Mintaka - Starpath School of Navigation
Contents
1. Duo mounted on a Duo connected to a power pack common desktop in a waterproof box The pres display easel sure release allows the unit to work properly when sealed Starpath Corporation 3050 NW 63rd St Seattle WA 98107 1 206 783 1414 helpdesk starpath com starpath com barometers2. buttons step forward or backward through the displays 20 2 2 Show Graph Graph Tendency 3 Show Values Graph Pressure Tendency Code Show Crap eA Graph Tendency maa raph Tendency d Set up Main Menu Show Graph Graph Tendency Pressure tendency is internationally defined as the change in pressure over the past 3 hours It is usually expressed in mb hPa It can be used to anticipate changes in the pressure and in some cases change in the weather as discussed in Sec 1 1 The graph shows how the tendency is changing with time The history range and display options are the same as in the pressure graphs Sec 2 1 This graph shows how the change is changing which can be a valuable aid to forecasting A steady pressure drop meaning a flat curve of tendency vs time can be a definite warning Sec 1 1 but a downward slope to this graph means the rate of pressure drop is increasing with time A fast rising pressure can also portend strong wind in some weather patterns 1 2 6 29 13 18 29 45 H DN 15N 10N SH O A 20H 15H M 7 GH Pressure tendency graph and digital readout at the cursor Note that if the elevation of the instrument changes the recorded tenden cy will reflect how the pressure changed over the last 3 hours but this will not reflect actual changes in atmospheric pressure The instrument must remain at a constant elevation for at least 3 hours for this number to be a measure
3. 61 as 10 1e 10 os os os 78 Teo 25 z4 23 22 22 21 183 3s 32 31 30 29 ze ma Moo 3s 3s 3s 34 32 31 274 50 A7 Menu Map Br2Brd3 12 22 13 Pressure we E 40177 Page 10 Station Pressure show Values 741514 UTC 7 Show Graph Log Pressure Block 15 20 30 Set up P1514 22 28 58 UTC tatoo aaa I tatata DTA D i CON MENU 2 Graph Tendency Page 16 Tendency Code 2 cl MEMES es Graph Pressure ea raph Tendency Set up Tendency Code i Graph Pressure Graph Tendency endency Code Show Values PE Show Graph Set up Show Values PME Show Graph Log Pressure bm Timeu TC EXT 01 2013 223316 LIK Cancel d Lossed 1817 4 J re23r14 2149159 1 heer re 6 00 08 1011 3 4 48 66 1016 8 5 Log Now View Entries nits Timezone Sea Level Pres Station Pres Adj System Units Timezone Sea Level Pres Station Pres Adj System Units Timezone Sea Level Pres Station Pres Ad System Units Timezone Sea Level Pres Station Pres Ad Please Confirm Clear Loa Entries Pressure MM Elevation Feet Time 24hr UTE 7 OK Cancel CET ie Ation Offset 00 000 Cancel Sensor 1016 56 D SS a 0 00 Toread 015 57 JK Cancel in Contrast Mintaka Duo versioni Woltage 4 85 Build 3366 PABAFFOEC Mounting and transport options DAO SFFQM e SELECT EXIT
4. Increasing then decreasing e N 29 3 MENU LOG PRESSURE Show Values Show Graph og Pressurejf Set up Main Menu Log Pressure The Log Pressure is another unique Duo function that is directed toward users who care to compare their observations with the official forecasts or for observers who must report pressures at the official times For many pressure applications in navigation and general weather monitor ing on shore it is convenient to compare your measured pressure with official forecasts and weather maps These official data are collected analyzed and then reported worldwide at the synoptic times of 00 06 12 and 18 UTC To facilitate these comparisons the Duo automatically records these pres sures and stores them These data are stored in UTC so it does not matter what time zone zone description you have stored in the system so long as the time is set correctly to any time zone It may also be convenient to record the pressure at specific times to document a reading corresponding to other logged events that use the pressure value such as logbook entries on vessels at sea or at specific times of laboratory measure ments on land This can be accomplished with the Log Now feature discussed below 3 1 Log Pressure Log Now This selection records the present time and date pressure and pressure ten dency in the log A manual entry is marked by an asterisk to distinguish it from the automatically
5. The Mintaka Duo barometer requires no regular maintenance The case can be cleaned with a damp cloth and mild soap Periodic calibration certification if required is available from Starpath Cor poration as well as other approved facilities Calibration is discussed in section A6 of the Appendix 5 4 Limited Warranty The Mintaka Duo is warranted to be free of defects in materials and con struction for a period of 1 year from date of initial purchase Liability is limited to repair or replacement of defective item Warranty and Registration forms are included in the package 5 5 FCC and CE Compliance This product complies with pertinent FCC and European CE requirements 38 5 6 Specifications Summary Dimensions 3 8 x 3 6 x 1 3 97 mm x 91 mm x 33 mm Power 9V to 30V DC at 12 5V 60 mA light on 37 mA light off 5V via mini USB 106 mA light on 65 mA light off DC barrel connector 5 5 mm OD 2 1 mm ID center pin positive Operating pressure range 500 to 1080 mb Operating elevation 18 000 ft 5 500 m above sea level to 1 800 ft 550 m below sea level Accuracy 1 mb over full pressure range at 20C to 50C Long term drift lt 1 0 mb year at 20C to 50C 5 7 Support Options and References For latest news and tech support tips see starpath com barometers You can also send email to helpdesk starpath com or call 206 783 1414 A general reference on many topics of barometer usage is The Barometer Handb
6. long term battery so it will keep accurate time even if the power to the barome ter is removed 1 3 Show Values History Show Values Pressure Show Graph Clock Log Pressure Set up Main Menu Show Values History Stored pressure data can be displayed graphically or in tabular format Show Values History presents a tabular list of times pressures and tendencies that shows all pressures stored Show Values History in 6 hr steps mb and inches This is a sample of the pressures stored at 6 hr intervals Use the buttons to page through the list The numbers on the right are the tendencies at these times Use the SELECT to change the time steps in this display Press SELECT to see the following window Count 85 entries Count 750 entries Timestep IE Timestep UK Cancel UK Cancel Changing History step size Now use the buttons to change the time step then press SELECT to see the new list The number of entries stored is also shown This sample must have been running for just 510 hr 6 x 85 as the file can hold 750 data points Two presses of the key brings up the option to view the data in 48 min steps In this case the 48 min file is full at 750 entries Once full new ones are added at the beginning as old ones are removed at the end The Duo stores past pressures in 11 data files according to the time steps shown in Table 1 3 15 File ID graph display graph display update inte
7. then that can be done in the Set up Units Time Zone screen without affecting the accuracy of the clock time All pressures are stored in terms of UTC so changing the time zone will not affect the pressure records it will just change the hour associated with each pressure that is displayed However the UTC used is based on the clock time and date that you set into the system with this option If you change the time or date after collecting data for some period of time the data history will start from the new time entered which would cause the time information of earlier data to be inconsistent On new set ups it would be best to reset the pressure history when resetting the time by any significant amount This does not apply to changing time zones only 29 One procedure that might help achieve best accuracy when setting a new time is to set the time on this screen ahead 20 seconds or so highlight the OK region and then when the reference time reads 1 second before your set time press SELECT The Duo clock should maintain high accuracy over a long period of time and serve as a valuable time reference for other applications Set up System Reset There are two Reset options Toggle between them with the buttons UK Cancel Two reset options Reset Pressure History This removes all records of pressure history including the Log of synoptic pressures and those manually entered into that list and all tendency da
8. wpc ncep noaa gov show isobars of accurate pressure updated every 3 hours The isobar spacing is 4 mb so reasonably good pressures can be obtained by in terpolation These maps also show station model reports for more specific values at selected locations Near a lighthouse airport or participating weather buoy you can get hourly data from the National Data Buoy Center NDBC www ndbc noaa gov When making a SLP setting on the Duo it is best to use SLP values for times close to the time you are setting it Broadcast or published values are usually for the most recent whole hour but they could be 20 or 30 minutes late in updating For example at 9 15 the most recent pressure could be for 8 00 Many stations on line such as those at the NDBC and other NWS outlets also report the pressure tendency so a time correction could be applied For example Suppose it is 0900 when you want to set the barometer and the nearest source of accurate SLP you have is 1014 8 mb valid at 0800 with a pressure tendency of 2 1 mb First recall that pressure tendency is always the net change over the past 3 hours so the tendency reported means 2 1mb 3h or the pressure is dropping at a rate of 0 7 mb hr So at 0900 you would set the instru ment to 1014 8 0 7 mb 1014 1 An especially convenient and accurate source of local sea level pressure worldwide is available at starpath com barometers This free service displays the 10 closest stations to your
9. Show Values History file and in the Show Graph Pressure plots Up to 25 manually entered pressures are allowed 4 MENU SET UP Set up options are ones that are not changed frequently Settings you select here are not changed when you Reset Pressure History Sec 4 4 but they are returned to the default values when you select Reset To Factory Settings 4 1 Set up Units Time Zone Show Values PUE Show Graph Sea Level Pres L og Pressure Station Pres Adj Samy S System MP lili CT Set up Units Time Zone This menu is used to set units for pressure and elevation as well as changing the time zone and time display mode 12h or 24h system The default values are mb same as hPa feet and Time Zone 0 corresponding to UTC same as GMT shown using a 24h system NICHE Pressure ME Sea Level Pres Elevation Feet Station Pres Ad Time 24hr UTC 7 System OK Cancel Main Set up menu 225 Use the buttons to change the options for the highlighted section and then press SELECT to move on to the next option When done press SELECT when the OK is highlighted The internal clock time itself can be adjusted as needed in the Set up System Time display The units options include mb inHg mmHg inH2O cmH20 kPa hPa 4 2 Set up Sea Level Pressure SLP Units Timezone Sea Level Pres Station Pres Adj System There are two ways to set the Duo to display Sea Level P
10. a menu page either before or after you change them with the buttons Pressing the SELECT button then either activates the choice you have made or it moves you to the next choice that must be made on that menu screen Menus with multiple options will then have a Cancel or OK option Highlight your choice and press Select to execute your selections Ihe EXIT button can be used to move from option to option without making any selection 1 MENU SHOW VALUES 1 1 Show Values Pressure Show Values Show Graph Log Pressure Set up History Main Menu Show Values Pressure This leads to the default display which shows the date time pressure along with the pressure units and mode of the pressure display station pressure or sea level pressure SLP 11 B4o 14 12 22 13 6 28 13 12 22 44 1017 7 gt 30 05 gt Station Pressure mb Station Pressure InHa Show Values Pressure mb and inches The pressure values can be displayed in several different units which can be changed at any time without affecting the recorded pressure history The default units are millibars which are the same as hectoPascals See Sec 4 1 on setting units Arrows indicating recent pressure trends are also shown starting after one full hour of operation The time and date are displayed using the time zone entered in the Set up menu The unit can also be set to display Sea Level Pressure Sec 4 2 Pressure Trend Arrows After
11. adjusting the instrument to display SLP Other applications of accurate atmospheric pressure do not care at all about SLP They care only about the actual pressure right at the location of the instru ment which is the station pressure If you are for example tuning an engine or calibrating a medical instrument in a hospital or setting controls on a sensi tive air conditioner or documenting life raft leak rates or setting controls on a regional power station it is the actual value of the pressure at the test site that matters The weather causing it and changes introduced by instrument elevation above sea level do not matter Station pressure applications require no special settings If you have reason to change the internal calibration factor for the sensors you can make an adjust ment that will change the station pressure reading All instruments that read barometric pressure either mechanical aneroid devices or electronic devices in any price range will eventually drift off of their initial calibration to some extent For the most precise work it is recommended by the World Meteorological Organization W MO and the National Weather Service NWS to check the cal ibration at least once a year Accuracy drift and calibration options are discussed later in the Users Guide How to Use this User s Guide It is recommended that you skim through the full Users Guide before using the instrument Then for details on a specific functio
12. i ees 28 par YU Ss lo Ex a x r o o o r o e x vo o o x o e e o x x o o o vo SII xl ih amp SIS o o o HIHI NN N al 9 9 9 l K K o ues nd NN ha fa at alo a fa aa ale Seco SINI NJN Slol SISiolo O al slo 1 N N o SS A O eu ih Lil la ll a a al 3 5 8 8 8 ou l o O nm Y La O E o Put Fu o O Put mg i oa E Ja lt C H LO ST o 2 c c o O E lt x o G ko DI T NIMIF OH OINIH H O r N QIFIO O NIH O O r NN PM N ulo o o ol o o ololo 00 00 0 O FIRIRIN IP oloo O i0 0 F OINI O Al Wm o FA badi lagda Laal paba kaa kata ld lab naa ling hey cu kea Ip baa la kas kea ba Dc kpa Api kaa da kanta baa e Do a Ka al s kas Es SA Al wt ow SA li FT ew eor wem wr Pew A Em ll ll A rs vmm orm os ewm mi KO O IS Bal A ed RO E oo st st to 5 9 1 0 tjene ejajn EYES a TST SIN P uo fjajafajajoja a ol a t0 o N ol x wvo o o vo l en e O J JOJ O O O O O O O O O O O Ol O O i i le lwlceolsziwIi9 5 Cu oc dor dor d cr d cr O dot do ot dot ft ot Poo Plo I Erb O O O ovi O a LS r LO Siri jajafajo enojno noja DI lo O O O O O O O O O O O l O ODIFIFITFINIOMOIN l9 7 7N NW UA d9 ig Nd GC JA es i i leN eal ea e eale o o o o olele x ixixlioj oj 9 oo PIS ojo o o o o lo o o lo lo olo lo olo
13. integrate with the Duo Valid values for data Type are h print out the available dataTypes available el print the event log in JSON format see the DEV command 35 ma print various machine attributes fs print out file status information This is a machine readable version of the file information printed by the i command Sample output of the dm ma command is Title MintakaDuo version 1 0 CurrentTime 7 15 14 10 29 19 Build 3345 SerialNumber DAOOFFQG Timezone 7 Started 7 15 14 16 49 16 RunningFor 0 40 03 DP dump pressure Command format dp mm dd yy hh mm ss Print the pressure recorded at the specified date and time If no date and time is provided the current pressure is printed DPR dump raw pressure Command format dpr Prints the pressure and temperature directly from the pressure sensors No correction of any kind is performed and no averaging of the readings are done FL invoke the firmware loader Command format fl Enters the firmware loader so a new version of firmware can be loaded into the Duos flash memory H print help Command format h Prints out help information on available commands I info Command format I Prints information on the current state of the Duo including current date and time how long the barometer has been running the files stored current units LE log pre
14. lo ololo lololo lolol lo lg Ti O e e o e sx x sri io io o rm r o w eo o x mo x o o v LO Ojojojoijo joijo jo ijo ijo jo ijo jo o o ai bal Kai kal kal ka kal kal ksa T 46 will eventually drift to some extent in calibration The WMO recommends that all barometers being used for official weather reports be checked and recalibrated as needed at least once a year You can check your device with the several methods listed for obtaining accurate pressure readings in Section A4 These must in turn be corrected for elevation as explained in Section A5 Then if you do detect that an offset to the station pressure is needed the procedure for entering it is given in Section 4 3 It is recommended to make several comparisons at various pressures over some period of time before concluding an offset is needed Even the official reference barometers cited in broadcasts can show some variation and any un certainty in instrument elevation causes a pressure of shift of 0 44 mb per 12 ft Also extremes in outside air temperature can influence the comparison of QNH station pressure corrected for elevation with QFF sea level pressure as reported by the weather service discussed in Appendix A2 For the most accurate comparison the observed station pressure should be corrected for the outdoor air temperature The data in Table A1 can be used to approximate this correction For example if your Duo barometer is located at an elev
15. mean low water MLW and mean high water MHW The correction in this case would be the same removal barometer to waterline plus a MSL correction given by MSL correction Tide MHW MWH MLW 2 Examples Removal 5 ft MLW 2 ft MHW 10 ft Then if tide 13 ft then MSL correction is 13 10 10 2 2 7 Mean seal level is 7 ft below the surface and full correction is 5 7 12 ft If tide 0 MSL correction 0 10 4 6 Mean sea level is 6 ft above the surface so the total correction is 5 6 1ft AG Calibration Procedures The Duo should maintain its specified station pressure accuracy within the long term drift specifications listed in Section 5 5 If your application requires a regular calibration certificate independent of those specifications the instrument can be returned to Starpath in Seattle for NIST traceable re certification Contact starpath helpdesk com or 206 783 1414 If you do not require a certified document you can check and adjust the instrument yourself if there is any indication that it is needed All barometers both the highest quality aneroid mechanical devices or the best electronic devices 44 e E e co Eie la Splis N e e ol s uw o wl e wo wvolejoljloljw el vljolw wl o sx r ojvolw e Es o o ore A aja a i ie od ton io 2 aula l ae abae e s ed sc bel bi E bsc sd ecd R gt olo ejej r CD CO LO LO co P alo tinlo s SIS ees i i
16. of atmo spheric pressure changes A glance at the pressure graph itself usually clarifies unusual influences on the indicated pressures and tendencies 2 3 Show Graph Tendency Code This is a unique function of the Duo designed to assist weather observers who must report not only the pressure tendency but also the official Tendency Characteristic Code that describes the nature of the change such as Decreasing then Steady Without this custom aid the Code must be determined from the shape of the past 3 hr barograph trace using a sometimes complex set of criteria This characteristic is valuable for all weather watchers not just the profes sionals as it adds more understanding to the numerical value of the pressure ten dency itself as well as extending the interpretation of reports shown on weather maps Show Values n show Graphi Gra ph Tendency Log Pressure endency Code Example of the Pressure Tendency Characteristic Code display On the left we see that the tendency at the present time is 0 8 pressure rose 0 8 mb over the last 3 hours and the shape of the trace is Code 3 in this case meaning decreasing then increasing On the right the button has been pressed to interrogate the trace at earlier times in this case showing that at time 2236 a little over 30 min ago the pressure was 1019 0 and the tendency was 0 70 The Code at that time was 1 reflecting a different shape to the 3 hr period pre
17. of the information command 33 eooo i CoolTerm_0 7 E New Open Save Connect Disconnect Clear Data Options View Hex Help IMintaka Duo Recording Barometer build 3216 serial number DAQQ FFQE 2 22 14 9 13 23 UTC 6 Started 2 19 14 9 13 12 UTC 6 running for 3 d 80 00 11 samples collected 6130 Sample files Id Collection Interval Size Samples Last Entry UTC 6 0 00 15 r30 r30 2f22 14 9 13 15 01 30 750 750 2 22 14 03 00 750 750 2 22 14 06 00 750 750 2 22 14 12 00 12 00 750 750 2 22 14 9 12 00 9 12 00 9 9 9 24 00 750 750 2 22 14 9 12 00 9 6 6 6 8 12 00 48 00 750 750 2 22 14 12 00 00 00 750 488 2 22 14 6 00 00 00 00 750 167 2 22 14 00 00 750 150 2 22 14 110 1d 0 00 00 750 PS 2 21 14 1 Used 74 of file storage Barometer State hourUnits 24 timeZone UTC 6 pressureUnits mb elevationUnits Feet barometerCorrectionType Elevation show running avg 1 elevation 0 0 offset 0 00 verbose No samples per second 18 0 contrast 75 supply voltage 4 96 Led Off running average 24 baurdrate 57600 Sensor Manager Calibrated pressure no elevation correction 1016 8 diff 0 4 filter Averaging Sensor temp 90 0 filtered pressure 1016 9 raw 1016 9 Sensor 1 temp 89 6 filtered pressure 1016 6 raw 1016 6 oo difference temp 4 pressure 0 35 00 00 00 00 00 00 A Ch Un UJ PJ I NaN G GGG aag usbserial DADOFFOF 57600 8 N 1 m ets G DTR DCD Connected 00 00 29 o 0 9 cs G
18. one hour of operation the arrows shown to the right of the pressure value is a graphic indicator of how the pressure is changing to provide a quick visual notice of significant changes The definitions used to determine which arrows are displayed are consistent with those used by the World Meteorologi cal Organization WMO The numerical value of the change over the past 3 hr is called the Pressure Tendency After a full 3 hours of operation the tendency values are stored with each recorded pressure The numerical values can be plot ted as a graph or shown in a digital list of the data in the Show Values History option The pressure trend arrows however indicate the rate of change on a more timely basis After 1 hour of operation the anticipated 3 hr change will be indi cated by these arrows and this value will then be updated every 15 seconds Thus these arrows are a quick visual description of the rate of pressure change which can be checked more specifically by referring to the graph display or the official pressure tendency display which is calculated strictly on the difference between present pressure and the pressure 3 hours earlier There are various factors that can cause the pressure to change with time especially on a moving vessel but a good rule of thumb is any pressure changing Fast can be a valuable sign of a pending change in the weather Often by the time the change is Very Fast the weather has already notably change
19. other smaller factors that contribute to the QNH to QFF conversion These corrections become increasingly more uncertain with increasing elevation above 1000 ft 300 m The Table A1 corrections however will always improve your value of SLP for comparison with official reports The temperature corrections should be applied to any barometer calibration that is done by comparing your observed station pressure with official reports of SLP The free online barometer calibration service at starpath com barometers offers a way to take into account the air temperature factor 48 Ship s Barometer Corrections Table A2 includes the barometer corrections needed to convert a station pres sure reading at elevation to the equivalent sea level pressure taking into account instrument elevation and outside air temperature The data cover typical values found on ships at sea hus if the elevation is 110 ft and the outside air temperature is 86 F the correction to get from station pressure to sea level pressure would be 3 8 mb In this case of this 3 8 mb only 0 2 mb is due to the air temperature which caused a lower than normal correction However if the air temperature had been a chilly 4 E the correction at 110 ft would be 4 6 mb of which 0 6 mb was due to the air temperature and this caused a higher than normal correction 49 4r 146 326 sor cor cor Tis os os os os os os 45 ao os os os 07 o oz
20. H susana 16 2 Show Graph Graph Pres aaa 16 Shortcut Graph Display eran 17 Average Pressure Dispara 18 Samples of Barograph Traces eee titres 19 22 Show Graph Graph Tendencias 20 2 3 Show Graph Tendency Code asaan sena brasa naasa 20 Pressure Tendency Characteristic Codes 22 Si MENU LOG PRESSURE napa 23 S Los o AAA Poe 23 32 Lao Pressure VEW EO SA 23 3 9 Log Pressure 7 Clear Entes amak 24 T MENU SET UP orion 24 4 1 Set up Units Time ODIO vaca 24 4 2 Set up Sea Level Pressure SLP anan ad asnala sas 25 Set Sea Level Pressure Dy Elevation annie 25 Set Sea Level Pressure by Pressure Value resorts 26 To Change from SLP back to Station Pressure 26 4 3 Set Up Station Pressure A uu seo poat d atit Od meal cix udis 27 cepas NG APAN AA 28 Na IHAIN CA 28 NG EN NG NA AA 29 Reset Pressure ESO Vestido 29 BOSeL tO nG LEA KO GAN AA AA 29 5 OPERATIONS mana a 30 5 1 Displays Following Power Interruption ssss 30 5 2 Connecting to the Duo from a Computer esses 30 Sue Editeurs ciis AMA Pon 37 SA Limited NAO A E o E AA Nep dri 37 5a CAG and CE GUN AA 97 ai sanla ec AU 38 5 7 Support Options and References eese 38 APRENDE cia M TN 39 Al Measuring elevation changes with the Mintaka Duo 39 A2 Sea Level Pressure vs Altimet
21. Lat Lon that offer accurate pressure online as well as providing a way to interpolate the data for time and location as well as a meth od to evaluate the consistency of the selected stations It also provides a way to correct your station pressure for the outside air temperature 43 A5 How to Find Accurate Elevation On Land Google Earth or equivalent online world mapping programs offer an accurate and precise way to find a local elevation Zoom in and read the elevation at the cursor The service at starpath com barometers also accesses this same elevation data set to provide accurate ground level elevations for specific locations given as Lat Lon Remember all such tabulated elevation data are the ground level The dis tance from ground to instrument height is called the removal and that is crucial for an accurate SLP and sometimes difficult to determine within a complex building Ihe removal however can be measured accurately with the Duo as outlined in Appendix Al On Water If you are installing the barometer on a vessel at sea and wish to read SLP as accurately as possible then you can assume that mean sea level is indeed the level of the water and the removal is the distance from water level to the barometer which is the only correction needed If your vessel is in tidal waters mean sea level will not likely coincide with the water level Mean sea level is very nearly equal to the mean tide level which is halfway between
22. application that you can use to type commands and receive responses here are many free terminal applications available on the Internet the examples below use the CoolTerm application available from www freeware the meiers org CoolTerm runs on Windows Mac and Linux computers Setting Up the Terminal Application The following examples are for the Mac version of Cool Term The Windows version and indeed other terminal applications are all similar Using the Options menu you need to set up a few parameters These include the port and the parameters for the port 22 000 TOTO Serial Port Serial Port Options Terminal Port usbserial DADOFFQE Im Receive Transmit Baudrate 57600 Miscellaneous Data Bits 8 Parity none Stop Bits AO Flow Control CTS JDTR XON Initial Line States when Port opens DTROn DTR Off RTS On C RTS Off Re 5can Serial Ports Cancel Sample set up screen for a terminal application In the above example the port is shown as usbserial DAOOFFQE You need to also set the following 1 Baud rate to 57600 the default for the Duo 2 Data bits to 8 3 Stop bits to 1 When you have accomplished this you can select the OK button and then press the Connect menu item Now type the character i for information and a return The Duo will respond with a screen of data about the barometer Below is an example
23. ated when power is applied This takes just seconds and will be indicated by a progress bar on the screen The longer the power out period the more data files that will update The files stored are listed in Table 1 3 There are 750 records in each file cozldz2213 14 41 13 File 3 entries 2 Station Pressure mb Progress bar shown during file refresh after a time without power The pressures stored and displayed in a graph after a power off period depend upon the period of time the power was off If the power is off for less than 15 minutes the pressure is recorded as constant equal to its value at the time of power off If the power if off for more than 15 minutes the pressure is recorded and displayed as zero meaning no data Thus short interruptions of power will not notably disrupt the graphs but longer periods will show a gap A graphic plot of pressures over a time range that includes a period without power more than 15 minutes will record the pressure as zero with a correspond ing gap in the plot and tabular history of pressures as shown below 1617 6 8 6H 4H Duo displays after the power was off from 0900 to 1130 on 7 13 Tendency data shown in the far right requires 3 hours of data so values shown will not be accurate until 3 hours of continuous operation Note too that the elevation must remain constant during the 3 hr period for the tendency to be correct Power interruptions of less than15 minutes show g
24. ation of 200 m 656 ft and the station pressure reads 1005 5 mb without any SLP corrections entered and then you set it to read SLP by entering the 200 m elevation the Duo will dis play a SLP of 1033 8 mb This correction of 23 8 mb accounts for the elevation of the instrument It is the same correction that any instrument that offers such an automatic correction would display unless it is simultaneously recording and averaging the outside air temperature This will usually be a good approximation to the SLP but it remains an approximation until the average outside air tempera ture is taken into account As noted earlier this form of SLP is called QNH We can correct this QNH for air temperature using the values in Table A1 In this example of 200 m elevation if the average outside air temperature had been 30 C 86 F then we should reduce the correction made by 1 3 mb In other words the displayed SLP of 1033 8 mb should be corrected to read 1032 5 mb This is then the pressure we would use to compare with official reports and weather maps For best results use the average of the air temperature at the time of observa tion and the value from 12 hours earlier T TO T 12h 2 In Table A1 the column headed T is the air temperature where this correc tion changes from to It is an indication of the air temperature that is used in the ISA for figuring QNH 47 The values in Table A1 are approximate corrections There are
25. ceding that time There is a mathe matical algorithm that defines the Code for any pressure pattern A pressure change of just 0 1 mb at either end of the 3 hr period can yield a different Code which illustrates the great value of this automatic function On this Duo screen you see the 3 hour trace that defines the tendency and its characteristic code The right side of the display shows the present pressure the characteristic code symbol the code value and at the bottom is the value of the tendency itself difference between present pressure and that of 3 hours earlier The tendency and the code values are updated every 15 seconds as new data changes the 3 hour history The codes are defined in Table 2 3 Each code has an associated WMO assigned graphic symbol These symbols are shown on weather maps that report Observations in a format that is called a station model As seen Table 2 4 some symbols cover more than one description of the 3 hr trace See Appendix A3 for related discussion 27 Table 2 3 WMO Pressure Tendency Characteristic Codes Pressure now higher than three hours ago Wx Map Symbol CU 10 Decreasing then increasing Pressure the same as three hours ago Description Wx Map Symbol Increasing then decreasing o lp Decreasing then increasing Pressure now lower than three hours ago Description Wx Map Symbol Decreasing then increasing V CUA Se masay 0 NT CE e A Steady then decreasing pet A
26. clear any log entries See Sec 3 for a description of the log entries facility See the DL and LE commands for displaying and creating log entries D dump records Command format d lt fileid gt count This command prints stored pressure information The lt fileid gt is an integer identifying the file of data to print Refer to the i command for file ids If lt file id is 1 the default then data from all files are printed If count is included the count most recent samples are printed for the specified file s If it is not included then all pressure samples are printed The samples are printed from oldest to most recent DEV dump event log Command format dev This command prints out the event log Significant events are logged includ ing when the Duo is started when the time is set any errors that may be encoun tered when the barometer is reset to factory settings among others DL dump log entries Command format d his command prints out any logged entries interspersed with the pressure samples taken at the synoptic times 0 00 6 00 12 00 18 00 UTC See Sec 3 for a description of the log entries facility See the CL and LE commands for clearing and creating log entries DM dump machine readable data Command format dm lt dataType gt This command is used to print information from the Duo in the JSON for mat This is a format that is easily parsed This command is useful for programs that
27. d 12 Table 1 1 Pressure Trend Arrows Anticipated 3 hr Pressure Symbol Description Change based on previous 1 hr history lt 1 mb Stationary lt 0 03 inHo Risin PEIUS 9 0 03 0 06 inHg Rising 2 3 mb Fast 0 06 0 09 inHg Rising gt 3 mb Very Fast gt 0 09 inHg Fallin Loma 9 0 03 0 06 inHg Falling 2 3 mb Fast 0 06 0 09 inHg Falling gt 3 mb Very Fast gt 0 09 inHg Table 1 2 Weather Warnings Broadly speaking Falling diagonal TAKE NOTICE arrow is a Take Notice signal Falling Fast one vertical arrow is the import ant Alert or Early Warning signal and Falling Very Fast two vertical arrows could well be already accompanied by bad weather or if not it should be PRESENT considered an Imminent Warning of OR potentially severe weather IMMINENT CHANGE E SNE 13 A convenient mnemonic for pressure change as a weather warning is the 4 5 6 guideline developed by Starpath School of Navigation which is intended to mean that any pressure change of 4 or 5 mb over a 6 hr period is fair warning of a change Less than that usually does not portend a significant change and much more than that is often well past the warning stage As further description of pressure changes used in numerical weather pre diction the NWS and WMO also define a Pressure Tendency Characteristic Code that describes the 3 hour pressure change ie decreasing then steady is Code 6 These characteristics usually r
28. d or you must correct the readings for it Therefore to make a careful elevation measurement you will need an inde pendent source of atmospheric pressure data over the region covered or return to the reference or base location to check the pressure after measuring it at the test location The Duo aids the elevation measurement if you do not have outside infor mation on the ambient pressure because it provides numerical values of the pressure tendency at all times Thus if your base pressure was 1014 5 with a ten dency of 0 6 and then at your test location 1 hour later the pressure was 1005 3 the first step would be to correct the test pressure for the expected change of 0 6 mb 3h x 1h 0 2 mb so the test pressure should be corrected to 1005 1 Then figure the elevation change as 1014 5 1005 1 mb x 12 ft 0 44mb 256 ft For more precise pressure readings you can view the Set up Adjust Station Pressure page to read the present pressure precise to 0 01 mb then Exit out of that page without changing any values You can return to it several times in a row to see if the value is stable For small elevation changes the extra precision could be helpful For accurate SLP measurements you need to know the instrument elevation above sea level In some locations you can measure this directly with the Duo by taking it from the permanent location down to sea level ie you live near the coast In other cases you find accurate ground el
29. e size of the horizontal divisions changes to match the vertical scale The present pressure was 1013 7 mb shown at the top right This display of present pressure will update once a second The vertical index lines mark 6 hr intervals in this display the two that are not labeled on the left are extensions of what is seen on the right namely 18H and 24H Each graph requires this projection to identify the last two lines as seen in the sample screens at the end of this section 17 The Station label at the top is a reminder that you are viewing Station Pres sure If the instrument had been set to sea level pressure that label would read SLP as a reminder The digital display of the pressure value shown at the time of the reading 1013 7 and the history plot are updated according to the time per pixel step in the display according to Table 1 3 To read digital values from the graph you can use a shortcut of pressing and holding either the or button This will display a digital readout window on top of the graph along with a vertical cursor line close spaced dots The but ton starts the cursor on the right of the screen the button starts it on the left ifii 7 E Pri2rid 2 12 88 1003 12H Pressure reading at the cursor position The readout shifts position as you move the cursor to keep the trace in view The readout shown corresponds to the value at the cursor line Once the cursor is showing the butt
30. e calibrations for individual instruments are available as an option Quick Start Instructions Plug the power adapter into a 120V AC outlet and connect to the barrel plug on the right side of the Duo After powering on the instrument the pressure in mb will be displayed Shortcut display options are shown on page 3 A full map of the menus is in Appendix A7 Specific instructions for each of the many features and options of the device are described in this Users Guide Pressure trend ar rows will not appear until the unit has been running for at least one hour Terminology and Applications Although other terms are often used only two values of atmospheric pressure matter for most applications station pressure and sea level pressure Station pressure is the value of the atmospheric pressure at the location and elevation of the instrument It is the weight of the atmosphere per unit area from the instruments elevation on up to the top of the atmosphere Sea level pressure on the other hand is a computed value of the pressure that is intended to represent what your instrument would read at this moment if it could hypothetically be lowered to sea level at your location When inland at an elevation of 300 ft above sea level it would be the pressure your instrument would read if you lowered it into a hole that was 300 ft deep As you lower it down there is more and more atmosphere above it so the weight of the air above it and the corr
31. ead from a barograph trace are submitted with all official observations They are then shown in station model reports on weather maps To assist observers with the often tedious task of evaluating this code the Duo offers the unique function of computing these codes automatically as explained in Sec 2 3 1 2 Show Values Clock Show Graph Log Pressure Set up Main Menu Show Values Clock The Duo includes a high precision clock that can be used for timekeeping as well as recording pressure histories The time and date can be set if needed in the in the Set up System Time menu Sec 4 4 The time zone is set in the Set up Units Time Zone menu The default time zone is 0 corresponding to Universal Time GMT The time of an event can be recorded in the Log Pressure Log Now option explained in Sec 3 1 This records the pressure and the time but it could be used to document the time of any event even if the pressure were not of interest at that time This has numerous applications in marine navigation r 15r14 UTO F r 15r14 TES 3 19 41 15 20 30 P1514 22 19 41 UTC P1514 22 28 28 UTC Show Values Clock Since weather reports and maps are mostly presented in terms of UTC GMT the Duo displays the current value of UTC on the clock display regard less of your primary time zone This also makes the clock display a valuable 14 addition to the nav station or wheelhouse of vessels at sea The clock has its own
32. er Pressure ss 40 A3 Pressure Tendency Characteristic Codes iria 41 A4 Where to Find Accurate Sea Level Pressure 42 A5 How to Find Accurate EIeyallOT soie sepe anna 43 ODE T 43 AI M 43 A6 Calibration Procedures racista 43 Ships Barometer COPTOctloTIsosstiesessines edited tempe sndice cade contes 48 na BB STOLE To rsa cheat O ARAY 50 6 INTRODUCTION Product Description and Options The Starpath Mintaka Duo Duo is an electronic barograph that mea sures atmospheric pressure using two independent high precision sensors The measured pressure can be presented digitally or as a graphic plot of historical values displayed over time ranges of the past 30 minutes on up to the past 120 days Numerous convenient display options are included to meet special needs of marine navigation engineering medicine and science The standard package includes the Duo barograph a 120V ACto 12V DC power adapter this Users Guide along with the Registration and Warranty Card An optional 6 ft cable with a matching DC barrel plug connector is available for direct wiring to a DC power source An optional version designed for remote sensing or connection to a Gill Pressure port is available This option has a 3 mm plastic tube with quick release pressure connector extending from the left side NIST traceable full pressure rang
33. esponding pressure increases as it lowers Sea level pressure is al ways higher than station pressure unless your barometer happened to be located below mean sea level which is possible at ground level at a few locations and often the case in mining applications 7 Depending on your application you will want to display either sea level pres sure or station pressure Sea level pressure is commonly abbreviated SLP Other terms and abbreviations are addressed in Appendix A2 If your main interest in atmospheric pressure is related to weather then you will most likely want to display sea level pressure SLP regardless of the location or elevation of your Duo Essentially all broadcast or published weather reports are given in terms of SLP and all weather maps identify the isobars of constant pressure in terms of SLP Furthermore if you are reporting your weather obser vations to another agency or broadcast station they will expect your reported pressure to be SLP hus if your application is weather related you will want to use the Set up option to adjust the instrument to show SLP You can make this adjustment one of two ways either from a known value of SLP at the time or from a known elevation of the instrument The step by step procedure is explained in this Users Guide It does not matter if you are in a boat with the instrument at 6 ft above sea level or in Sante Fe NM at 7 000 ft above sea level The procedure is the same for
34. evation as explained in Appen dix A5 and then add to this the elevation of the instrument above ground called 40 the removal Using the methods described above you can achieve an accurate measurement of the removal for any building the instrument is in A2 Sea Level Pressure vs Altimeter Pressure There are several ways to define sea level pressure which go beyond the even more complex concept of mean sea level itself For now we assume the reference level is clear but we look at the ways to describe the equivalent pressure at this level when observed at a higher elevation The most common way is to base the pressure change with elevation on the International Standard Atmosphere ISA This offers a fixed relationship between pressure and elevation that applies to all locations and all atmospheres The ISA elevation values can be obtained from a formula or from tables read ily available online This is the method that is used by essentially all electronic barometers that offer a correction to SLP based on the instrument elevation and itis also the one used by the Mintaka Duo It is also the same procedure used in US airports to report altimeter settings to aircraft which use the measured pressure to determine altitude so all aircraft are using the same reference It is sometimes abbreviated as QNH and in avia tion applications this value of sea level pressure is called the altimeter pressure or just altimeter This same abbrevia
35. evation offset to be 4500 feet SN view serial number Command format sn Print out the Duos serial number SO set read the station pressure offset Command format so xxxx x Sets the station pressure offset If no arguments are provided the current sta tion pressure offset is printed The default is a station pressure offset of 0 0 SS set read sensors Command format ss 0 1 0 1 Controls the Duos two sensors 0 disables a sensor and 1 enables it If no arguments are provided then the current status is printed The default is for both sensors to be enabled Example ss 0 1 turns off sensor 0 and turns on sensor 1 ST set read time Command format st mm dd yy hh mm ss Sets the current time in the currently selected timezone If no arguments are provided the current time is printed out 37 SU set read units Command format su 12 24 mb hPa inHg mmHg inH20 cmH20 kPa feet inches Sets the units used by the Duo with these arguments Clock format 12 or 24 for a 12h or 24h clock time default is 24h Pressure units mb hPa inHG mmHg inH2O cmH20 kPa default is mb Elevation units feet or meters default is feet If no arguments are provided SU prints the current units in use SZ set read timezone Command format sz 0 12 Set the current timezone Values from 12 to 12 are legal default is 0 for UTC If no arguments are provided the current timezone is printed 5 3 Maintenance
36. ghlighted option adjust the contrast id l 120V AC to 12V DC press and hold to change display power adapter between pressure value pressure or graph or tendency display direct to DC source Included in the box Barograph 120V AC to 12V DC power adapter User s Manual and Registration and Warranty Card Shortcut Display Options Once powered on all functions and displays can be reached from the screen menus explained in this Users Guide with full menu maps in Appendix A7 at the back of the book These single button shortcuts below are also available Press and hold SELECT to toggle through these main screens P1114 3 30i Asem 1009 1 gt Station Pressure mb l g UH 12H Contents Quick Start CI IB esce ctore etit eut aC ied ENAR 3 Shortcut Display Options erica 3 INTRODUCTION sana 6 Product Description and Options siesta rft spun tton eer etre p tuae iens 6 Quick Start Instructions nai litis 6 Terminology and Applications usada ud 6 How to Use this USC AA 7 lae CUA ICT AA E 8 Contrast 601 co E E EN E E pita 8 NOUS retira PP EE cane 8 Use of ihe Control bin eaten 9 139 4 ME S Pinto R rer Tm 9 EE nM YII OE EET 10 DEDEC WAN ossi ciere A AA 10 I MENU SHOW VALUES unan nono 10 show Values Pressure ostiis URB tnei 10 Pressure Trend Al OWS ocasion 11 12 how Wales COA RR UE 13 1 3 Show values LINO 14 How Data are Accumulated and Displayed 15 2 MENU SHOW GRAP
37. ifications To preserve the lifetime of the display screen and to facilitate mobile applications the screen light shuts off after 1 minute past the last button push The light comes back on automatically with the touch of any button There are numerous USB battery pack options available on the market with various storage capacities These are very compact units that also serve as backup power for cell phones and other devices A unit with 6 000 mA hr capacity will run the Duo in a portable mode continuously for about 4 days Disconnecting the power when not in use would extend this greatly In a portable mode the Duo can be used for pressure measurements away from other power options Portable operation can be used for accurate elevation measurements on land as outlined in Appendix Al Contrast Control If after changing power sources or for any reason you wish to adjust the display contrast this can be done by pressing and holding the EXIT button to access the Set Contrast screen then use or to adjust then use EXIT to highlight OK and press SELECT To exit without changing control highlight Cancel and press SELECT You can also access Set Contrast from the main menu EXIT Set up System Contrast Mounting You can mount the Duo on the wall or bulkhead using either two screws or with a piece of Velcro or Dual Lock removable fastener tapes Removable fasteners have been used for mounting similar devices on vessel
38. is to set it directly to a known value of the SLP at your location at the time you choose to set it The pro cedure for entering the digits is the same as described for entering an elevation earlier in this section See Appendix A4 for a discussion of obtaining accurate sea level pressure for your location Commercial weather broadcasts on radio or TV are a good start ing point but they may not be as dependable as more primary sources After entering a SLP here all other pressures reported in the instrument will be marked SLP as a reminder that you have entered this offset To Change from SLP back to Station Pressure When you change the display from Station Pressure to SLP by entering the correct SLP it is equivalent to entering the corresponding elevation for the instrument Thus when you return to the Set SLP by Elevation menu you will see the equivalent elevation has been filled in To return the instrument to reading Station Pressure simply change that elevation offset back to all zeros 27 4 3 Set up Station Pressure Adj Units Timezone Sensor 1018 55 Sea Level Pres Offset by 0 00 Station Pres Adj Toreag 015 57 System Ok Cancel Station Pressure Adjust menu Adjusting the station pressure readout is equivalent to calibrating the Duo relative to another pressure determination at the same time and elevation that is believed to be more accurate This is a completely different process from adjust ing the instru
39. ment to read SLP which is not related to the inherent accuracy of the pressure reading but just an offset of the values shown he station pressure adjustment changes the base readout of the instrument and should only be made if you have reason to believe the internal sensors of the instrument have drifted off of their initial calibration All barometers will drift to some extent over time and such an adjustment is normal procedure for all in struments aneroid and electronic What varies among instruments is how often they might need calibration and how much offset is needed This adjustment should not be made unless you have convincing evidence that it is needed Appendix A6 discusses the question of calibration and how to tell if it is needed In normal operation the Duo pressure should not drift more than 1 mb per year and there is no reason to believe they will drift that much A Please read Appendix A6 on Calibrations before changing the Station Pressure adjustment In the Station Pressure Adjust screen the pressure at the time you showed the menu is displayed to the maximum precision of the instrument This pressure is not updated by the sensors during the time this menu is in view Use the and SELECT to change the To Read value of the pressure to match the known SLP at your present time location The new pressure will be displayed as you enter the correction Input errors are not critical Just correct any typo until i
40. n find that function in the list of MENUS in the Table of Contents page 4 This will direct you to the pages that cover the topic An inserted cross reference such as Sec 2 4 means the topic at hand is further discussed in Section 2 4 A full map of the menus is in Appendix A7 Instrument Power The Duo requires an external source of power There are no internal batteries other than a long term gt 10 years cell that maintains the precision clock timer The instrument can be powered by any 9V to 30V DC source via the barrel plug connector on the right side A 12V AC DC adapter is provided When the Duo is connected to a computer the power is supplied by the com puter through the USB cable This 5V DC power source via USB connector is the same used by many cellphone chargers and other electronic devices A standard USB to mini B USB cable is required for this connection Alternatively you can plug the USB cable into any standard 5V USB power source for portable operation Twelve or 24V DC operation can be achieved with a cigarette lighter style USB adapter or an optional barrel plug power cable can be used to hardwire the device into a vessel or vehicles DC power system A portable USB power pack can be used for mobile applications The average current used is about 63 mA at 5V The average current used depends on how frequently the back lighting is being used At 12V the average current is about 38 mA See Sec 5 6 for detailed spec
41. n always turn it on from the graph by holding down a button A sample sequence of history displays is shown at the end of this section Average Pressure Display A unique feature of the Duo is the ability to show a running 12 hour average of the pressure This is of special value at low latitudes where the pressure typical ly oscillates on a fairly consistent pattern This semi diurnal variation is superim posed on all barograph traces in the tropics Barograph trace of Hurricane Sandy viewed from a vessel off the coast of Pana ma using an early version of the Mintaka Duo The semi diurnal pattern is clearly visible on top of the main ambient pressure change See expanded views below Below is a sample of a diurnal pattern with the pressure average line overlaid on the graph Dotted line is the 12 hr running average over 30 hr left and 5 days right As with normal display the button turns on the digital readout with active cursor control but when in this mode you see both the pressure at the average value at the cursor along with the actual pressure at that time Cursor readout with 12 hr average turned on The value in parenthesis is the average value at the time of the cursor position Samples of Barograph Traces 16011 0 i5H 10H EH Past 30 minutes imma 2uH 1zH Past 24 hours Past 2 days Past 4 days Sample sequence of history displays Not shown are 12 30 60 and 120 days The
42. o Gu E Cad Sample output from the information t command showing the file id numbers Recorded pressures are stored in a number of files see also Table 1 3 As shown above each file can hold a maximum of 750 entires Each file contains entries at a different collection time interval As indicated file 0 contains pressure data samples at 15 sec intervals whereas file 6 stores pressure data at 48 min in tervals File 8 at 6 hr intervals contains pressure data for midnight 00 00 06 00 12 00 18 00 UTC and so on Most of the other information is self explanatory The end of the report pres ents information on the two independent pressure sensors here are several commands explained below that allow you to access infor mation in the various files manipulate time and other information under the Barometer State heading in the Info i report 34 Individual Commands for Specific Information Command Syntax Data enclosed in square brackets is optional Data separated by vertical bars indicates the possible options that can be chosen A word enclosed in angle brackets xx is a place holder for a value The value is required unless included within square brackets CF clear file contents Command Format cf lt fileid gt Clears the contents of the indicated file The valid values for fileid file id can be seen by the i command CL clear log entries Command format cl This command is used to
43. ons move the cursor in either direction The single digit in the top right 1 at 1100 and 2 at 0212 is the Pressure Tendency Charac teristic Code value explained in Sec 2 3 It varies between 1 and 8 Press the EXIT to close the readout display Shortcut Graph Display When viewing the digital value of the pressure Show Value Pressure you can press and hold SELECT to directly display the Graph screen A second press and hold shows the tendency display screen and a third press and hold brings you back to the digital pressure An alternative way to set the graphic display scale as opposed to just Show Graph and using buttons is to Show Graph and then press SELECT once without holding This opens a new options screen step Eg Range 12h Show AYE No Cursor None LO Cancel Graph Options Menu from Select when viewing a graph Use to choose the desired range and press SELECT The full range of the 18 graph is shown in the top right of the display This will change as you change the step to show the corresponding range The next step asks to show the 24 hr average or not For most applications you would choose No The 24 hr average display is most important in the trop ics where there is a large semi diurnal variation in the pressure discussed below The last step is to choose to turn on the digital readout starting with cursor on the Left or Right or None The default None leaves it off you ca
44. ook An in depth look at barometers and applications of barometric pres sure by David Burch Starpath Publications 2008 39 APPENDIX A1 Measuring elevation changes with the Mintaka Duo The high precision of the Duo sensors allow it to be used for accurate relative elevation measurements Atmospheric pressure decreases with increasing eleva tion at a rate of about 0 44 mb per 12 ft If you call 12 ft a floor height you have the mnemonic Point four four per floor which is valid up to about 1 500 ft For example if at one elevation the pressure read 1015 5 mb and then you moved to a higher location where the pressure read 990 2 mb a pressure drop of 25 3 mb So the elevation change was 25 3 0 44 x 12 ft 690 ft Relatively small elevation changes cause much larger pressure changes than typical weather patterns do For this application you can run the Duo on a portable battery pack so it can be moved from one location to another without power interruption Alternative ly for some measurements you can simply unplug it at one elevation and move it to another elevation and plug it in again You will not accumulate pressure data during the movement but you still measure the pressure difference between the two locations which is needed to determine the elevation change For any relative elevation measurement however you must either assume the ambient atmospheric pressure over the region of your measurements has not change
45. r each code appear on surface analysis maps as shown below The national version of this map is available wpc ncep noaa gov sfc usdwmsfcbw pdf More detailed versions are available at the Weather Prediction Center and the Ocean Prediction Center Three station reports showing pressure tendency and characteristic he top right report is for 1012 4 mb a net drop of 1 2 mb 3h the tendency with a characteristic code 6 which could be decreasing then steady or decreasing then decreasing more slowly The significance is it has been going down and it has not started up again The codes are listed in Sec 2 3 he report on the left is for 1011 1 mb a net drop of 1 7 mb 3h and code 8 noting that regardless of what it did earlier it is now going down but since this is not a 6 it means there is no indication the descent has slowed 42 The bottom report is for 1013 2 mb with a net drop of just 0 8 mb with code 3 meaning it was decreasing and now it is increasing The values of these codes often add a dynamic quality to an otherwise static snapshot of the weather pattern The Mintaka Duo uses the computer algorithm recommended by the WMO to mathematically compute this code It is updated every 15 seconds because the precise value of the current pressure relative to that 3 hours ago affects the proper code choice A4 Where to Find Accurate Sea Level Pressure Unified Analysis weather maps from the Weather Prediction Center www
46. raph and tables at a constant pressure The graph will be flat during that short period of time 5 2 Connecting to the Duo from a Computer When your Duo is connected to a computer by a USB cable you can access it via a command line interface This provides a way to manipulate the instrument and extract information from it You can for example 31 e Display and download stored pressure data all or in part e Reset the stored data or reset to factory defaults e Create and access Logged entries e Display information on the state of the Duo e Read and set various parameters units time timezone etc e Display the event log Preparing your Computer to Read the Mintaka Duo When you connect the Duo to a computer via a USB cable a serial port is created on the computer You must however install drivers on your computer so the Duo is properly recognized The drivers and instruction on how to install them are available on this web page www ftdichip com Drivers VCP htm Once the drivers are installed a virtual com port will be created automatically when the Duo is plugged in On Windows computers this port will be in the form of a COMn port such as COMI COM etc On Mac computers this port will be in the form of a file in the file system such as dev tty usbserial xxxxxxxx The xxxxxxxx will be the serial number associated with your Duo Once you have the drivers installed and your Duo plugged in you need a terminal
47. ressure SLP You can use a known value of the SLP at the present time and location of the instru ment or you can use the known elevation of the instrument at its present loca tion The choice is made using the buttons when the SLP menu first appears which will change the mode in the highlighted area Sel IE ATION Tre SET TeSSUPE TO M 00 000 00 000 Cancel Cancel Set SLP by elevation offset or by known SLP Use to toggle the choice then SELECT to see the screens below where the data are entered Set Elevation Offset Set Pressure ta SL P 0 000 0120 Cancel Cancel Set Sea Level Pressure by Elevation After selecting Set by Elevation Offset the first digit on the left of the ele vation input will be highlighted and ready to change Use the buttons to set this digit correctly and then press Select After all digits are entered correctly highlight OK and press SELECT You can move the highlight with SELECT or EXIT Likewise to cancel the operation highlight Cancel and press SELECT For example from the above screen to enter 130 ft you would press SELECT twice to get to the hundreds digit then press the key once then SELECT then key three times then 26 SELECT and again SELECT to enter the final 0 and one more SELECT to highlight OK and a final SELECT to record your elevation The proper elevation to use would be the elevation of the ground at your location plu
48. rval There are 750 values stored in each data file They can all be viewed in tabular format from the History display The data field is selected from the History dis play There is an additional tabular history display in 1 hr steps All stored data can be exported to a spreadsheet with a computer connection as explained in Sec 5 2 These data can also be viewed as a barograph trace over the same time intervals The graphic display shows the past 120 points in each category In the barograph mode individual pressures can be read digitally using the cursor read out Sec 2 1 How Data are Accumulated and Displayed The Duo reads the pressure once a second in each sensor and then averag es 10 consecutive samples and displays that average value on the screen every second Thus the pressure seen on the screen updating each second is the average of 20 pressure readings one from each sensor over the past 10 seconds If for any reason it might be desired either of the sensors can be shut off to read the results of just one of them See Sec 5 2 Every 15 seconds the value displayed on the screen is stored in the 30 min file see Table 1 3 and every 90 seconds the displayed value is stored in the 3 hr file Likewise every 3 min an entry is stored in the 6 hr file and so on Thus in reviewing the history you see the values measured at the precise times stored with each data point That is each point stored in a table is an average over ju
49. s at sea for many years Dimensions are shown below to assist with screw mounting 40 mm 13 mm gt ke 6 mm 92 5 mm 98 5 mm Wall or bulkhead mounting by screws or fastener tape Use of the Control Buttons Duo functions are selected from the screen menus of options with the aid of four control Buttons SELECT and EXIT In this Users Guide we use the notation to mean either or as needed EXIT Button The EXIT button exits from the present screen or menu option From a data screen it exits to a menu screen and from a menu screen it exits to a data screen If you want to interact with the device the EXIT button is the first button to push If you enter a menu and decide you do not want to change anything press EXIT again to return to the data 10 On menu screens with multiple input options you can also use EXIT to exit that option and go to the next without changing anything These screens include specific OK or Cancel options so you can double check all settings before accept ing or exiting that menu and Buttons The buttons are used to move a highlighted selection up and down a ver tical menu to raise or lower a numerical value or to move a cursor to the right or left when viewing a graph Use of the and Buttons em numbers curso em o n SELECT Button The SELECT button is used to accept choices displayed on a highlighted section of
50. s the additional height of the instrument above ground level This additional height above the ground is called the Removal Correction This will then correct the pressure to sea level and store that elevation Once this elevation has been entered your display screens will be labeled SLP which is a reminder that you are reading the equivalent sea level pressure To return to Station Pressure repeat the process and enter all zeros for the elevation offset This correction can be entered when the instrument is at any location but the displayed sea level pressure would only be correct when the instrument is located at the elevation entered and stored in the unit The accuracy of the displayed SLP depends on the accuracy of the elevation offset that is entered The pressure changes at a rate of 0 44 mb per 12 ft so an error of 6 ft would cause a display error of about 0 2 mb Accurate ground eleva tions can be found from a topographic map or from online services like Google Earth or other sources listed in Appendix A4 he accuracy of the SLP relative to Weather Service reports can also de pend somewhat on the actual elevation At higher elevations the most accurate conversion from Station Pressure to Sea Level Pressure depends on the outside air temperature as well as the elevation This detail and standard corrections are addressed in Appendix A2 Set Sea Level Pressure by Pressure Value he alternative way to set the instrument to SLP
51. ssure entry Command format le Add the current pressure into the logged pressure entries See Sec 3 for a de scription of the log entries facility See the DL and CL commands for displaying and clearing log entries RESET reset to factory defaults Command format reset Reset the Duo to factory defaults all recorded history is deleted RESETH reset pressure history Command format reseth Erase all recorded pressure samples 36 SA set read the running average count Command format sa 12 24 Print out if no argument is provided or set the number of entries used for calculating the running average displayed in the graphical displays Either 12 or 24 hourly entries on the hour can be specified The default is 12 SB set read baud rate Command format sb 1200 9600 28800 57600 115200 Set the baud rate used for serial communication via the USB port The default is 57600 SC set read LCD contrast Command format sc 0 100 Set the contrast for the LCD display If no arguments are provided the current contrast value is printed SE set read elevation offset Command format se E P xxxx x Sets the elevation offset As with the graphical user interface the elevation offset can be either set by a pressure value if P is provided or an elevation value if E is provided If no arguments are provided the current offset is printed The default is an elevation offset of 0 Example se E 4500 sets the el
52. st 10 seconds not an average over the time step of the file The data values at the synoptic times used in weather analysis are also auto matically stored in a separate file for quick reference Sec 3 16 The numerical value of the pressure tendency is a WMO NWS official param eter defined as the change in pressure over the past three hours Pressure tendency Pressure now Pressure exactly three hours earlier A positive tendency means the pressure has increased over this period a minus tendency means it has decreased Consequently tendency values are not presented until the instrument has been running for at least three hours 2 MENU SHOW GRAPH 2 1 Show Graph Graph Pressure n Log Pressure Set up Graph Tendency Tendency Code Main Menu Show Graph Graph Pressure The first graph range seen will be the last one that was viewed To change the full range displayed use the buttons to step through the options listed in Table 1 3 1999 6 12H Barograph trace for the past 24 hours It updates every 12 min Optional dis plays are listed in Table 1 3 Samples are shown at the end of this section The top right shows the present pressure which updates every second The vertical scale of each barograph display is computed automatically to span the display and shown on the left In this example the top of the display is 1015 mb and the bottom is 1009 mb and each horizontal division is 1 mb Th
53. stored values at the synoptic times When logging a pressure manually a window shows briefly acknowledging your entry then the list of en tries is presented Manually entered pressures can be removed with the Clear En tries option Sec 3 3 Manually logged pressures are stored in UTC even though you might be using a different time zone for the clock and barograph displays You can also use this feature to record accurate time to the second of any event even if the pressure itself is not the motivation for the entry Need for such a record comes up often in marine navigation It could also be valuable when using the Duo for accurate elevation measurements on land Appendix A1 3 2 Log Pressure View Entries This option shows the list of logged pressures both automatic and manual The buttons are used to page through the stored values a total of 750 points 187 5 days of synoptic times plus up to 25 manually entered pressures Log Pressure display showing 2 manually entered pressures along with 5 auto matically recorded synoptic time values pages through the data 3 3 Log Pressure Clear Entries To remove the manually added records from the Log choose Clear Entries A window appears then to ask for your confirmation or you can cancel without removing these data from the Log This Clearing removes the pressure records added manually but leaves the synoptic time records All pressures however are still stored in the
54. t shows properly Once this shows the pressure you wish to have highlight OK and press SELECT he offset you enter here will be removed if you Reset to factory settings Sec 4 4 so if you have chosen to enter one it could be useful to record it before resetting to factory settings This setting is not affected by Reset pressure history 28 4 4 Set up System Units Timezone Sea Level Pres Station Pres Adj SE Contrast Set up System Menu Set up System Time TimeUTC 0 EXT 01 2013 223316 DK Cancel Set up System Time Menu Use this screen to set the Duo to a precise clock time using the time zone se lected in the Set up Units Time Zone screen Sec 4 1 Step through the options using the and SELECT then step to OK and press SELECT The time display 12h or 24h is selected in the Set up Units Time Zone screen Sec 4 1 The default time zone is 0 corresponding to UTC The time zone can later be changed to best meet your needs Caution Pressing OK on this screen will adjust the clock to the time that is shown If the clock time was correct to begin with choose Cancel to leave without chang ing the clock time In other words if the clock was right and you just viewed this screen to see what it looks like and then chose OK you would lose clock accuracy because the time shown is not changing as you watch it If the clock time is correct and you just want to change the time zone
55. ta When you make this selection you are presented with the option to confirm this choice or cancel Reseting the pressure history will not change any of your set up choic es and will not change the SLP Elevation Offset nor any Station Pressure Offset that might have been entered Pressure change arrows will then not be active until 1 hour after this selection pressure tendency will be available after 3 hours Reset to Factory Settings This Reset option returns the Duo to all of the settings and configuration it had when it was shipped from the factory All pressure history will be erased along with all Set up choices that might have been entered The time zone is set back to 0 but the time and date running in the clock are not changed A Caution If you have entered in a Station Pressure offset it too will be erased with this choice You can check this first Sec 4 3 and make note of this status The only thing that is not changed in a Factory reset is the time and date pres ently stored in the device A warning screen with a reminder of the above with the option to cancel is presented if this choice is selected 30 5 OPERATIONS 5 1 Displays Following Power Interruption The Duo clock has its own long term battery so timekeeping is not interrupt ed when power is removed from the unit Without power pressures are not being recorded but the clock is still running Thus the several data files of pressure re cords need to be upd
56. tion system called Q codes which originated in early radio and telegraph applications uses the letters QFE to label station pressure hus the pressure reported by the Duo and almost all electronic barometers as SLP is the same as the altimeter reading one might see in aviation weather reports It is also the same pressure that is usually referred to in print and broad casts as the sea level pressure Meteorologists however have long known that other factors besides eleva tion affect the choice for the best local equivalent atmospheric pressure at sea level when measured at a higher elevation on land The abbreviation for this best estimate of the sea level pressure is QFF The main factor that can cause a difference between QFF and QNH ie between best SLP and altimeter SLP is the average temperature of the outside air over the past 12 hours Humidity has a very small effect but there can also be small unique local geographic factors called Plateau Correction that vary from place to place In short there is no simple formula to convert station pressure QFE measured at elevation to its best equivalent sea level pressure QFF In practice we apply the ISA elevation correction to QFE station pressure to get ONH altimeter which is usually a very good approximation to QFF sea level pressure reported by NWS For elevations below 1 000 ft or so and for seasonal temperatures the differ ences are small but notable Table A1 sho
57. ws approximate air temperature correc tions that can improve this conversion at various elevations and temperatures 41 Terminology Review QFE Q code for Station pressure The atmospheric pressure read from a ba rometer at its present elevation When an aircraft altimeter is set to QFE station pressure at the airport it will read the height of the aircraft above ground when off the ground and it will read zero when on the air strip QNH Q code for Sea Level pressure figured at a particular location using only the elevation of the place to make the conversion using the International Standard Atmosphere Also called Altimeter When an aircraft altimeter is set to ONH it will read the altitude of the aircraft above mean sea level when off the ground and it will read the elevation of the airport when on the air strip QFF Q code for sea level pressure taking into account all properties of the actual atmosphere present at the time plus special correction factors Plateau Correction unique to some high locations A3 Pressure Tendency Characteristic Codes Pressure Tendency Characteristic Codes Sec 2 3 are defined and discussed in the National Weather Service Observing Handbook No 1 which is available online at the NWS Voluntary Observing Ship website www vos noaa gov These important data are assimilated into numerical weather prediction models and they are also used for pressure data quality control analysis The symbols used fo
58. x ox Duo S TARPATI PV irs tal Dual Sensor Precision Barograph DAS OFFQ7 SELECT EXIT Published by Starpath Publications 3050 NW 63rd Street Seattle WA 98107 starpathpublications com 1 206 783 1414 Copyright O 2014 Starpath Publications All rights reserved No part of this book may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying recording or any information storage or retrieval system without permission in writing from the publisher Manufactured in the United States of America Please note that this Users Guide does not create any legally binding obligations for Starpath Corporation or Mintaka Instruments LLC towards the customer or end user All legally binding commitments and agreements are included exclusively in the appropriate supply contract or Conditions of Sale kx XK ox MINTAKA An SIARPATH N Quick Start Guide Battery Pack Plug for optional connection to Gill Port for remote pressure sensing POWER OPTIONS ome AC Adapter Mintala STARPATH DUAL SENSOR PRECISION BAROGRAPH Mini USB o 7721714 11 17 41am pe CUM 1012 9 gt Sea Leuel Pres a Unique ID and S N DAS SFFQ7 9V 30V DC gt 0 Ta SELECT EXIT Lp M or T EXIT E to step selection or cursor current display up down or left right SERA NAG nl or to previous display Or press and hold to SELECT hi
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