INSTRUCTION MANUAL DMM600 Duff Moisture Meter 5/02 C o p y r i g h t ( c ) 2 0 0 2 C a m p b e l l S c i e n t i f i c , I n c .
Warranty and Assistance The DMM600 DUFF MOISTURE METER is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
DMM600 Table of Contents PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections. 1. Introduction.................................................................1 1.1 DMM600 Packing List .............................................................................2 2. Specifications .............................................................2 3. Description of DMM600 .........................................
DMM600 Table of Contents 7. Maintenance ..............................................................12 7.1 Changing the 9-Volt Battery .................................................................. 12 8. Drying Samples and Calculating Volumetric Water Content ......................................................12 8.1 Conventional Oven Method ................................................................... 12 8.2 Microwave Oven Method..............................................................
DMM600 Duff Moisture Meter 1. Introduction The DMM600 Duff Moisture Meter is the product of collaboration between Campbell Scientific, Inc. and USDA-Forest Service, Rocky Mountain Research Station and Missoula Technology and Development Center. The DMM600 measures volumetric water content of organic forest floor material. It is a portable, battery-powered device that uses measurement methods that are sensitive to the dielectric permittivity of the material being measured.
DMM600 Duff Moisture Meter 1.1 DMM600 Packing List The following are included with the DMM600: 1. Carrying case. 2. CD containing (a) video instruction, (b) PCDMM software, (c) DMM600 operating manual, and (d) a sample Excel spreadsheet for calibrations. 3. 3 inch (7.5 cm) diameter # 4 sieve. 4. 6 foot, 9-conductor cable for serial communications between DMM600 and PCTDR. 5. Screwdriver. 6. Spare 9 volt battery. 2. Specifications Physical Dimensions: 3.5" diameter, 10" length Weight: 3.7 lb.
DMM600 Duff Moisture Meter FIGURE 1. DMM600 3.1 Sample Chamber The sample chamber holds the sample during measurement. The sample chamber is accessed by loosening the chamber access thumbscrew, rotating the sample chamber cap slightly counter-clockwise and lifting the cap away from the sample chamber. A piston located inside the cap is attached to the compression knob by a threaded shaft. With the sample in the sample chamber, the compression knob is turned to compress the sample for measurement.
DMM600 Duff Moisture Meter 3.3 Display End 3.3.1 Power Switch A toggle switch turns the DMM600 on and off. A single beep sounds when the DMM600 is turned on. To conserve battery power, the DMM600 will automatically turn off after about 5 minutes of inactivity. If the DMM600 is in the power-saving mode, toggling the power switch or compressing the sample will restore measurement mode. 3.3.2 Audible Indicator The audible indicator uses a port to the side of the power switch. 3.3.
DMM600 Duff Moisture Meter 4. Discussion of Water Content Measurement with DMM600 4.1 Discussion of Gravimetric and Volumetric Water Content The DMM600 is sensitive to water content on a volume basis, i.e. volumetric water content. Volumetric water content is the volume of water in a given volume of material. Gravimetric water content is a weight-basis parameter and is the ratio of the mass of water to the mass of the material with no water.
DMM600 Duff Moisture Meter FIGURE 2. Downloading coefficients to convert to gravimetric water content for above example. 4.1.1 Determining Duff Sample Bulk Density The bulk density of the sample at time of measurement is determined as follows. 1. After the measurement is made, count the number of compression knob rotations required to move compression piston from measurement position to completely out. 2. Use following equation to calculate volume of sample at time of measurement. Volume = 157.97 − 7.
DMM600 Duff Moisture Meter sieve is included with the DMM600 for this purpose. Forcing the sample material through the sieve will improve measurement accuracy and repeatability. The heterogeneity of material size can be characterized by making repeated measurements of the same material. Place the duff in the sample chamber and make a measurement. Remove the duff from the chamber, restore its natural structure by working it by hand then put the duff back in the sample chamber and make another measurement.
DMM600 Duff Moisture Meter The accuracy is approximately ± 4.0% at 60% volumetric water content and approximately ± 1.5% at 30% volumetric water content. Measurements on materials that are highly heterogeneous in fragment size will provide less accurate results. DMM600 calibration 70 volumetric water content (%) 60 50 40 30 20 10 0 28 30 32 34 36 frequency (MHz) 38 40 42 FIGURE 3. DMM600 Standard Calibration 5. PCDMM Software 5.
DMM600 Duff Moisture Meter FIGURE 4. PCDMM User Interface Display 5.2 Calibration Equation The frequency output of the DMM600 is converted to water content using a calibration equation. The response of the DMM600 to changing water content is best described with a quadratic calibration equation. A factory calibration is part of the DMM600 operating system and will always be displayed. The factory calibration to convert frequency (MHz) to volumetric water content is: VolumetricWater Content = 5.288 + 5.
DMM600 Duff Moisture Meter 5.3.2 Indicators Three circles provide serial communications information. The left circle indicates which serial communications port is selected. The circle is green when the connection is successfully made. The TX circle is green during transmission from the computer to the DMM600. The RX circle is red during transmission from the DMM600 to the computer. 5.3.
DMM600 Duff Moisture Meter samples to obtain samples with a range of water contents, and the measurement process repeated on the wetted samples. 6.3.2 Detailed Calibration Procedure Spreadsheet file DMM600 calibration spreadsheet.xls is provided with the DMM600 to assist with calibration calculations. 1. Collect a sample of the material to be used in the calibration that is four to five times the volume of the sample chamber. Sample chamber volume is 3 approximately 140 cm .
DMM600 Duff Moisture Meter 11. Repeat steps 2 through 8. 12. Repeat steps 9 through 11 for other target volumetric water contents to provide a range of calibration water contents. 13. Derive the calibration equation using polynomial curve fitting such as the trendline function of Microsoft Excel. 7. Maintenance 7.1 Changing the 9-Volt Battery The 9-volt battery is installed behind the display. To replace the battery, remove the 3 outer screw from the display end cap and slide out of the main cylinder.
DMM600 Duff Moisture Meter 8.2 Microwave Oven Method For this method a microwave oven is required and sample containers suitable for use in microwave oven. Procedure 1. Weigh and record the weight of sample container 2. Place the sample in the container and record the weight of the container and sample. 3. Place the container with sample in the microwave oven with the heat sink and turn the oven on for 3 min. The heat sink can be a cup of water covered with a paper towel.
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