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West Systems Portable diffuse flux meter Handbook

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Portable diffuse
flux meter
Release 9.1
January 2019

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Summary of Contents for West Systems Portable diffuse flux meter

  • Page 1 Portable diffuse flux meter Release 9.1 January 2019...
  • Page 3 1. The defects are called to the attention of West Systems in writing within one year after the shipping date of the instrument. 2. The instrument has not been maintained, repaired or altered by anyone who was not approved by West Systems.
  • Page 4 The West Systems fluxmeter complies with the requirement of EU directives. conformity information, contact West Systems support@westsystems.com. If your equipment requires maintenance in Italy Before shipping the instrument back to Italy, remember: - When you ask your shipping agent to send the instrument to Italy check that on the Air Waybill the Airport of destination is Pisa.

  • Page 5: Table Of Contents

    Index Introduction ................7 Safety information ............... 7 Preliminary operations ............... 8 Content of the package ..............8 Batteries ..................8 Filters and tubes ................. 8 Backpack ................... 9 Powering On ................9 Warm up ................... 10 Accumulation chamber ..............10 Powering Off ................
  • Page 6 WS-VOC Volatile Organic Compounds detector ......83 11.1 Specifications ................84 11.2 Measuring principle ..............85 11.3 Warm-up ................85 11.4 VOC fluxes measurement ............85 11.5 Calibration check ..............86 11.6 Calibration ................88 11.7 VOC correction factors ............. 93 References ................

  • Page 7: Introduction

    1 Introduction Introduction 1.1 Safety information Carbon dioxide is a toxic gas. Carbon dioxide is colourless, odourless, tasteless and is heavier than air. Air concentration higher than 5000 ppm can cause dizziness, shortness of breath, rapid pulse. Higher concentrations of carbon dioxide can be lethal;...

  • Page 8: Preliminary Operations

    2 Preliminary operations Preliminary operations Read carefully the instructions and the recommendations of the following chapter before proceeding. 2.1 Content of the package The package content may vary depending on the selected configuration. When you first open the package, check the items with the packing list which is attached to the shipping.

  • Page 9: Backpack

    2 Preliminary operations 2.4 Backpack Assemble the fluxmeter on the backback and secure it using the provided knob on the internal side of backpack. 2.5 Powering On Press and hold for about 2 seconds the On/Off button on the external connection panel.

  • Page 10: Warm Up

    2 Preliminary operations Solid blue: the Bluetooth is connected. During this phase it is not visible by other devices. The pump is managed by the instrument and it won’t turn on until a measurement is started by FluxManager software. 2.6 Warm up If your instrument is equipped with a LI-COR LI-830/LI-850 carbon dioxide analyzer: the sensor is temperature-stabilized in order to reduce the interferences due to the gas sample temperature.

  • Page 11: Fluxmanager Software

    3 FluxManager software FluxManager software 3.1 Installation West Systems provides the portable fluxmeter with an Android based mobile device (smartphone / tablet / handheld computer). The Android device is necessary as interface to the portable fluxmeter to manage the measurement, display and store the data.
  • Page 12 3 FluxManager Software...

  • Page 13: Bluetooth Connection

    3 FluxManager software 3.2 Bluetooth connection There is no need to pair the Bluetooth devices before launching the FluxManager app. launch app, FluxManager2 automatically scans available Bluetooth devices in range, for 5 seconds. As soon as one or more portable fluxmeters, accumulation chambers soilboxes...

  • Page 14: Measurement

    3 FluxManager Software 3.3 Measurement Press the START button to start the measurement. The graphical visualization takes place of sensor list. At this point only one sensor at a time is displayed. Switching sensor In case there are more than one sensor with track enabled, only the one in foreground is shown.
  • Page 15 3 FluxManager software Flux data Right cursor Left cursor Regression line Note: the regression is computed on the points included within the left and right cursors. All the other points are ignored by the calculation. The selection of the flux curve interval where to compute the flux is critical and a wrong selection can cause an error on the estimation of the flux.

  • Page 16: Saving A Measurement

    3 FluxManager Software Press the NEXT button to switch sensor 3.4 Saving a measurement Normally a flux measurement requires from 90 up to 480 seconds. The sampling time of a single flux measurement is chosen by the operator on the run. The time usually depends on the extent of the soil flux.
  • Page 17 3 FluxManager software Note: if you press the Start button again without saving, the following screen appears: Press Continue to discard the measurement and go on with a new one. Otherwise press Save to go directly to the saving window. Once the measure is stopped, you can press the Save button to save the measurement.
  • Page 18 3 FluxManager Software Barometric pressure [mBar]: if the accumulation chamber is connected, the field is automatically filled with the value recorded by the barometer placed inside the chamber (average value of the 1 Hz sampling during the measurement). If this value is not available, or if the user prefers to use its own barometer, he can replace the value.
  • Page 19 3 FluxManager software The file name has the following format: [SITE NAME]_[POINT]_[DATE]_[TIME].txt The date is in the format YYYYMMDD The time is in the format HHMMSS For example: site1_3_20180101_183500.txt Backup copy As soon as the user press the Save button, the file is saved in the folder \FluxManager\data, as previously specified.

  • Page 20: Transfer Data To A Pc

    3 FluxManager Software The backup copy has to be created by the user manually, because the FluxManager app is not allowed by the Android operating system to write silently on paths other than the internal memory of the device. If you are not interested to create a second copy of the file, press back and you’ll be redirected to the sampling window where you can start the following measurement.

  • Page 21: Map

    3 FluxManager software 3.6 Map Press the MAP button to enable the visualization of the map. The map is downloaded in real time from the Google Map servers. For this reason the visualization is active only if the Android device has an Internet connection available.

  • Page 22: Preferences

    3 FluxManager Software 3.7 Preferences Pressing the menu icon on the top right corner, the main menu appears. By pressing the menu Sensors, it is possible to enable or disable the chart for each sensor. This setting affects only the on-field visualization: the sensor with chart disabled are sampled and recorded in the same way as the others (one reading per second).
  • Page 23 3 FluxManager software pressing menu Settings, application settings can be visualized and edited: Computation Mode Flux Unit Cleaning Time The Computation mode can be configured as following: 8. Linear regression. This is the standard setting when measuring diffuse degassing. By placing the left and right cursors on the chart, the app shows the value of the linear regression within the selected interval, and the related R...
  • Page 24 3 FluxManager Software The flux unit can be configured as following: 10.ppm/second 11.moles/m /day 12.µmoles/m /second Choose the unit you’re more familiar with. As explained in the following chapter, the ppm/sec represents the “raw data”. Choosing either moles/m /day moles/m /second, the ppm/sec data is converted into flux using the dimensions of the chamber and the environmental parameters.
  • Page 25 3 FluxManager software The menu About show the firmware and software version of the connected devices. Please provide this information when requesting support.

  • Page 26: Measuring Flux

    4 Measuring flux Measuring flux 4.1 Theory of operation In this chapter how to measure the flux and how to interpret the results will be explained. Please refer to chapter 3 to learn about the use of the instrument and the FluxManager software. To better understand the this chapter a basic theory is explained.
  • Page 27 4 Measuring flux soil. A very long recording period is necessary to reach the limit C Soil concentration. In the first part of the flux curve a "sampling line cleaning" area is highlighted: in this area the gas pumped from the accumulation chamber is replacing the gas into the pump, the tubes and the cell detector cell (dead volumes).

  • Page 28: The Measurement

    4 Measuring flux The value of ErrQ can vary in the range from 0 up to 1. Values of ErrQ close to zero (ErrQ < 0.5) means that the regression is not good and that the linear curve computed does not fit the curve. Values of ErrQ close to one (ErrQ >...
  • Page 29 4 Measuring flux The chamber was removed from the soil. The duration of the flux curve recording is normally in the interval 90-240 seconds. Only when measuring very low flux of hydrogen sulphide 300-480 second measurement could be necessary. The following images show a series of common accumulation shapes. The “perfect”...
  • Page 30 4 Measuring flux Gas stratification This shape curve indicates that concentration of the target in air, close to the soil, is very high. This stratification is quite common in case of very high flux combined with a very stable atmosphere. In this case clean the gas line making a measure in air, one meter above the soil surface, and afterwards repeat the flux measurement.
  • Page 31 4 Measuring flux Very low fluxes Of course the noise increases when the flux is very low. No flux The curve is flat and the increase of the gas concentration is very low. Possible causes: 13. There is no flux 14.

  • Page 32: Quantifying The Flux

    4 Measuring flux 4.3 Quantifying the flux As explained in the previous paragraph, the flux is proportional to the concentration increase ratio ppm/sec. The proportionality factor depends on the chamber volume/surface ratio as well as the barometric pressure and the air temperature inside the accumulation chamber.
  • Page 33 4 Measuring flux Method 1: Measuring the slope Set the Accumulation Chamber factor to 1 in order to have the flux measurement expressed in the slope unit "ppm/sec" and translate it in the desired unit with a post processing. Using this method you can focus only on the accumulation chamber interfacing with the soil, the flux curve shape and the other aspects of the measurement, putting off choosing the correct accumulation chamber factor.
  • Page 34 4 Measuring flux Accumulation chamber A factors Volume: 0.00277 m Area: 0.0308 m...
  • Page 35 4 Measuring flux Accumulation chamber B factors Volume: 0.006186 m Area: 0.0317 m...
  • Page 36 4 Measuring flux Accumulation chamber C factors Volume: 0.006878 m Area: 0.0712 m...

  • Page 37: Components

    5 Components Components 5.1 Accumulation chamber The accumulation chamber comes in three different dimensions: Net volume: 0.00277 m Base area: 0.0308 m Internal height: 98 mm Mass: 1.35 Kg (with battery) Net volume: 0.006186 m Base area: 0.0317 m Internal height: 198 mm Mass: 1.55 Kg (with battery)
  • Page 38 5 Components using the type B (height 20 cm) that can cover a very large range of soil flux with a good sensitivity and linearity. The accumulation chamber is the main part of your instrument. The interfacing of the chamber with soil must be performed with great attention. Once the chamber is placed on soil in the measuring site it has to be verified that the rim is placed correctly on soil in order to avoid atmospheric air to enter the chamber.
  • Page 39 5 Components Gas outlet 50 mm PTFE From fluxmeter to chamber filter support On/Off button Charger port Battery box / barometer / thermo- hygrometer Pressure compensation vent Septum Gas Inlet From chamber to fluxmeter Mixing device The chamber internal fan ensures the homogenization of the gas mixture inside the chamber during the flux measurement.
  • Page 40 5 Components Battery charger Connect the provided battery charger to the charger port. Do not switch on the chamber while charging. Use only with the provided internal NiMH rechargeable battery. Do NOT connect the charger if an alkaline battery is inserted. A full recharge takes about 2 hours.
  • Page 41 5 Components Water Trap The tube between the filter and the chamber outlet can be used to install a water trap. Pressure compensation vent The vent is used to maintain pressure equilibrium between inside the chamber and the surrounding air outside the chamber, avoiding the pressurization of the chamber that would alter the gas flow from the soil.

  • Page 42: Pump

    5 Components 5.2 Pump Power supply female panel connector PIN 1: VDC, to positive pole of pump PIN 4: GND, to negative pole of pump Specifications Vacuum: 250 mBar absolute Delivery: 3.1 l/min Power consumption: 150 mA @ 12 Volts Manufacturer: KNF Order model: NMP 830 KNDC Pneumatic fittings diameter: 4 mm...
  • Page 43 5 Components 21.Reassemble the head.

  • Page 44: Fluxmeter Battery

    5 Components 5.3 Fluxmeter battery Nominal voltage: 14.4 V Nominal capacity: 4500 mAh Battery duration: approximately 4 hours. The system is equipped with two interchangeable battery, to guarantee operation during a whole working day. To replace the battery, unplug the battery connector from fluxmeter internal panel and remove the knob as indicated in the picture.

  • Page 45: Fluxmeter Battery Charger

    5 Components 5.4 Fluxmeter battery charger Model: Mascot 2215 Input voltage: 90-264 VAC, 50/60 Hz Max output power: 35 W Trickle charge current: 100mA +/-50mA Leakage current with mains off: < 1 mA Charging time for a single battery: ~ 4 hours Before connecting to the mains, please check that the cord is not damaged.
  • Page 46 5 Components The charger is started by connecting the battery pack to the charger and then connecting the charger to the mains. The LED will be yellow before the fast charge starts and the LED changes to orange. When the batteries are fully charged and the voltage drops because of the -dV signal from the batteries, the charger will go into a top-off charge mode before it goes over to trickle charge mode.

  • Page 47: Backpack

    5 Components 5.5 Backpack If you need to free your self from the backpack and the instrument pull the red belt. Quick release clip 5.6 Tubes Periodically check the status of the tubes and replace them if necessary. Fluxmeter internal tube Internal diameter: 4 mm External diameter: 6 mm Minimum bending radius: 15 mm...
  • Page 48 5 Components Fluxmeter inlet port Fluxmeter outlet port PTFE membrane filter 50 mm...

  • Page 49: Filters

    Please check the status of the filters before each sampling campaign. 5.8 Fittings WEST Systems Tube fitting for 6x4 tubes. The gas sampling line is assembled with 1/8" gas cylindrical or conical thread fittings. The sealing is guaranteed by Loctite 542 dope.

  • Page 50: Calibration Of The Flux Meter

    6 Calibration of the flux meter Calibration of the flux meter The present chapter reports the procedure followed by WEST Systems to check the fluxmeter calibration. The method described refers to carbon dioxide calibration, bu the same procedure is followed for the other gases.

  • Page 51: The Influence Of Pumping Flow

    6 Calibration of the flux meter 6.2 The influence of pumping flow We have carried out some sets of measures utilizing the same injected flux but with different pumping flow from the accumulation chamber to the detector. The pumping flow was changed by means of a mechanical flow reducer and measured with an Alicat Mass flow meter.

  • Page 52: Influence Of The Mixing Device Rotation Speed

    6 Calibration of the flux meter 6.3 Influence of the mixing device rotation speed The following plot shows the measured flux vs the mixing device rotation speed. Battery status vs RPM. The following plot shows the mixing device RPM (Rotation per minute) vs power supply voltage.

  • Page 53: Fluxrevision

    7 FluxRevision FluxRevision FluxRevision is the software that allows to quickly elaborate a large number of files created by FluxManager. Note: FluxRevision runs on Microsoft Windows operating systems; the Microsoft .NET framework is required on the machine. To download the files from the Android device to the PC, follow the instructions reported on chapter 2.
  • Page 54 7 FluxRevision If some files are missing environmental parameters, you'll see the window appear. The volume of the accumulation chamber is obtained with the type of chamber (e.g. A, B, C) that you inserted in the FluxManager software. Check that the information about the chamber type (A in the illustration) is correct: the displayed type is the one obtained from the files.
  • Page 55 7 FluxRevision To set the barometric pressure or the temperature in the measures that are missing this parameter, replace the default values (1013 mBar and 20°C) and press OK. If the “Apply to all analysis” box is checked, the parameters in the measures that already had them will be overwritten.
  • Page 56 7 FluxRevision Selecting an item in the list or pressing one of the navigate buttons, the flux curves are displayed. Like in FluxManager, are displayed the graphs of the sensors with TRACK=ON. They are usually the gas sensors.
  • Page 57 7 FluxRevision Scaling panel Auto: resets the image to the automatic scale View all: sets the axis limits to the minimum and maximum recorded Regression panel values The Slope, Flux and ErrQ parameters Custom: clicking on the button, are initially filled with the result of the mouse pointer becomes a the regression computed on the field.

  • Page 58: Report File

    7 FluxRevision Auto Best Slope / Auto Best ErrQ / Auto Best Product: see the Auto Regression function in the previous paragraph. In this case the automatic regression is carried out only in the selected file. Save as JPEG: exports the graph image to a file.
  • Page 59 7 FluxRevision SOIL TEMPERATURE [°C] SOIL RELATIVE HUMIDITY (%) ACCUMULATION CHAMBER SENSOR_ID: LLIMIT [sec] SENSOR_ID: RLIMIT [sec] SENSOR_ID: LCONC [ppm] SENSOR_ID: RCONC [ppm] SENSOR_ID: SLOPE [ppm/s] SENSOR_ID: FLUX [mol/m2/day] SENSOR_ID: R2 FILENAME The report file is a text file, the fields are separated by the TAB character, so the file can be easily opened with a spreadsheet editor (e.g.

  • Page 60: Li-Cor Carbon Dioxide Detector

    8 LI-COR Carbon dioxide detector LI-COR Carbon dioxide detector The information discussed in this chapter applies to the carbon dioxide detector model LI-COR LI-830 or LI-850. For full specifications and instructions please refer to the LI-COR manual which is attached to this handbook. 8.1 Calibration check As explained previously in Chapter 4, the flux measurement is proportional to the slope of the concentration curve versus time.

  • Page 61: Calibration

    8 LI-COR Carbon dioxide detector 8.2 Calibration What you need to calibrate the detector 28.A laptop/personal computer running Microsoft Windows operating system; 29.An USB/RS232 adapter; 30.A null modem RS232 cable, connectors DB9 female to DB9 female. The cable is furnished in the detector package; 31.A cylinder of nitrogen or synthetic air, or a SODA LIME trap or a DRAGER PIPE to trap the carbon dioxide.
  • Page 62 8 LI-COR Carbon dioxide detector Run the LICOR windows application on your Windows laptop; Press File-Connect. You’ll be asked to input the serial port which corresponds to the USB-RS232 adapter (COM1 in the previous example). Set the sampling frequency to 1 Hz. The application shows the current concentration reading as well as the cell temperature and pressure.
  • Page 63 8 LI-COR Carbon dioxide detector Tedlar sampling bag RS232 null modem cable (to laptop) Wait for the CO2 concentration to get stable and press the button Zero. Wait for a few seconds until the operation is completed. Remove the sampling bag from the inlet port. Fill the “span”...

  • Page 64: Ws-Ch4-Tld Methane Detector

    In the best case, it will be necessary to send the instrument to West Systems for a cleaning, which is a long and expensive procedure. Never open the protective case of the WS-CH4-TLD. Some components like the optical fiber could be damaged if touched or moved.

  • Page 65: Detector Specifications

    9 WS-CH4-TLD Methane detector The RS485 cable provides both power supply and communication 9.1 Detector specifications Resolution: 0.1 ppm Concentration measurement range: from 0.1 ppm to 10% vol* Accuracy: ±10% Operating temperature: -10°C...+45°C Selectivity to methane Flux Measurement range: from 1 to 900,000 millimoles/m2 per day Range Unit Precision...
  • Page 66 9 WS-CH4-TLD Methane detector The following plot (ppm vs. seconds) shows a stability test while injecting atmospheric air for about 1,000 seconds. The plot (ppm vs. seconds) shows an accumulation curve while measuring a flux of 1.7 mmoles/m2 per day...

  • Page 67: Computing Flux

    9 WS-CH4-TLD Methane detector In order to guarantee the measuring of CH4 concentration in a wide range (0- 100% vol), the sensor needs to apply different settings on the laser diode.This adaptations produce a gap of a few seconds during which a valid concentration value is not available.
  • Page 68 9 WS-CH4-TLD Methane detector If you cross that threshold during the accumulation curve, please apply the interpolation on the second part of the curve. Do not include the ten-seconds gap into the linear regression in order to prevent measure errors. Extend the duration of the accumulation curve if necessary.

  • Page 69: Calibration

    Each time a measurement campaign is initiated the instrumental response of the gas sensors must be verified. If the error is not acceptable, the instrument has to be sent to West Systems for calibration. To simplify the explanation see the following example.

  • Page 70: Ws-Tox-H2S Hydrogen Sulfide Detector

    10 WS-TOX-H2S Hydrogen sulfide detector WS-TOX-H2S Hydrogen sulfide detector Signal Legend +VDC Gnd: Ground reference for power supply and RS485 +VDC: 10-28 Volts Power supply input RS485-B RS485-A: Digital signal output A RS485-A RS485-B: Digital signal output B +12V RS485-B Sensor specifications Ambient conditions: Air temperature -30°C to 50 °C...
  • Page 71 10 WS-TOX-H2S Hydrogen sulfide detector Cross sensitivity Unfortunately, the hydrogen sulfide detector is affected by cross sensitivity with several gas species. In the table below these cross sensitivity are reported: Test @ ppm Reading ppm Sulfur Dioxide < 2 Nytrogen monoxide <...

  • Page 72: Calibration

    10 WS-TOX-H2S Hydrogen sulfide detector 10.1 Calibration Check the calibration using the same procedure explained in chapter 8.1. We recommend the use of Tedlar sampling bags for injecting the calibration mixures. For the check of the zero, a bottle of Nitrogen or synthetic air can be used. For the check of the span, you can use a mixture containing between 10 and 25 ppm.
  • Page 73 10 WS-TOX-H2S Hydrogen sulfide detector 5) Once connected, the app shows all the available sensors. Tap on the H S detector to start the calibration. 6) Warning: as soon so the calibration starts, the calibration parameters stored in the H S detector will be reset to fabric default.
  • Page 74 10 WS-TOX-H2S Hydrogen sulfide detector 8) Connect the zero gas Tedlar bag to the fluxmeter inlet. Wait for the reading to get stable. 9) When the signal is finally stable, select the interval by tapping on the screen. The average and standard deviation of the selected period is shown on the display.
  • Page 75 10 WS-TOX-H2S Hydrogen sulfide detector Connect the span gas Tedlar bag to the fluxmeter inlet. The gas concentration should start increasing. Wait for the reading to get stable. In the example, the H S concentration of the span gas mixtures is 25 ppm. 11) When the signal is finally stable, select the interval by tapping on the screen.
  • Page 76 10 WS-TOX-H2S Hydrogen sulfide detector 12) In the final screen, the app shows the average values that were selected for the zero and span gas mixtures. Input the H S concentration in ppm of the span calibration mixures example). Press the CALIBRATE button to apply the calibration to the sensor.

  • Page 77: Replacing The Sensor Head

    10 WS-TOX-H2S Hydrogen sulfide detector 10.2 Replacing the sensor head...
  • Page 78 10 WS-TOX-H2S Hydrogen sulfide detector Now install the new sensor head (WS-H2S-BH Head) and re-assemble the detector. Please check the O-Ring status and check the sealing of the sensor head/on line adapter. After changing the head, a recalibration of the detector is necessary.

  • Page 79: Flux Measurement

    10 WS-TOX-H2S Hydrogen sulfide detector 10.3 Flux measurement S fluxes from soil are simulated by injecting a known flow of gas into the accumulation chamber. The interface between the accumulation chamber and the calibration table is built to minimize the gas leakage. For flux between 0.0002 and 0.02 moles/m /day the injected flux is controlled and measured with a precision mass flow controller.
  • Page 80 10 WS-TOX-H2S Hydrogen sulfide detector The simulated flux experiment was done using the accumulation chamber B that's more accurate for the hydrogen sulfide measurement. Room temperature: Between 20.2 and 21.4 °C Air relative humidity 52-54% Barometric pressure between 1013.1 and 1013.8 HPa Accumulation Chamber B constant at 1013 and 20°C: 0.707 (moles/m /day)/(ppm/sec)
  • Page 81 10 WS-TOX-H2S Hydrogen sulfide detector In the plot below a typical hydrogen sulfide flux curve: the slope is 0.028 ppm/sec and the flux is 0.019 moles/sm/day In the plot below the "base line" of the hydrogen sulfide detector output is reported.
  • Page 82 10 WS-TOX-H2S Hydrogen sulfide detector In the plot below the stability of the hydrogen sulfide detector output is reported. The injected gas mixture at 1 liter per minute was 20 ppm of H2S in nitrogen.

  • Page 83: Ws-Voc Volatile Organic Compounds Detector

    11 WS-VOC Volatile Organic Compounds detector WS-VOC Volatile Organic Compounds detector Power supply and RS-485 The connector provides both power supply and the communication lines to the sensor. The cable pinout is shown in the following table: Signal Legend Gnd: Ground reference for power supply and RS485 +VDC +VDC: 10-28 Volts Power supply input +VDC...

  • Page 84: Specifications

    11 WS-VOC Volatile Organic Compounds detector O-Ring gasket PID Detector Temperature, pressure and RH sensors board 11.1 Specifications VOC Measurement range: 0…50 ppm Isobutylene Detection limit: 1 ppb Isobutylene Operating temperature range: from -40 to +55 °C Temperature, relative humidity and pressure sensors are installed inside the measurement cell.

  • Page 85: Measuring Principle

    11 WS-VOC Volatile Organic Compounds detector 11.2 Measuring principle Volatile organic compounds (VOC) are a large family of carbon-containing compounds which are emitted into the atmosphere from a variety of industrial processes. They are commonly found as a vapor at room temperature. The WS-VOC sensor allows the measurement of such compounds by using a PID (Photo-Ionization Detector), equipped with a Krypton lamp at 10.6 eV.

  • Page 86: Calibration Check

    11 WS-VOC Volatile Organic Compounds detector since it makes up for a contribution which has a different origin than the one which is usually inspected. 3) In presence of a real VOC soil emission, the VOC concentration increases in a linear or exponential shape during the whole measurement, following the theory of the accumulation chamber method (see chapter 4.1).
  • Page 87 11 WS-VOC Volatile Organic Compounds detector The most important aspect to understand is that the flux is proportional to the gradient of concentration over time: ppm/second. This aspect allows us to simplify the control of the response of the gas analyzers. Each time a measurement campaign is initiated the instrumental response of the gas sensors must be verified and, if necessary, their calibration fine-tuned.

  • Page 88: Calibration

    11 WS-VOC Volatile Organic Compounds detector The detector has significantly lost sensitivity. The sensor baseline presents drifts, even after the warm-up. The sensor reading is not stable. If one of the following cases occurs, the sensor needs to be sent back to the factory for maintenance.
  • Page 89 11 WS-VOC Volatile Organic Compounds detector Once connected, the app shows all the available sensors. Tap on the VOC detector to start the calibration. 6) Warning: as soon so the calibration starts, the calibration parameters stored in the VOC detector will be reset to fabric default.
  • Page 90 11 WS-VOC Volatile Organic Compounds detector 8) Connect the zero gas Tedlar bag to the fluxmeter inlet. Wait for the reading to get stable. 9) When the signal is finally stable, select the interval by tapping on the screen. The average and standard deviation of the selected period is shown on the display.
  • Page 91 11 WS-VOC Volatile Organic Compounds detector Connect the span gas Tedlar bag to the fluxmeter inlet. The gas concentration should start increasing. Wait for the reading to get stable. example, isobutylene concentration of the span gas mixtures is 25 ppm. 11) When the signal is finally stable, select the interval by tapping on the screen.
  • Page 92 11 WS-VOC Volatile Organic Compounds detector 12) In the final screen, the app shows the average values that were selected for the zero and span gas mixtures. Input the concentration in ppm of the span calibration mixtures (25 in the example). Press the CALIBRATE button to apply the calibration to the sensor.

  • Page 93: Voc Correction Factors

    11 WS-VOC Volatile Organic Compounds detector 11.7 VOC correction factors The sensitivity of the PID varies according to the type of lamp and the VOC species which are present in the sample. The table included at the end of the paragraph shows the ionizing energy (IE) and the response factor (RF), for the most common volatile organic compounds.
  • Page 94 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Acetaldehyde 10.23 Bromoacetylene 10.31 Acetamide 9.69 Bromobenzene 8.98 0.32 Bromobutane, 1- 10.13 Acetic acid 10.66 Acetic anhydride 10.14 Bromobutane, 2- 10.01 0.97 Bromocyclohexane 9.87 Acetoin ~9.8 Acetone 9.69 1.17 Bromoethane 10.29...
  • Page 95 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Butylamine, sec- 8.70 Cresol, o- 8.14 Butylamine, tert- 8.64 Cresol, p- 8.31 Butylbenzene 8.69 Cresyl acetate, p- 8.60 Butylbenzene, sec- 8.68 Cresyl ethyl ether, p- Butylbenzene, tert- 8.69 Cresyl methyl ether Butylene carbonate, 1,2- ~10.4...
  • Page 96 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Dichlorobenzene, p- 9.06 Dimethylacetamide N,N- 8.81 Dichloroethene, 1,1- 10.00 Dimethylacetylene 9.58 Dichloroethene, 1,2- 9.65 Dimethylamine 8.24 Dichloroethene, cis-1,2- 9.66 Dimethylaminoethanol, 2- 8.80 Dichloroethene, trans-1,2- 9.65 Dimethylaniline, NN- 7.12 Dichloromethane 11.32 Dimethylboron bromide...
  • Page 97 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Ethyl acetate 10.01 Furfuryl mercaptan Ethyl acetoacetate ~9.5 Gasoline ~9.9 Geranial Ethyl acrylate 10.3 Geraniol Ethyl benzoate Geranyl acetate Ethyl butyrate ~9.9 Germane 11.34 Ethyl chloroformate 10.64 Glutaraldehyde ~9.6 Ethyl cyanoacrylate Glycidyl methacrylate...
  • Page 98 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Iodomethane 9.54 Linalool oxide Isoalkanes, C10-C13 ~9.6 Linalyl acetate Isoamyl acetate ~9.7 Maleic anhydride Isoamyl salicylate Mandelic acid Isoamylene 8.69 0.82 Menthol Isobornyl acetate Menthone Isobutane 10.57 Mercaptoacetic acid ~9.8 Isobutanol 10.12...
  • Page 99 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Methyl thioglyconate Nonene (mixed isomers) ~9.3 Methyl undecanal, 2- Nonene, 1- ~9.4 Norbornadiene, 2,5- 8.38 Methyl vinyl ketone 9.65 Methyl-1-butene, 3- 9.51 Ocimene 8.60 Octachloronaphthalene Methyl-2-butanol, 3- 9.88 Methyl-2-hexenoic acid, trans-3- Octamethylcyclotetrasiloxane Methyl-2-propen-1-ol, 2-...
  • Page 100 11 WS-VOC Volatile Organic Compounds detector Chemical name Chemical name [eV] [eV] Pinene, α- 8.07 0.34 Tert-butyl formate 10.52 Pinene, β- 8.10 Tetrabromoethane, 1,1,2,2- Piperazine 8.72 Tetracarbonylnickel 8.28 Piperidine 8.03 Tetrachloroethylene 9.33 Piperylene 8.60 Tetrachloronaphthalene, 1,2,3,4- Prop-2-yn-1-ol 10.50 Tetrachloropyridine, 2,3,5,6- Propadiene 9.83 Tetraethyl orthosilicate...
  • Page 101 11 WS-VOC Volatile Organic Compounds detector Chemical name [eV] Trimethylbenzene mixtures 8.41 Trimethylbenzene, 1,3,5- 8.39 Trimethylcyclohexane, 1,2,4- 9.35 Trimethylene oxide 9.65 Trimethylsilane Trioxane 10.3 Turpentine ~8.5 Turpentine oil TVOC Undecane 9.56 Vanillin Vinyl acetate 9.19 Vinyl bromide Vinyl chloride 9.99 Vinyl ethyl ether 8.98 Vinyl fluoride...

  • Page 102: References

    12 References References If you'd like to have your paper(s) reported here please send us the paper abstract and we'll include it in the next releases. Thanks. Monitoraggio del flusso di biogas diffuso dal suolo da discariche RSU:Il caso di Legoli, Peccioli (PI).
  • Page 103 12 References Spatial and temporal variations of diffuse CO2 degassing at Santa Ana- Izalco- Coatepeque volcanic complex, El Salvador, Central America, Salazar J.M.L., Hernández P.A., Pérez N.M., Olmos R., Barahona F., Cartagena R., Soriano T., Lopez K., and Notsu K. ,Bulletin Geological Society of America, Volumen 375, 135-146, 2004.
  • Page 104 © www.westsystems.com Portable soil flux meter handbook Release 9.1 January 2019...

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