METER GROUP WP4C Operator's Manual
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METER GROUP WP4C Operator's Manual

Wp4c dew point potentiameter
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WP4C
Dew Point PotentiaMeter
Operator's Manual
Distributed & Supported By:
www.edaphic.com.au
info@edaphic.com.au
Ph: 1300 430 928

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Summary of Contents for METER GROUP WP4C

  • Page 1 WP4C Dew Point PotentiaMeter Operator’s Manual Distributed & Supported By: www.edaphic.com.au info@edaphic.com.au Ph: 1300 430 928...
  • Page 2 WP4C METER Group, Inc. 2365 NE Hopkins Court Pullman WA 99163 Phone: 509-332-5600 Fax: 509-332-5158 Website: www.metergroup.com Email: support.environment@metergroup.com or sales.environment@metergroup.com Trademarks c 2017 METER Group, Inc. All Rights Reserved...

  • Page 3: Table Of Contents

    2.2 WP4C and Water Potential ....2.3 How the WP4C works ....
  • Page 4 6.6 Taking a Reading ..... 25 6.7 How WP4C takes Readings ....25 7 Computer Interface 7.1 AquaLink 4 Software .

  • Page 5: Introduction

    1 INTRODUCTION Introduction Welcome to METER’s WP4C Dew Point PotentiaMeter, the research standard for measuring water potential. WP4C is the fastest, most accurate, and most reliable instrument available for measuring water potential using the chilled-mirror dew point technique. The WP4C suits the needs of the scientist and student.

  • Page 6: About This Manual

    This manual includes instructions for setting up, calibrating, and maintaining the WP4C. Please read these instructions before operating WP4C to ensure that the instrument performs to its full potential. This manual will aid end users in understanding the basic concepts of water potential and enable them to use our instrument with confidence.
  • Page 7 WP4C 1 INTRODUCTION for which the same may be employed. The use of this equipment con- stitutes Buyer’s acceptance of the terms set forth in this warranty. There are no understandings, representations, or warranties of any kind, express, implied, statutory or otherwise (including, but with- out limitation, the implied warranties of merchantability and fitness...

  • Page 8: About The Wp4C

    Interface Cable: Standard RS232 to USB cable (included) Compatible Standards: ASTM D6836-07 Warranty: One year parts and labor The WP4C (and all vapor pressure instruments) are limited by accuracy in the wet end of the water potential range. The range of 0 to 5 MPa has an accuracy of 0.05 MPa.

  • Page 9: Wp4C And Water Potential

    At equilibrium, the water potential of the air in the chamber is the same as the water potential of the sample. In the WP4C, the mir- ror temperature is precisely controlled by a thermoelectric (Peltier) cooler.

  • Page 10: Wp4C And Temperature

    2 ABOUT THE WP4C WP4C WP4C and Temperature Large temperature differences, between sample and block, will cause longer reading times, since a complete and accurate reading will not be made until the difference between the sample temperature and the block temperature is less than 1.0 degree. To help you monitor the temperature difference between your sample and the block, you...

  • Page 11: Getting Started

    To protect the internal electrical components, and to avoid inaccurate readings, place your WP4C in a location where the temperature remains fairly stable. This location should be well away from air conditioner and heater vents, open windows, outside doors, refrigerator exhausts, or other items that may cause rapid temperature fluctuation.

  • Page 12: Features

    Figure 2: Back View of WP4C Preparing the WP4C for Operation After finding a good location for your WP4C, plug the power cord into the back of the unit. Before turning it on, pull open the sample drawer (turn the knob to the OPEN/LOAD position). You usually...

  • Page 13: Portability

    Remove this sample cup and turn the instrument on. The ON/OFF switch is located on the lower right corner of the WP4C back panel. The model and then the main menu will appear on the LCD.
  • Page 14 3 GETTING STARTED WP4C 2. Place the WP4C on a level surface. Care should be taken to minimize temperature gradients that may affect the instrument while in the field. A Styrofoam box, for example, will help minimize temperature effects. 3. Plug the 12-volt inverter to the 12-volt output of the vehicle, or directly to the battery itself.

  • Page 15: The Menus

    4 THE MENUS The Menus The Main Menu Every time you turn on your WP4C, it will open to this screen. If this screen does not appear, refer to Chapter 12 for troubleshooting instructions. The water potential and sample temperature displays on the screen.

  • Page 16: Reading Modes

    4.1.2 Reading Modes Precise Mode When you first turn on the WP4C, it will be in precise mode. The WP4C repeats sample measurements until successive readings agree within a preset tolerance (0.03 MPa for Ψ > 40 MPa; otherwise 0.3 MPa).
  • Page 17 > MPa. In this mode the WP4C will measure the sample, stop to dis- play the water potential and sample temperature, then begin another read cycle.

  • Page 18: System Configuration

    Figure 6: System Configuration Menu Changing the Beeper When you are reading, the WP4C has two ways of notifying you when it completes the water potential reading for your sample. It will notify you with the beeper he beeper and a flashing green LED,...
  • Page 19 WP4C 4 THE MENUS located on the left front corner of the WP4C case. In fast and pre- cise reading modes, the LED will flash once when a sample is started. When it is finished the LED will flash continuously until the knob is moved to the OPEN/LOAD position (if not operating in continuous mode).
  • Page 20 4 THE MENUS WP4C The WP4C gives you the ability to manually set your instrument sample chamber temperature. To set your instrument sample cham- ber temperature, press the lower right button next to the “set T” in the System Con guration menu.

  • Page 21: Sample Equilibration Screen

    Sample Equilibration Screen To see the temperature difference between your sample and the WP4C, press the lower right button at the main menu. You can only access the Temperature Difference screen when the drawer knob is in the OPEN/LOAD position.
  • Page 22 4 THE MENUS WP4C Note:) It is important that Ts Tb is negative in order to prevent condensation inside the sample chamber.

  • Page 23: Calibration And Verification

    When to Verify Calibration The calibration of your WP4C should be checked with the KCl stan- dard before each use. It can also be checked by measuring distilled water, but this is often not a good choice for checking calibration.

  • Page 24: How To Verify And Calibrate The Wp4C

    Empty the whole vial of KCl solution into a sample cup and place it in the WP4C sample drawer. Make sure you calibrate using the same type of sample cup (plastic or stainless steel) that you will make subsequent measurements with.
  • Page 25 2.19 MPa. At 25 C this should be 2.22 MPa. If your WP4C is reading within 0.05 MPa of the KCl solution, press Exit and proceed with reading. If it is not, a change in calibration may have occurred, or the sensor chamber may be contaminated.

  • Page 26: Sample Preparation

    Finally, if you calibrate the WP4C (see chapter 5), be sure to calibrate using the same type of sample cup that you intend to use for subsequent measurements.

  • Page 27: Dry Samples

    For example, if you were measuring a dry sample and the following screen appeared: This screen indicates that the last water potential reading the WP4C measured on this sample was 301.8 Megapascals. Therefore, the ac- tual water potential of the sample is lower than the instrument can...

  • Page 28: Samples And Temperature

    For samples that are more than 1 C below chamber temperature, the WP4C waits until their temperature increases to 1 C below chamber tem- perature to start a reading.

  • Page 29: Measuring Plant Samples

    6 SAMPLE PREPARATION Measuring Plant Samples The WP4C can be used to measure the water potential of leaves and plant material. Please refer to the application note: Measure- ment of Leaf Water Potential Using the WP4, which can be found at www.metergroup.com.
  • Page 30 6 SAMPLE PREPARATION WP4C Cautions Never leave a sample in your WP4C after a reading has finished. The sample may spill and contaminate the instrument chamber if the instrument is accidentally moved or jolted. Never try to move your instrument after loading a sam- ple.

  • Page 31: Computer Interface

    7 COMPUTER INTERFACE Computer Interface Your WP4C comes with a RS-232 to USB Serial cable. Using this cable, you can connect to your WP4C and send water activity data to a computer for further analysis and storage. The interface is run through the AquaLink 4 Software or a terminal communication pro- gram.

  • Page 32: Using A Communication Program

    Internet and Hyperterminal which came standard with Windows prior to Windows 7. To use any of these terminal programs with your WP4C, follow the instructions for the program with the following settings. Be sure to power on the WP4C prior to connecting the USB interface cable to your computer.
  • Page 33 1 stop bit Flow control set to none After successfully connecting the WP4C to your computer and upon completion of a water activity reading, the data will be displayed in the terminal program in the format as follows: measurement time (minutes), sample temperature, and water potential (in both Mega- Pascals and pF).

  • Page 34: Theory: Water Potential

    Pressure potential depends on the hydrostatic or pneumatic pressure on the water. The WP4C measures the sum of the osmotic and matric potentials in a sample. Often one or the other of these potentials will be the domi- nant factor in determining the total potential.

  • Page 35: Effect Of Temperature On Water Potential

    8 THEORY: WATER POTENTIAL of a closed chamber, then measuring the vapor pressure of that headspace. In the WP4C, a sample is placed in a sample cup, which is sealed against a sensor block. Inside the sensor block is a fan, a dew point sensor, a temperature sensor, and an infrared thermome- ter.

  • Page 36: Estimating Osmotic Potential

    Estimating Osmotic Potential The WP4C measures the sum of osmotic and matric potential. An approximate value for the osmotic potential can be found by mea- suring the electrical conductivity (EC) of the saturation extract of the soil.

  • Page 37: Cleaning And Maintenance

    WP4C 9 CLEANING AND MAINTENANCE Cleaning and Maintenance The accuracy of your WP4C is vitally dependent on keeping your instrument clean. Dust and sample debris can contaminate the sam- pling chamber and must therefore be regularly cleaned out. To clean your instrument, carefully follow these instructions.

  • Page 38: Cleaning Procedure

    WP4C Figure 10: View of Inside Block Cleaning Procedure Cleaning your WP4C is a multi-step procedure which involves wash- ing, rinsing, and drying for each specific area as outlined below: 1. Cleaning the Inside Chamber Note: Be extremely careful not to damage the fan blades in the chamber.
  • Page 39 WP4C 9 CLEANING AND MAINTENANCE of IPA or cleaning solution (the IPA or cleaning solution will become contaminated). (c) WASH–Clean all surface edges of the samples chamber in- cluding the edge where the sample cup seals to the cham- ber block. You may need to replace the Kimwipe if it becomes too dirty during this process.
  • Page 40 20-pin plug on the block. Lock it in place with the locking levers. (d) Screw the thumb-screws on the block back in until they are hand-tight. (e) Replace the case lid and secure the lid screw. 6. Connect the WP4C power cord.

  • Page 41: Checking Calibration

    9 CLEANING AND MAINTENANCE Checking Calibration After you have cleaned the chamber and other parts of your WP4C, it is important to check the instrument performance in order to correct for any calibration change that may have occurred during cleaning procedures.

  • Page 42: Repair Instructions

    WP4C Repair Instructions If your WP4C ever needs to be sent in for service or repair, call ME- TER at 509-332-5600 or fax us at 509-332-5158. We will ask you for your address, phone number, and serial number. For non-warranty repairs, we will also ask for a payment method (such as a purchase order or credit card number), a repair budget, and billing address.

  • Page 43: Repair Costs

    WP4C 10 REPAIR INSTRUCTIONS 3. Do not ship your WP4C to us with the power cord; we have plenty here to use with your instrument, and it may damage the instrument in shipment. 4. Please review the RMA form and verify the ship to and bill to information, contact name, and problem description.

  • Page 44: Troubleshooting

    11 TROUBLESHOOTING WP4C Troubleshooting WP4C is a high performance instrument, designed to have low main- tenance and few problems if used with care. Unfortunately, some- times even the best operators using the best instruments encounter technical difficulties. Here is a list of some problems that may oc- cur.
  • Page 45 WP4C 11 TROUBLESHOOTING Check to make sure your power cord is securely attached to the back of the instrument and the power outlet. A power sure may have caused a fuse to blow. Follow steps 1 through 5 to change the fuses.
  • Page 46 11 TROUBLESHOOTING WP4C fan blade. This is especially likely if you have just cleaned the chamber. If you suspect this may have happened, contact METER for details on replacement. 3. PROBLEM: Water potential readings on KCl standards are too high or low and a calibration adjustment cannot be made any higher or lower.
  • Page 47 The mirror needs to be cleaned, along with the rest of the sample chamber, until it disappears. This triangle is a mirror performance indicator. When the WP4C senses that the mirror performance has dropped to unacceptable levels, it will display the triangular warning sign after measuring the sample.

  • Page 48: Sensor Performance Screen

    7. PROBLEM: The “Set T” option does not appear anymore in the WP4C System Configuration menu. SOLUTION: The temperature control module inside the WP4C is broken or not functioning correctly.
  • Page 49 WP4C 11 TROUBLESHOOTING The Performance Evaluation screen gives you four values. The top left value is the value the thermocouple is reading. It is basically the difference in temperature between the block and the mirror. If this is zero, there is something wrong with the thermocouple. The top right value is the value read by the thermopile, which is the temper- ature difference between the block and what it “sees”...

  • Page 50: Further Reading

    Soil Science Society of America. Madison, Wisconsin. pp. 1-22. 12.1 Application Notes The following WP4C application notes are available from METER by request and from our website under the education tab, choose WP4C. Generating a Soil Moisture Characteristic with the WP4C.
  • Page 51 WP4C 12 FURTHER READING Classification of Expansive Soils using the WP4C Dew point PotentiaMeter...

  • Page 52: Preparing Salt Solutions

    13 APPENDIX A WP4C Appendix A 13.1 Preparing Salt Solutions Following is a table showing the water potential at given concentra- tions of NaCl and KCl at 20 C. Table 2: Water Potential of NaCl and KCl in Megapascals (MPa)

  • Page 53: Appendix B

    WP4C 14 APPENDIX B Appendix B Temperature Correction of METER’s Verification Standards Table 3: Water Activity of Selected Salt Solutions 0.50 2.33 6.00 8.57 13.41 17.18 Temp. mol/kg mol/kg mol/kg mol/kg mol/kg mol/kg ( C) NaCL NaCL LiCl LiCl LiCl 15.0...

  • Page 54: Declaration Of Conformity

    2010 This is to certify that the Dew Point PotentiaMeter, manufactured by METER Group, Inc., a corporation based in Pullman, Washington, USA meets or exceeds the standards for CE compliance as per the Council Directives noted above. All instruments are built at the factory at METER and pertinent testing documentation is freely available for verification.

  • Page 55: Certificate Of Traceability

    Pullman WA 99163 USA Tel: 509-332-5600 Fax: 509-332-5158 support.environment@metergroup.com This NIST seal certifies that METER Group, Inc. manufactures all WP4C Dew Point PotentiaMeters according to temperature stan- dards with calibration traceable to the National Institute of Stan- dards and Technology (NIST).
  • Page 56 Index Accessories, 7 Declaration of Conformity, 50 Application Notes, 46 Dirty Mirror Indicator, 26 AquaLink 4 Software, 27 Distilled Water, 19 Dry Samples, 23, 42 Beeper, 14, 44 Dry Water Potential, 23 Block Failure, 40, 43 Block Sensors, 33 Email, 1, 51 Buttons Error Messages, 40 Menu Selection, 11...
  • Page 57 WP4C INDEX Spanish, 11 How WP4C Takes, 25 Swedish, 11 Taking Readings, 25 Leaf References, 46 Measuring Water Potential in Repair Continuous Mode, 13 Costs, 39 LED, 14, 44 Instructions, 38 Linear Offset Shipping, 38 Adjusting for, 20 Sample Loaner Service, 39...
  • Page 58 Water Potential, 30 Definition, 5 Displayed, 8 Equation, 30 Measurement, 30 Theory, 30 WP4C and Temperature, 6 Chilled Mirror Dew Point Tech- nique, 5 Important Tips, 16 Measuring Water Potential, 30 Preparing for Operation, 8 Theory, 30 WP4C Readings Cautions, 26...

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