields). Choosing option 1000 + field number will insert the chosen parameter in the field selected and shift subsequent filled fields down one field. Also available on the MESSAGE menu is the option to delete the message (option 2).
Section 7. Operation FIGURE 7-7. Delete message menu 7.4.2 Top Menu Option 3 (Set Time and Date) Choosing option 3 from the SETUP menu brings up the TIME AND DATE menu (see Figure 7-8). On this menu it is possible to set the time and / or date for the PWS100. To change the time alone enter it as hh:mm:ss, for example 16:30:00. To change the date alone enter it as yyyy/mm/dd), for example 2007/02/04.
Section 7. Operation 7.4.3 Top Menu Option 4 (Configuration) Choosing option 4 from the SETUP menu brings up the CONFIGURATION menu (see Figure 7-9). From this menu the basic configuration of the sensor is set. FIGURE 7-9. Configuration menu Option 1 of the configuration menu gives the PWS100 ID menu (Figure 7-10). Here a PWS100 ID can be set. This is effectively the station address which is required on any communication with the PWS100.
Section 7. Operation FIGURE 7-10. PWS100 ID menu Option 2 of the configuration menu gives the TRH PROBE TYPE menu (see Figure 7-11). Choose the correct temperature / relative humidity probe that is connected to the PWS100 from the list given. FIGURE 7-11. TRH probe menu Selecting probe type 2 configures the sensor to expect a temperature and humidity reading to be sent to it from a remote system using the RSENSOR command.
Section 7. Operation Option 3 of the configuration menu gives the WETNESS PROBE TYPE menu (see Figure 7-12). Choose the correct wetness probe that is connected to the PWS100 from the list given. FIGURE 7-12. Wetness probe menu Option 4 of the configuration menu gives the AUX PROBE TYPE menu (see Figure 7-13). Choose the correct auxiliary probe that is connected to the PWS100 from the list given. FIGURE 7-13.
Section 7. Operation Option 5 of the configuration menu gives the HOOD HEATER TEMPERATURE menu (see Figure 7-14). The value that is to be set needs to be between 0° and 50°C. The hood temperature is maintained by the system at the value set. FIGURE 7-14. Hood heater temperature menu Option 6 of the configuration menu gives the DEW HEATER MODE menu (see Figure 7-15). The dew heaters can be set to on, off or auto. Auto mode turns the heaters on, except when main hood heaters are set to heat. FIGURE 7-15.
Section 7. Operation Option 7 of the configuration menu gives the OUTPUT MODE menu (Figure 7-16). This refers to the use of packetized output. The message framing is done by STX (ASCII character 02) and ETX (ASCII character 03); these act as start and end delimiters. The default value is 1 (STX / ETX on). These framing characters are useful for programmers writing code to pick up data coming from a sensor outputting data asynchronously to the device collecting it. FIGURE 7-16.
Section 7. Operation FIGURE 7-17. Calibration warning screen Once confirm is typed followed by the return key, the CALIBRATION top menu (see Figure 7-18) appears. The options available to the user are: 0 to view and enter the calibration disc constants, and 1 to view and adjust the PWS100 calibration. FIGURE 7-18. Calibration top menu Selecting option 0 on the CALIBRATION top menu will bring up the CALIBRATION DISC CONSTANTS menu (see Figure 7-19).
Section 7. Operation FIGURE 7-19. Calibration disc constants menu Selecting option 1 on the CALIBRATION top menu will bring up the VIEW / ADJUST CALIBRATION menu (see Figure 7-20). On this menu the latest calibration values will be evident in the left hand column of values headed latest. Selecting option 0 on the VIEW / ADJUST CALIBRATION menu will return the user to the previous menu without invoking any calibration changes.
Section 7. Operation FIGURE 7-20. View / adjust calibration menu Option 9 of the configuration menu gives the TERMINAL MODE menu (see Figure 7-21). Choose whether CRC16-CCITT checksum verification is required. NOTE When terminal mode is set to 1 all terminal commands need a CRC. For example “open 0;d2d5” a semi-colon is used to indicate start of CRC in 4 byte ASCII hex. The CRC is calculated either from the start of new line or after a [STX] up to but not including the semicolon.
Section 7. Operation Option 10 of the configuration menu gives the PSU SHUT DOWN VOLTAGE menu (Figure 7-22). Enter the PSU input voltage level below which the PWS100 will enter low power mode. Enter `0.0’ to disable this feature (default). FIGURE 7-22. PSU shut down voltage menu NOTE This feature is usually used to protect batteries from deep discharge. There is a hysteresis of 0.9V applied.
Section 7. Operation 7.4.5 Top Menu Option 6 (Weather and Alarm Parameters) Choosing option 6 from the SETUP menu brings up the WEATHER AND ALARM PARAMETERS menu (see Figure 7-24). This menu allows for the setup of the visibility range alarms, snow water content factor and the mixed precipitation thresholds. FIGURE 7-24. Weather parameters menu There are three visibility alarms, each of which is set separately by selecting 1, 2, or 3, followed by enter on the WEATHER PARAMETERS menu.
Section 7. Operation The snow water content scaling factor (SWCF) can be adjusted by choosing option 4 on the WEATHER PARAMETERS menu. This will bring up a line asking for a value. Depending on atmospheric conditions likely to be encountered, a wide range of snow water content figures can be observed dependant on the bulk density of the particle. Particle bulk density depends on the structure of the particle (e.g.
Section 7. Operation FIGURE 7-26. Snow water content adjustment The mixed precipitation threshold value can be adjusted by choosing options 58 on the WEATHER PARAMETERS menu. This will bring up a line asking for a value between 0 to 1. A value of 0 means there is no threshold for mixed precipitation – a single other type of particle in a specific event will give rise to a mixed event, therefore mixed events are highly likely; and may easily be caused by the occasional erroneous particle classification.
Section 7. Operation FIGURE 7-27. Mixed precipitation threshold adjustment 7.4.6 Top Menu Option 7 (Terminal) Choosing option 7 from the SETUP menu brings up the TERMINAL screen (see Figure 7-28). Pressing any key brings up the terminal as described in Section 7.3. FIGURE 7-28. Terminal active screen 7.4.7 Top Menu Option 8 (Info) Choosing option 8 from the SETUP menu brings up the INFORMATION menu (see Figure 7-29). This shows various parameters for the PWS100 system.
Section 7. Operation of the operating system or a hardware reset. The SDI-12 values of temperature and relative humidity will be -999.00 if no such information is available such as when no probe is connected to the SDI-12 port. The diagnostic mode shows two values. The first value is the flag for the fuzzy diagnostic mode (0 or 1); see Section 7.5.2, Retrieving Historical Data for more information.
Section 7. Operation FIGURE 7-30. Done menu 7.5 Message Related Commands Messages can be set for a variety of output types, including fixed standard types and user defined types. The system can be set up to send automated messages at user defined intervals, or can be used as a user polled system. 7.5.1 Automatic and Polled Message Sending While the command mode is closed, the PWS100 will operate by sending data output as set by the user in either automatic or polled modes (see Section 7.3.
Section 7. Operation The Message_Interval parameter must also be defined from 0 second to 32767 seconds which is the rate at which the system will display the output message and the period which statistics are calculated over (the factory and reset default for ID 0 is 60 seconds). If the Message_Interval is 0 then it will set the message polling mode (see Section 7.3.3, Message Polling for a description of the manual data polling command).
Section 7. Operation To set manual polling mode the MSET command should be of the form: MSET Message_ID 0 0 Message_Fields ↵ e.g., MSET 0 0 0 105 106↵ NOTE A minimum message interval of 10 seconds can be set for all types of message field output. If a time is set less than 10 seconds some output parameters may not function correctly. 7.5.2 Retrieving Historical Data Historical data can be output by using the HDATA period command. Parameter period is the number of seconds to output going back in history.
Section 7.
Section 7. Operation 7.5.3 Viewing Data Output on the Command Line A number of records (defined by the number n) of uncollected historic m data (message data) can be output to the command line in ASCII text format in exactly the same format as defined in the messages. To do this type: HMDATA n ↵ If the parameter n is omitted then all uncollected data is output.
Section 7. Operation To set the adjustable visibility limit parameters, type: SETPARAM vislim1 vislim2 vislim3 snowwater mixthreshold↵ The system will respond by displaying the new settings as described above with SETPARAM↵ command. Please see Section 7.4.5 for a description of the thresholds. TABLE 7-4. Weather parameters. Parameter Function VISLIM1 Set a visibility alarm below which a particular alarm will be given. VISLIM2 Set a visibility alarm below which a particular alarm will be given.
Section 7.
Section 7. Operation Currently three other sensors can be connected to the PWS100. The sensor configured is changed by parameters TRH_Sensor (Temperature and RH%), Wetness_Sensor and Aux_Sensor. Section 8 gives further details of how to connect optional sensors. Table 7-5 gives the IDs of various sensors. To add these to the system put the appropriate sensor ID to the appropriate sensor parameter. TABLE 7-5. Detectable sensors.
Section 7. Operation Select the Xmodem 1k protocol and select the OS file using the ‘Browse’ button. Once selected press the ‘Send’ button. The Xmodem file send dialog box then opens displaying download progress and will close automatically once the download has completed. The OS can be seen to be being installed by a series of memory block erasures, followed by writing of the OS and verification of the OS. The user is then prompted to wait for 5 seconds for the OS to restart. The new OS is now installed.
Section 7. Operation 7.8.3 Running the Calibration The detection volume is calibrated using the PWC100 calibrator. The calibration fixture plate which holds the calibration unit is mounted in place on the top of the sensor boss. The PWC100 calibrator runs automatically when the start button is pressed and will provide values for the PWS calibration as shown in Section 7.4.3 and Figure 7-20. Normally, the PWC100 calibrator is only used as a check device in the field.
Section 7. Operation To set the time without the date being altered the following should be used: TIME hh:mm:ss↵ 7.9.2 Resetting the System The system is reset by using the RESET command as follows: RESET↵ This will terminate all current measurements and reset the system. The time, date and calibration values will be maintained, but all other user enterable data are lost and will need to be input again as required. If a problem is found with the sensor first try power cycling the sensor.
Section 7. Operation relative gains or losses of the two clocks that the logger will over time either receive an extra transmission from the sensor or not get a transmission from the sensor in a given period. Apart from accepting this as being inevitable the only solution to this is to get the sensor to output more frequently than you need the logger to receive data and have the logging system work with the latest transmission, but this is not always ideal or possible.
Section 7.
Section 7.
Section 7.
Section 8. Functional Description 8.1 General The PWS100 Present Weather Sensor is an optical sensor using the best of scatter meter and disdrometer techniques to give accurate analysis of weather conditions including precipitation classification, precipitation intensity, drop size distributions and visibility range. Visibility is measured using the forward scatter technique, which gives an estimation of the meteorological optical range (MOR).
Section 8. Functional Description FIGURE 8-1. Laser unit Rod lens Doublet lens Cylindrical lens Grating Laser FIGURE 8-2. Laser unit showing light sheet production (not to scale) The sensor units as shown in Figure 8-3, comprise a lens, a filter tuned to the wavelength of the laser output and a photodiode placed at the back focal length of the lens with suitable amplification electronics.
Section 8. Functional Description FIGURE 8-3. Sensor unit Filter Plano-convex lens Photodiode FIGURE 8-4. Sensor unit showing light path extents (not to scale) 8.3 Additional Sensor Connections Although it is possible to use the PWS100 as a stand alone present weather sensor, its ability to distinguish particle types is improved when certain other sensors are connected to the unit.
Section 8. Functional Description 8.3.1 Using a CS215-PWS on the PWS100 The CS215-PWS temperature and RH probe should be connected directly to one of the free SDI-12 connectors at the base of the DSP enclosure as shown in Figure 6-5. The CS215 is mounted inside a radiation shield and needs to be mounted away from the actual detection volume of the PWS100 in order to avoid any turbulence effects in the volume that could give rise to inaccuracies in the measurement of speed and size of particles.
Section 8. Functional Description 8.4 PWS100 Control Unit The PWS100 control unit, shown in Figure 8-5 as a block diagram, is a custom designed DSP board comprising a DSP, memory, timing circuits and analogue to digital converter. FIGURE 8-5. Block diagram of PWS100 control unit The DSP board controls all of the functions of the system, including switching of heaters when the temperature sensors in each head pass certain thresholds, laser modulation, signal analysis and communications.
Section 8. Functional Description 8.6 Algorithm Description 8.6.1 Detecting and Classifying Precipitation The PWS100 has a structured detection volume consisting of four sheets of light each 0.4 mm in depth with 0.4 mm spacing. The area of detection is approximately 40 cm2 as defined by the overlap of the two detectors each of which is 20° off of the light sheet propagation axis. Detection of precipitation is carried out in real-time.
Section 8. Functional Description Signal to Pedestal Ratio Analysis 100 600 Snowflakes 90 Snow Grains 500 Drizzle 80 70 400 60 50 300 40 200 30 Particle Count (Liquid) Particle Count (Snow) Rain 20 100 10 0 0 1 1.5 2 2.5 3 3.5 4 4.5 5 Signal to Pedestal Ratio FIGURE 8-6. Signal to pedestal ratio values for different precipitation types. The above data was collected during the sensor development. Results from production instruments will differ.
Section 8. Functional Description size/velocity value of 0 for drizzle, 0.4 for rain, 0.3 for snow flakes, 0.4 for graupel, 0.1 for ice pellet etc. The fuzzy value assigned is always between 0 and 1. Since certain particle types are mutually exclusive then some types will be assigned 0 based on pure logic (e.g., a particle > 0.5 mm diameter will have a rain value that can be >0 whereas the drizzle value for this type will always be 0).
Section 8. Functional Description The PWS100 has exceptional sensitivity to the start and end of precipitation events. NOTE To avoid falsely reporting precipitation due to insects etc., the sensor will not report the detection of particles at the start of an event until a threshold of ~3 particles per minute is exceeded. Measurements of both intensity and accumulation are however subject to some assumptions as is common with most optical rain detectors.
Section 8. Functional Description 8.6.3 Precipitation Accumulation Precipitation accumulation is calculated in millimeters over a specified time period by summing the volume of all precipitation particles falling through the defined volume. As mentioned above, as with most other similar optical detectors, the PWS100 will be subjected to increased error and bias in windy conditions. Accumulations of snow are based on the water content of those particles.
Section 8. Functional Description 8.6.4.2 Visibility Types Also by using the WMO SYNOP code table (4680) a visibility type can be defined. These types cover mist, fog, haze and smoke. See Appendix A for details. 8.6.4.3 Weather Classes Continuous and showers or intermittent classes can be defined when analyzing the time series of code output given by the PWS100 over a given time period. These are again given specific codes in the WMO 4680 table.
Section 8. Functional Description possible to measure the immediate surroundings, selecting appropriate parameters, which can be related to the environmental air quality and human visual perception. The PWS100 has the ability to define an obscurant type and determine a visibility value based on the amount of particle scatter calibrated against the type of particles in the detection volume.
Section 8. Functional Description 8.8 Internal Monitoring The PWS100 has a number of internal checks including temperature analysis inside each head unit of the sensor, temperature check at the laser, dirty window contamination checks and voltage monitoring (particularly for the laser source). These can be selected for output with the weather data; see Section 7.4 for details.
Section 8.
Section 9. Maintenance 9.1 General The PWS100 Present Weather Sensor is a robust instrument that will provide years of uninterrupted weather monitoring. Calibration of the instrument is carried out at the factory and can be redone easily on site with the optional calibration kit or carried out by Campbell Scientific if required. Only general cleaning of the lenses is required to keep the sensor working efficiently. 9.
Section 9. Maintenance It is advisable to use airduster to blow any loose dust and dirt from the lenses as a first step. Using a lint free lens cloth or lens tissue impregnated with a small amount of isopropyl alcohol solvent, clean the lens surface by dragging the cloth across the lens surface being careful not to apply excessive pressure. Excessive pressure may lead to some types of contaminant scratching the lens surface. Over time such scratches can lead to reduced sensor accuracy.
Section 10. Troubleshooting 10.1 Introduction If your PWS100 seems to be operating incorrectly, there are a number of checks you can make to isolate the problem. These checks may enable you to solve the problem or at least provide vital basic information for one of our engineers should you need to contact Campbell Scientific. 10.2 Possible Problems The following problems can be encountered. Following the steps laid out should enable you to resolve these problems quickly and easily. 10.2.
Section 10. Troubleshooting 10.2.3 Ice has formed in the end of the hoods The heaters may not be working. Enter the command mode of the sensor, run DIAGSET with the following command: DIAGSET 10 102 Ensure that the laser hood temperature (first value following the 9000 and 0 output) is above zero. If it is not then it is possible that the heaters may not be active or may need servicing. To check the settings of the hood heaters use the SETCONFIG command.
Section 10. Troubleshooting checked that there are no spider’s webs on the instrument, especially in and around the detection volume and hoods of the unit. If spider’s webs are present they should be removed as they can collect condensed water vapor to form droplets on the strands which may give rise to spurious signals. Secondly flying insects may cause spurious signals; however these are likely to be disregarded by the instrument and are unlikely to lead to classification of precipitation.
Section 10.
Appendix A. PWS100 Output Codes The codes that are used in the PWS100 are taken from WMO Manual on Codes 1995 edition, Suppl. No. 5 (VIII.2005), Rec. 5 (CBS-XIII). Table A-1 shows the weather types available as output from the PWS100. Codes in italics are not implemented. Codes in bold are extensions of the WMO 4680 table to allow single Metar code output for different output combinations.
Appendix A.
Appendix A.
Appendix A. PWS100 Output Codes Freezing precipitation, slight or moderate2 47 -UP / UP P- / P P- / P i<5.34 - Freezing precipitation, slight 47 -UP P- P- i<1.34 - Freezing precipitation, moderate 47 UP P P 1.3≤i<5.34 - Freezing precipitation, heavy 48 +UP P+ P+ i≥5.34 - Reserved 49 - - - - - DRIZZLE 50 DZ L L No Limit ≤0.5 mm Drizzle, not freezing, slight 51 -DZ L- L- i<0.1 ≤0.5 mm Drizzle, not freezing, moderate 52 DZ L L 0.1≤i<0.5 ≤0.
Appendix A. PWS100 Output Codes Rain and snow, light 67 -SNRA P- SR- i<1.84 - 4 - Drizzle and snow, light 67 -SNDZ P- SL- i<0.6 Rain, drizzle and snow, light 67 -SNRADZ P- SRL- i<1.24 - Rain (or drizzle) and snow, moderate or heavy2 68 SNRA / +SNRA / SNDZ / +SNDZ P / P+ SR / SR+ / SL / SL+ - - Rain and snow, moderate 68 SNRA P SR 1.8≤i<7.54 - Rain and snow, heavy 68 +SNRA P+ SR+ i≥7.54 - Drizzle and snow, moderate 68 SNDZ P SL 0.6≤i<2.
Appendix A. PWS100 Output Codes Snow showers, moderate1 86 SHSN S S 1.0≤i<5.0 >0.5 mm Snow showers, heavy1 87 +SHSN S+ S+ i≥5.0 >0.5 mm Reserved 88 - - - - - Showers of hail, with or without rain or rain and snow mixed, not associated with thunder1, 5 89 SHGR A A No Limit >0.
Appendix A. PWS100 Output Codes Subjective Observations (Trappes, Paris, France, 14-16 May 1997) and the Working Group on Surface Measurements (Geneva, Switzerland, 27-31 August 2001). TABLE A-2. Light, moderate and heavy precipitation defined with respect to type of precipitation and to intensity, i, with intensity values based on a three-minute measurement period. Variable Drizzle Range i < 0.1 mm h-1 0.1 ≤ i < 0.5 mm h-1 i ≥ 0.5 mm h-1 Intensity class Light Moderate Heavy Rain (also showers) i < 2.
Appendix A. PWS100 Output Codes However it is also noted that non-mixed reports such as rain or snow may also contain a proportion of other types of particle such as drizzle which is not included in any intensity range modification for non-mixed reports.
Appendix A. PWS100 Output Codes TABLE A-6. Intensity bounds for rain, drizzle and snow. Rain Light Moderate Heavy Drizzle Snow i<2.5 i<0.1 i<1.0 2.5≤i<10.0 0.1≤i<0.5 1.0≤i<5.0 i≥10.0 i≥0.5 i≥5.0 Rain, Drizzle and Snow i<1/3×2.5+1/3×0.1+1/3×1.0 i<1.2 mmh-1 1/3×2.5+1/3×0.1+1/3×1.0≤i<1/3×10+1/3×0.5+1/3×5.0 1.2 mmh-1≤i<5.17 mmh-1 i≥1/3×10+1/3×0.5+1/3×5.0 i≥5.17 mmh-1 TABLE A-7. Intensity bounds for rain, drizzle, ice pellets, hail and snow.
Appendix A.
Appendix B. Wiring EARTH GROUND FIGURE B-1. Underside of DSP enclosure TABLE B-1.
Appendix B. Wiring FIGURE B-2.
Appendix C. Cable Selection C.1 Power Cable The PWS100 is provided pre-wired with a default 10 m power cable as shown in Figure C-1. This cable should be grounded using the cable screen at both ends. One end is to be connected to the power sources for the DSP (12V) and hood heaters (24V) the other is fed through the cable gland on the base of the PWS100 DSP enclosure and fixed in the DSP terminal strip as shown in Figure C-2.
Appendix C. Cable Selection WIRING INSTRUCTIONS COLOR SCREEN BLACK RED +24 Vdc – GREEN -24 Vdc – WHITE DSP G G 12V POWER A/C OR DC A/C OR DC FIGURE C-1. PWS100 power cable FIGURE C-2.
Appendix C. Cable Selection C.2 Communication Cable The PWS100 has RS-232, RS-422 and RS-485 communications capability. Use a screened 2 × 0.22 mm2 twisted pair cable. Maximum length is 15 m for RS-232, 300 m for RS-422 and 300 m for RS-485. The PWS100 is provided pre-wired with a default 10 m communications cable as shown in Figure C-3 (other lengths available on request) which is terminated at one end with a 9 pin D-connector (DB9).
Appendix C. Cable Selection WIRING INSTRUCTIONS DSP COLOR 9WAY TX-Z CTS-Y RTS-B RX-A G G485 G BLUE YELLOW WHITE GREEN BLACK RED SCREEN 2 8 7 3 5 N/C CASE FIGURE C-3. PWS100 communication cable FIGURE C-4.
Appendix D.
Appendix D.
Appendix D.
Appendix D.
Appendix D.
Appendix D.
Appendix E.
Appendix E.
Appendix E. Menu System Map Menu operation 1..Menu will activate when terminal is open 2..Return only will go to previous menu 3..Incorrect entry will return to same menu 4..Delete will clear current entry 5..
Appendix E.
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