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CALIBRATION

Page 19

CALIBRATION CYCLE

The porometer is automatically cycling and taking measurements of the transit time.

This is the time it takes the calibration plate to release enough moisture to raise the cup
RH by a fixed amount.

Dry air is then pumped through the chamber until the RH is a few percent below the set
point.

The cycle repeats until you press GO to ACCEPT the last reading.

CYCLE SETTINGS

Beeping :

ON or OFF

This refers to a small loudspeaker.
When ON, it goes "Beep-beep" if two consecutive readings are within 2%.

CALIBRATION CYCLE

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Summary of Contents for AP4

Page 1: ...User Manual for the AP4 Porometer Version 4 Delta T Devices Version 4 0 ...

Page 2: ...gnof thesoftware menu and the Department of Trade and Industry for a grant towards the design Ian Woodward and Colin Black are thanked for testing early prototypes John Monteith and Gaylon Campbell are thanked for their work on the theory John Monteith and Edward Arnold Publishers are thanked for permission to reprint an extract from Principles of Environmental Physics Jonathan Price is thanked fo...

Page 3: ...NT 7 Unpacking 8 YOU SHOULD HAVE 8 OPTIONAL ACCESSORIES 8 YOU WILL ALSO NEED 8 How to Use the AP4 9 SETTING UP AND SHUTTING DOWN 9 SETTING UP 9 A TYPICAL MEASUREMENT SESSION 10 MEASURMENTS WITH ONE HAND 11 CALIBRATION 12 PREPARATION 12 WETTING THE FILTER PAD 13 STICK DOWN THE PAD 14 CALIBRATION LOOP 15 INSERT PLATE SCREEN 17 CALIBRATE SETTINGS SCREEN 17 CALIBRATE SETTINGS 18 CALIBRATION CYCLE 19 C...

Page 4: ...ADINGS CYCLE FLOW CHART 32 STORE READINGS 33 STORE READINGS FLOW CHART 34 REVIEW 35 OUTPUT TO COMPUTER 36 REQUIREMENTS 36 Run AP4 Retrieve on your PC 36 TYPICAL PRINT OUT OF DATA 38 Planning Your Experiment 39 CHECKS 39 HOW MANY READINGS TO TAKE 40 MEMORY USAGE 40 EXAMPLE PLAN 40 HOW TO CALCULATE AVAILABLE MEMORY 41 Hints and Tips 42 IN TRANSIT 42 THE FIRST RUN OF THE DAY 42 CHOICE OF CUP 43 LEAF ...

Page 5: ...ifications 55 SENSOR HEAD 55 CONTROL UNIT 55 CABLES 56 DATA COLLECTION SOFTWARE 56 OPERATING LIMITS 56 CALIBRATION PLATE VALUES At 20 C 1000 hPa 57 PERFORMANCE SPECIFICATIONS cont d 58 CE CONFORMITY 59 Warranty Service Technical Support 60 Terms and Conditions of Sale 60 Service Repairs and Spares 61 Technical Support 61 Contact details 61 Index 62 ...

Page 6: ...Campbell Potter 1988 backed up by our considerable manufacturing experience of this type of instrument and has been in world wide use for over thirty years The AP4 corrects for changes in temperature Readings are automatically converted into units of resistance or conductance and can be annotated displayed saved and output to a computer or printer Menu driven software a 40 character by 8 line liqu...

Page 7: ...E BY EXCESSIVE HANDLING OR EXPOSURE TO THERMAL RADIATION DO NOT LEAVE A LEAF OR THE CALIBRATION PLATE IN THE HEAD WHEN THE AP4 IS NOT CYCLING WHOLE INSTRUMENT AVOID STORAGE OR USE ABOVE 80 RH PROTECT THE AP4 FROM WATER AVOID DEEP DISCHARGE OF BATTERY See How to Service Battery on page 11 of the AP4 Technical Manual DO NOT CONNECT BATTERY CHARGER TO THE WRONG MAINS VOLTAGE YOUR ENVIRONMENT DISPOSE ...

Page 8: ...meter wristwatch type PBR1 Spare sensor head type PSH1 Spare AP4 re chargeable battery type PSB1 YOU WILL ALSO NEED Internet access to https www delta t co uk software ap4 retrieve 1 1 for a copy of AP4 Retrieve Release Notes the AP4 Retrieve software and the AP4 Technical Manual pdf Please read AP4 Retrieve Release Notes to establish what Windows operating systems are supported by the current ver...

Page 9: ...omeone was using it and has left readings in it To free memory output readings to a computer see page 36 then delete readings via OUTPUT DISCARD Shutting down for less than two weeks Press OFF button twice Place head and cable in pocket provided Zip up case Protect from dust humidity greater than 80 smoke and organic solvent fumes and other pollutants Shutting down long term Charge battery Recharg...

Page 10: ...on data if curve errors are less than 10 Select READ Put leaf in head Select START The AP4 starts taking readings Wait for steady readings or double beep sound ACCEPT the stomatal conductance reading Remove the head from the leaf and angle the head so that the PAR sensor is level with the leaf Select STORE to keep the reading or DISCARD to start again EXIT to return to the main menu REVIEW the dat...

Page 11: ...https youtu be kA7yS8JJsLE Insert leaf Turn AP4 on TO TAKE A READING with one hand Wait 4 or 5 cycles until readings are steady or until Beep Beep sounds MAIN MENU READ CALIBRATE REVIEW OUTPUT ON INSERT lEAF START READING CYCLE ACCEPT MAIN MENU STORE DISCARD 1 2 GO 5 7 GO 4 GO GO 6 Press GO Press GO Press GO 3 1 2 3 2 2 46 3 2 45 s cm 1 Press GO to store or GO to discard ...

Page 12: ...kes 5 ml Tissue paper or blotting paper You may wish to use a barometer such as the wristwatch style one which we can supply as an accessory Without it a 100 hPa mbar pressure change or a 1000 m change in altitude will cause a 10 error in measured resistance If the pressure does not change significantly between calibration and measurement then you can get away without a barometer See Pressure on p...

Page 13: ...BRATION Page 13 WETTING THE FILTER PAD Wet the paper all over with distilled water Remove the excess water with blotting paper or absorbent tissue paper Repeat two more times with fresh dry absorbent paper ...

Page 14: ...ooth down the tape to remove any air pockets Return the calibration plate to its plastic zipper lock bag until needed This will slow down the rate at which it dries out and also keeps it clean In our experience in the U K it has stayed damp for three days if kept in its bag Smooth down the tape to remove any air pockets Protect the plate from greasy fingers Leave for about 1 hour before calibratin...

Page 15: ...ically keeps track of where you are Calibration Flow Chart MAIN MENU INSERT PLATE CALIBRATION SETTINGS Position Cup Type Order Pressure CALIBRATION CYCLE CYCLE SETTINGS CYCLE Beeping INSTALL CALIBRATION INSTALL FIT CURVE ACCEPT Units RH Set REDO READ CALIBRATE REVIEW OUTPUT WAITING CHOOSE WAITING GET READY SET RH CHOOSE PLATE POSTION CUP TYPE UNITS INSERT PLATE GO GO CYCLING CONTINUOUSLY READING W...

Page 16: ...ORE Notes Leaf Plant DISCARD REVIEW EXIT Group Reading INSERT PLATE CALIBRATION SETTINGS Position Cup Type Order Pressure CALIBRATION CYCLE CYCLE SETTINGS CYCLE Beeping INSTALL CALIBRATION INSTALL FIT CURVE ACCEPT Units RH Set REDO OUTPUT READINGS OUTPUT SETTINGS From group Baud rate Parity none Handshake SEND DELETE Data bits 8 Stop bits 1 SENDING READINGS PAUSE RESUME CONFIGURE AP4 HEAD CURVE FI...

Page 17: ...to temporarily disable the pump 2 Open the head and wave it about 3 Read the Head RH to determine the ambient RH 4 Adjust the Set RH value with the or key to be close to and just below the ambient RH example if ambient is 43 set to 40 5 Press SET to call up and change any of the default values on the settings screen 6 Press GO or EXIT to return to the INSERT PLATE screen 7 Insert the plate at the ...

Page 18: ... Technical Manual at www delta t co uk CALIBRATE SETTINGS EFFECT OF ALTITUDE ON AVERAGE BAROMETRIC PRESSURE TYPICAL EFFECT OF UK WEATHER ON BAROMETRIC PRESSURE ALTITUDE ALTITUDE 5000 m 0 0 1000 500 1030 980 mbar mbar TIME HOURS 200 100 0 ...

Page 19: ... release enough moisture to raise the cup RH by a fixed amount Dry air is then pumped through the chamber until the RH is a few percent below the set point The cycle repeats until you press GO to ACCEPT the last reading CYCLE SETTINGS Beeping ON or OFF This refers to a small loudspeaker When ON it goes Beep beep if two consecutive readings are within 2 CALIBRATION CYCLE ...

Page 20: ... if these two readings are wildly different Wait until you have worked through or at least attempted to work through all 6 plate positions and then accepted the curve fit option which will appear later After that the results will be recalculated using the current measured transit times and theoretical plate values as data The two sets of readings should then match quite closely Wait until then bef...

Page 21: ...CALIBRATION Page 21 ...

Page 22: ...dard deviation of the residual errors This figure is useful when calibrating to check that the calibration ran OK If the error is less than 10 then go ahead and INSTALL it If between 10 to 15 then redo the worst reading in the results column The porometer is accurate to 20 once it is accurately calibrated The spread on your readings should be better than this If the error is greater than 10 the cu...

Page 23: ...CALIBRATION Page 23 INSTALL CALIBRATION FLOW CHART ...

Page 24: ...mbar Insert damp calibration plate at position 1 Ensure it fits snugly Press GO to start the reading Wait until readings are stable then press GO to ACCEPT it Move plate to next position and repeat until all 6 positions are read Select CURVE FIT The porometer then fits a calibration curve to the data recalculates the results and estimates the error INSTALL if the error is less than 10 Otherwise DI...

Page 25: ... page 42 THE READING LOOP Readings can be taken one handed Just press the GO button on the head YOUR ACTION POROMETER ACTION DISPLAY TITLE Press ON Porometer wakes up MAIN MENU Press GO Selects READ loop INSERT LEAF Insert leaf Waits Press GO wait Selects START option Starts cycling READING CYCLE updated with every reading Wait 4 or 5 cycles until readings are stable or until double beep sounds Pr...

Page 26: ...and Wait 4 or 5 cycles until readings are steady or until Beep Beep sounds MAIN MENU READ CALIBRATE REVIEW OUTPUT ON INSERT lEAF START READING CYCLE ACCEPT MAIN MENU STORE DISCARD 1 2 GO 5 7 GO 4 GO GO 6 Press GO Press GO Press GO 3 1 2 3 2 2 46 3 2 45 s cm 1 Press GO to store or GO to discard ...

Page 27: ...GO button Some of the action screens have information displayed in inverse video This can be changed using the and keys Most action screens have a settings screen behind them You can bring them forwards with the SET button This is where you go to change most of the settings Use the key to highlight each option and change them with the and keys in the normal way Press HELP if you get stuck See also...

Page 28: ...mol 1 s cm 1 s m 1 mmol m 2 s 1 600 to 1200 hPa mbar CALIBRATE INSERT PLATE Position Set RH 1 to 6 5 to 80 CALIBRATE INSERT PLATE SET Cup type Order Units Pressure slotted or circular 1 to 6 or 6 to 1 as above OUTPUT OUTPUT READINGS From group 1 255 OUTPUT OUTPUT READINGS SET send as Parity Data bits Stop bits Handshake csv or text none 8 1 hardware or none SHIFT KEY OFF together use when installi...

Page 29: ... If the pump comes on press or This disables the pump until you press GO Recalibrate when you change the RH Set point You may alter the leaf and plant number if you wish This will never cause you to lose data The AP4 will automatically increment the leaf number if you do nothing The AP4 stores readings in groups which you can name via the keyboard Each group is also given a number which you cannot...

Page 30: ...HOW TO READ Page 30 ...

Page 31: ...CREEN Beeping ON OFF This refers to a small loudspeaker When ON it goes Beep beep if two consecutive readings are within 2 Combined with the use of the GO button on the porometer head this allows you to take and store readings without needing to look at the screen at all Units s m 1 Resistance s cm 1 m2 s mol 1 mm s 1 Conductance cm s 1 mmol m 2 s 1 See also Resistance and Conductance Units in the...

Page 32: ...HOW TO READ Page 32 READINGS CYCLE FLOW CHART ...

Page 33: ...lly when you do this level with the leaf if possible STORE SETTINGS SCREEN The leaf number automatically increments by 1 every time you store a reading You can also change it manually if you wish with the and keys in the normal way Increment the plant number with the button when you change to another plant If you want to you can label your plants with these numbers You can label and read your plan...

Page 34: ...HOW TO READ Page 34 STORE READINGS FLOW CHART ...

Page 35: ...REVIEW Page 35 REVIEW No editing can be done and no settings changed within REVIEW ...

Page 36: ... One free USB port An AP4 RS232 cable and a USB adapter cable both supplied with the AP4 Run AP4 Retrieve on your PC You need local administrator rights to install AP4 Retrieve 1 1 Please contact your system administrator for further information Download AP4 Retrieve from www delta t co uk When the download completes right click on AP4Retrieve exe and select Run as Administrator The installation p...

Page 37: ...OUTPUT TO COMPUTER Page 37 The datais now copied to your PC AP4s are shipped with valid RS232 parameters set These RS232 parameters should also work OK 1 2 3 3 6 ...

Page 38: ...OUTPUT TO COMPUTER Page 38 TYPICAL PRINT OUT OF DATA 17 ...

Page 39: ...ration Kit Anywhere Do you have Calibration plate Filter pad Tape Blotting paper or tissue Scissors Distilled water Refresh calibration plate with damp filter paper Page 12 Cup shape Sensor head Slotted or round Select Tech Manual page 17 In the AP4 Technical Manual Are you ready Check that you know the following How to calibrate and when How to record and output the data What you are going to mea...

Page 40: ...main title can also be up to 16 characters long Each group is identified by a number as is each plant and each leaf EXAMPLE PLAN Title My first attempt Number of groups 4 Group names will be Treatment 1 Treatment 2 Treatment 3 Treatment 4 Number of plants in each group 5 Number of leaves per plant 5 So total number of readings 4 x 5 x 5 100 At one reading per minute expect to take about 2 hours Ba...

Page 41: ...e a memory left b number of groups of data number of experimental plots for instance c average length of annotation to 30 characters Example 1 Given No notes 1 group Maximum number of readings 32000 44 20 1597 readings 1 reading every 18 seconds for 8 hours Example 2 Given 30 characters of notes per reading 16 groups of readings Maximum number of readings 32000 16 𝑥 44 20 30 625 readings 1 reading...

Page 42: ... 15 At 20 C and 50 RH we found that the calibration plate will stay fresh with its measured resistance within 5 for several days in its wallet and up to 18 hours out of the wallet It will be shorter at higher temperatures and lower RH s Make up the plate the day before This may also be a convenient time to make sure the correct cup shape is installed in the sensor head When starting up the AP4 fir...

Page 43: ...e and texture of leaf surfaces you are trying to measure The leaf must cover the whole of the cup aperture you can view the cup through the rubber pad to check this In general the slotted cup is preferable because it covers a larger area Leaf stomata can be very unevenly distributed The other consideration is contact between the leaf and the rubber seal around the cup rim The circular cup shape mi...

Page 44: ...tly above air temperature Excessive handling will also warm it up Leaves may be either hotter or cooler than air temperature depending on their stomatal aperture water stress and a number of other factors As far as possible therefore keep the sensor head shaded and the shutter over the leaf pad closed If the δT can be kept 1 C you are doing well The AP4 software will be applying its automatic corr...

Page 45: ... quantum sensor but no levelling device is provided After a resistance reading has been accepted and the sensor head unclipped from the leaf the light sensor should be oriented in the plane of the leaf The irradiance reading will be frozen at the moment of storing the data An irradiance value will get stored for every reading whether you want it or not so note which are the valid readings CLEANING...

Page 46: ...the current advice from the desiccant manufacturer is not to attempt to regenerate the desiccant by heating but to replace it They also say desiccant is damaged above 120 C A 500 g pot of 2 5 mm beads of orange to green self indicating silica gel is currently supplied with each AP4 The amount used in the AP4 silica gel tube is about 16 g so the pot may supply about 30 refills if you store the pot ...

Page 47: ... head Opposite the cup a second microchip thermistor is buried in the translucent flexible silicon rubber pad These measure the cup and leaf temperatures respectively One control button is mounted next to the light sensor The cable attached to the head contains a tube for air as well as signal wires The tubing plugs into a container of self indicating desiccant located in the pocket to the left of...

Page 48: ...board on the case of the porometer does not control the porometer It is just used for adding optional notes to readings and for entering the titles of groups of readings Below the keyboard from left to right are located the socket for the head lead a knob to adjust the screen contrast an input socket with a red light for the battery charger and an RS232C serial interface socket for sending data to...

Page 49: ...Layout and Control Page 49 ...

Page 50: ...ng Page 11 in the AP4 Technical Manual The HELP key provides context sensitive information on what to do next Up to 7 screens of help may be provided Press HELP again to read the next screen Press any other key to return to the program The EXIT key is used to leave a menu without selecting any option The program returns to the next higher menu level Use it to go back ON OFF HELP EXIT ON OFF HELP E...

Page 51: ...s GO Insert leaf Press GO Wait Press GO Press GO Wake up Select READ loop Waiting START reading Continues ACCEPTS reading STORES result OFF MAIN MENU INSERT LEAF INSERT LEAF READING CYCLE READING CYCLE STORE READING INSERT LEAF THIS PERMITS ONE HANDED OPERATION OF THE POROMETER At any stage other options can be selected via the key or the previous menu can be selected via the EXIT key Display Flas...

Page 52: ...e See also Light sensor calibration Page 23 in the AP4 Technical Manual Thermistor calibration Page 26 in the AP4 Technical Manual Accessing the SET SCREEN will display three head calibration coefficients used to characterise water absorption in the cup These are automatically used to calculate the results Only theoreticians and other experts will be interested in this Next option identified READ ...

Page 53: ...e plus and minus key are used to change default settings Example To change the date USER ACTION POROMETER ACTION DISPLAY Asleep OFF Press ON Wakes MAIN MENU Press SET Day of month CLOCK SETTINGS shownin inverse video Press Day of month increments Press GO Acceptschange returns to MAIN MENU SET SET KEY PLUS KEY MINUS KEY READ CALIBRATE OUTPUT REVIEW MAIN MENU 30 5 19 14 20 Bat 97 Mem 87 CLOCK SETTI...

Page 54: ...TORE SETTINGS STORE Notes Leaf Plant DISCARD REVIEW EXIT Group Reading INSERT PLATE CALIBRATION SETTINGS Position Cup Type Order Pressure CALIBRATION CYCLE CYCLE SETTINGS CYCLE Beeping INSTALL CALIBRATION INSTALL FIT CURVE ACCEPT Units RH Set REDO OUTPUT READINGS OUTPUT SETTINGS From group Baud rate Parity none Handshake SEND DELETE Data bits 8 Stop bits 1 SENDING READINGS PAUSE RESUME CONFIGURE A...

Page 55: ...y 0 1 C at 25 C 0 3 C at 0 and 50 C Light sensor Unfiltered GaAsP photodiode CONTROL UNIT Interface Control panel with 8 lines x 40 character LCD display QWERTY keypad for annotation RS232 interface Pocket for sensor head desiccant and calibration plate PROM Software Version 2 Functions Functions read calibrate review and output automatic calibration curve fitting automatic temperature correction ...

Page 56: ... 10 One free USB port and an internet connection AP4 Retrieve software Download from www delta t co uk OPERATING LIMITS Temperature 0 to 50 C Humidity 10 to 90 RH non condensing Battery Duration 20 h Life expectancy 200 to 2000 recharge cycles Charging 12 to 15 V dc 0 5 A Recharge time approx 14 hours Memory 32 Kbytes approx 630 to 1600 readings depending on the extent of added notes RS232 cable 2...

Page 57: ...00 hPa Plate position Resistance s cm s m m2 s mol Conductance cm s mm s mmol m2 s 1 27 3 2730 66 51 0 04 0 37 15 2 16 5 1650 40 02 0 06 0 61 25 3 7 4 740 18 03 0 14 1 35 55 4 3 1 310 7 55 0 32 3 23 132 5 1 6 160 3 90 0 63 6 25 257 6 0 8 80 1 95 1 25 12 50 513 ...

Page 58: ... of 5 hPa RH cycle level 20 80 RH settable insteps of 5 4 Notes 1 Resolutionvarieswiththemagnitudeofthevalueobtained Therangeshowncorresponds to the reading range In relative terms the resolution is better than 2 but at least the smallestamountshown 2 Accuracy is the extent with which the measurement agrees with the true value 100 is perfect as verified by comparing plate readings with the referen...

Page 59: ...E CONFORMITY ThePorometertype AP4conformsto ECregulations regarding electromagnetic emissionsand susceptibility when used according to the instructions contained within this user manual and is CE marked by Delta T Devices Ltd ...

Page 60: ... charge or by repairing the goods free of charge at Delta T s premises in the UK during the warranty period If Delta T requires that goods under warranty be returned to them from overseas for repair Delta T shall not be liable for the cost of carriage or for customs clearance in respect of such goods However Delta T requires that such returns are discussed with them in advance and may at their dis...

Page 61: ...ay We normally expect to complete repairs within one or two weeks of receiving the equipment However if the equipment has to be forwarded to our original supplier for specialist repairs or recalibration additional delays of a few weeks may be expected For contact details see below Technical Support Users in countries that have a Delta T distributor or technical representative should contact them i...

Page 62: ...preparation summary 24 CALIBRATION PLATE VALUES 57 carrying bag 8 CE CONFORMITY 59 CHECKS 39 Computer 56 Conductance units 31 Configure AP4 Head 52 Contact details 61 control keys 48 Control panel 55 CUP choice 43 Cup apertures 55 cup temperature 31 Cup type 28 CYCLE SETTINGS 19 Data bits 28 Date 27 Date format 27 desiccant 47 Desiccant 39 DESICCANT 7 display 51 display panel 48 EXIT 50 File forma...

Page 63: ...gs 9 How to take readings 25 Readings loop 25 READINGS CYCLE 28 READINGS CYCLE SCREENS 32 red light 48 relative humidity warnings 25 Repairs 61 Resistance units 31 Resolution 58 RH Set value 29 RH cycle level 58 RH sensor 47 55 RH set point 24 25 RH Set point 29 RS232 cable 56 RS232C 48 screen contrast 48 scroll 52 SENSOR HEAD cleaning 45 Service 60 SET key button 53 SET button 27 Set RH 27 SET SC...

Page 64: ...me Format 27 Tips 42 tissue paper 13 Troble shooting Flashing Display 51 Trouble shooting chemical damage 46 high resistance 45 Hints and Tips 42 large error in calibration curve fit 22 reading too slow 20 thermistor damage 22 variable readings 44 units 55 Units 28 31 Unpacking 8 USB 56 Warnings 7 WARNINGS 25 Warranty 60 washing 45 weather 31 Weight 55 WETTING THE FILTER PAD 13 Windows 8 56 δT 31 ...

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