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Moisture Meter Guidelines
Supplemental Information for Display on HGCA Website

Campbell Anderson
CCFRA, Chipping Campden, Glos. GL55 6LD 

Contents

1. DICKEY-john Instruments *

2. Pfeuffer Instruments *

3. Protimeter Instruments *

4. Sinar Instruments *

5. Unitron Instruments *

6. Wile Instruments *

7. Other Instruments *

1. DICKEY-john Instruments

Multigrain
Instrument Details. This is a whole grain instrument the shape of which is similar to an upright electric kettle. The measuring cell is located on the top with an LCD and the operating buttons on a sloping surface above the handle. The commodities are selected as numbers 1 to 12 and a table relating number to commodity is displayed on the back upright surface opposite the handle. There is also a selection (known as chart mode) to obtain an instrument reading which can be looked up on a chart to relate this number to the moisture content of additional commodities. The instrument is also supplied with a sample cup, a 198g check weight and instructions.

Optional extras are accessory weights of 50g (when measuring linseed) and 100g (when measuring sunflower and oats).

The instrument uses automatic temperature compensation.

Operation. The scale should be checked with the test weight.

The sample cup should be filled with the crop to be tested. The commodity is poured at a slow steady rate into the measuring cell over the central cone. When the upper right of the display turns on the rate of pouring should be slowed. When a number flashes on the display pouring of the material is stopped and the final reading is shown when the display becomes steady. The cell is then emptied.

Comments on Use. The test instrument was deceptively easy to use. It was possible to get a reading from the instrument when the material was not loaded according to the above procedure: i.e. filling rapidly. This reading is generally incorrect, but could be sufficiently repeatable to mislead the operator.

Feedback from the manufacturers stated that it was not mandatory to halt loading the instrument once a number starts flashing on the display. They also stated that if the sample is loaded too fast the display would remain flashing until the instrument switches off: this did not occur with the test instrument.

When loading the instrument there is considerable grain spillage over the surrounding surface.

GAC 2100

Instrument Details. This is a tabletop instrument that principally uses capacitance to determine commodity moisture. It also measures grain density (hectolitre weight) and sample temperature.

Self-checks are performed on initial switching on and before each measurement. The instrument uses automatic temperature compensation.

There is a hopper on the top of the unit into which the commodity is poured. The front sloping panel has an LCD and a control panel with touch switches. At the front bottom left is a removable sample drawer: optionally, this can be removed and the instrument can be sited above a hole in the bench leading to a larger waste repository.

Up to 64 different commodity calibrations can be stored and recalled. These calibrations can be adjusted if required. Only authorised users can alter calibrations numbered 1 - 40 and this requires breaking of a seal on the rear of the instrument. Calibrations numbered 41 - 64 are considered unofficial calibrations and can be readily accessed. There is an audit memory which records data changes made to the instrument affecting moisture measurement and display.

The sample can be identified by either a sequentially increasing number (which can be reset after password entry) or a user entry before sample measurement that may contain alphanumeric characters selected from a character screen.

Results can be printed out by connecting to an optional printer. The instrument can also be connected to a computer either directly when adjacent or remotely via modem connection. The computer is usually used by authorised personnel to monitor and change calibrations within the instrument.

Operation. The commodity for testing is selected with keyboard entries. A sample is poured into the hopper located on top of the instrument (and an optional sample ID is entered). The sample load button is depressed and the cell is automatically filled and levelled. The test result of moisture, hectolitre weight and sample temperature is displayed together with commodity selected. Depressing the unload button drops the grain into the holding sample drawer (or a larger bin under the bench).

Comments on Use. The instrument is straightforward to use.

The choice of commodity from the possible 64 is made from 8 pages of 8 commodities: it would be useful to have some short-cut method of selecting the most frequently used materials. (See comments on the newer model).

A button needs to be pressed at the end of measurement to empty the cell: this seems unnecessary and it would be an improvement if this were automatic.

The section on daily maintenance of cleaning the instrument is buried on page 65 of the instruction manual: it would be an improvement if this was referred to in the introduction along with the other summary information contained in that section. This has been noted by the manufacturer.

There are on screen instructions detailing the steps that the user should make apart from at the end when there is no instruction to press unload at the end of the cycle.

New Model GAC 2100NB and GAC 2100a (not tested in this study)

Instrument Details. The instrument supplied for test was an older style GAC 2100 in dark brown and cream livery. The styling has since been updated to a black body with a blue front panel. The calibrations used in the UK are the same as in the older model. There are new communication options which the literature claims simplifies data logging and allows control of the operation of an adjacent instrument with a personal computer.

There is a quick key mode available to allow selection from 3 different most used commodities.

Additionally the GAC 2100a has been introduced which has a grain sensor in the hopper that allows integration with a grain sampler for continuous (30s cycle) automatic measurement. Grain is automatically dropped into the cell and the sample is automatically unloaded after the results are printed or transferred to a computer.

GAC 2100 AGRI (not tested in this study)

Instrument Details. This instrument has been recently introduced and is a less expensive modification of the 2100 with reduced facilities but still meeting the needs of the large-acreage farmer.

It principally uses capacitance to measure sample moisture. It also measures temperature and hectolitre weight. There is automatic temperature compensation of the moisture value.

Eight re-programmable calibrations can be held in the instrument.

The sample measuring cycle is increased compared to the 16s cycle time for the GAC 2100.

2. Pfeuffer Instruments
These instruments do not have calibrations with UK commodities.

HE 50

Instrument Details. The instrument combination comprises a rectangular measuring box with LED display and rotary selector switch for commodity. There is a separate grinder/cell that locates onto the instrument by three connecting pins (with three additional larger pins to aid correct siting). The unit is powered by a 9V battery. Supplied is a NiCad rechargeable battery and charger, carrying case, sample cup, cleaning brushes, reamer for cleaning the cell thread and instructions.

There is also additional equipment for bias adjustment for each individual calibration. This was not provided with the instrument used for testing. This unit plugs into the main instrument, bias adjustment is made and then it is removed. This allows use by authorised personnel only if required.

The upper and lower surfaces of the grinder have a multi-pointed pyramid structure. The bottom chamber has a handle for holding in one hand. A ratchet locates into the top unit of the cell. The grinding design is similar to the Unimeter Super MkII, with the advantage of the ratchet to aid grinding.

The instrument uses automatic temperature compensation.

Operation. Ten ml of commodity, measured in the sample cup, is poured evenly into the bottom part of the cell. The top unit of the cell is screwed onto the bottom part with the aid of the ratchet. This grinds the material until a stop is reached which sets the ground sample depth.

The appropriate commodity is selected with the rotary switch, the measuring button is pressed and the reading is displayed on the LED after confirmation of the commodity.

The cell is removed from the instrument, opened and cleaned.

Comments on Use. The instrument is straightforward to use. Use of the ratchet when grinding the sample reduces the effort required to an acceptable level compared to the Unimeter Super MkII which use the same grinding design.

Cleaning the top surface of the cell is readily performed with the (nail) brush provided. Cleaning the bottom surface is more difficult as it is recessed in the bottom of the cell. For wet samples after removing the bulk, the instructions recommend grinding with a dry sample before finally cleaning the cell. This is more time consuming. If it were practical to design unscrewing the side of the cell to access the bottom, this would be a welcome improvement: however this might introduce problems of seating and consistent sample presentation. Operation is noticeably longer than using whole grain instruments.

HE 60 and HE 90 (not tested in this study)

Instrument Details. These additional instruments from the Pfeuffer range are each built into a wooden carrying case. The HE90 is supplied with a ticket printer with options of a real time clock and an RS232C interface.

Operation. Using the supplied grinder, the sample is ground into the measuring cell followed by separate compression. The product is selected from a keypad and the moisture reading is read off the LCD.

Granomat

Instrument Details. This is a tabletop instrument that principally uses capacitance for moisture determination. Hectolitre weight and sample temperature are also measured. Automatic temperature correction to the measured value is made. Self-checks are carried out when the instrument is switched on.

The instrument is supplied with a 600 ml plastic jug and an instruction booklet.

On the top left of the unit is the sample hopper with the sample receiving tray underneath at the bottom. The right half of the instrument has a sloping front panel on which is the backlit LCD and control panel. An integral printer is sited on the top right. There is an RS 232 port and a centronics parallel interface on the rear panel for printer connection. Menu choices allow automatic printing to the appropriate printer.

Seventeen calibrations are programmed into the instrument with the facility for storage of up to 200 commodities. Each calibration can be individually adjusted (bias): this facility is password protected.

An incremental number is assigned to each sample (displayed on the printout after measurement and not on the LCD) and the user can program the starting number. There is also the facility to input up to 6 lines of 16 characters for printing as a header.

Entering of calibrations requires specialised software and connection to a computer. In calibration mode standard samples can be measured to obtain calibration data. Before an instrument measurement is taken the reference value for the sample is input. This calibration data can be transferred to a computer or output to a printer.

The instrument is officially approved for class II in Germany.

Operation. The commodity to be measured is selected from an alphabetical list of calibrations. Sample, 600 ml, is poured into the hopper and the measure key on the keypad is pressed. The sample is loaded into the cell automatically, measurements are performed and the sample is emptied into the receiving tray. This must be emptied before a subsequent sample can be measured. This cycle can be continued while the commodity remains unchanged.

Comments on Use. Sample presentation and measurement (once familiar with the instrument's sometimes unclear messages) is straightforward and relatively rapid.

On occasions, the instructions displayed on the LED indicating the next operation to be carried out, although not incorrect, appear misleading. For example, after a measurement the instruction is 'press any key' which suggests that the same operation will be carried out independent of which key is selected. However, pressing 'measure', which is a short cut action for the same commodity (provided the next sample is loaded into the hopper) will immediately start a measuring cycle, whereas any other key will take the user back to the commodity selection screen.

When the instrument is switched on there is an initial series of beeps showing that the electronics are working correctly. This is followed by a period when the display is blank while self-checks are being carried out. This is disconcerting to the user as there is no reassuring message to show that the instrument has not developed a fault.

After the self-checks and before the instrument will function correctly it is necessary to remove and replace the sample receiving drawer. There is no mention of this in the instruction booklet. This has been noted by the manufacturer.

The selection of the 6 lines with 16 characters of text is achieved by moving round an alphanumeric display on the LED using arrow keys. This is time consuming and will probably only be used as a header for the testing laboratory and not for information on the sample. The manufacturers consider that the data would normally be entered using a connected computer: use of the keypad would be secondary.

3. Protimeter Instruments

Grinder

Instrument Details. All Protimeter instruments are supplied with the same model of grinder/compressor that locates by three lugs onto an electrode assembly of similar design on the body of each instrument. The sample cup is an aluminium tube that locates around the electrode.

The grinder/compressor has a small hopper at the side for loading the commodity and has a slider on the rotating arm for selecting grinding or compression. Comminution is a slicing action as on a kitchen grater. Compression is by a piston with a clutch that slips (and clicks) when a consistent pressure is achieved.

Operation. At the start of sample preparation, the grinder/compressor piston should be at the top of its travel. Grinder operation is selected by moving the slider on the arm away from the grinder/compressor. The aluminium tube is placed on the electrode and the grinder/compressor is located around the cell on the three lugs on the base of the instrument electrode. Commodity (10 ml) is poured into the grinder/compressor using the supplied scoop and the sample is ground. When the sample is fully ground, the slider is moved inwards to select compression and the handle is rotated clockwise until the clutch clicks at the pre-set pressure. The sample is now ready to be measured (see the individual instruments for the procedure). After measurement, the piston is raised until the clutch clicks, then grinding is reselected. The unit is removed and cleaned.

Comments on Use. It takes a short while to become familiar with the grinder operation. Then the equipment is easy to operate. The grinder dismantles conveniently with offset lugs in appropriate positions to prevent combining parts in the wrong orientation.

It takes around 45 s to clean the grinder between grain samples of trading moisture. Wetter samples and oilseed rape take a little longer: for very wet grain, the manufacturer recommends that the grinder should be initially cleaned by putting through a dry sample.

Digital Grainmaster

Instrument Details. The Grainmaster ensemble consists of a squat rectangular measuring instrument with electrode and removable grain cup (aluminium tube): there is a single LED display that shows the sample moisture content. The combined grinder/compressor is standard. The instrument is supplied with two commodity keys, for measuring wheat/rye and for barley/oats: other keys are available. It also includes a sample scoop for dispensing 10ml of commodity, cleaning brush and a cloth carrying pouch/case. There is also an instruction booklet, a calibration chart and two check test caps.

The commodity keys have an adjustable screw on the top surface. This is marked with a position for setting where the calibration matches the reference method. The screw can be turned to adjust for an offset if required.

The instrument has automatic temperature correction (ATC) that is selectable by a recessed switch on the bottom surface.

Operation. The instrument should be checked by measuring the readings from the two check test caps when ATC is switched off and the wheat key is inserted.

The program key for the commodity under test should be inserted into the instrument. ATC should normally be selected.

With the grinder/compressor attached, a 10ml sample is ground and compressed. The measuring button on the top of the instrument is pressed and a reading is taken. The grinder/compressor is removed and cleaned as required.

With ATC switched on the reading will have been corrected for temperature. With ATC off, a manual correction for temperature of -1/100th of the reading for every 1°C above 20°C and +1/100th for every 1°C below 20°C should be made.

Comments on Use. Once familiar with the operation of the grinder/compressor the instrument is straightforward to use.

Taking readings with the check caps requires use of the wheat/rye key with ATC off. Care should be taken to switch the ATC back on and to change the key if required.

It is not easy to precisely align the screw adjustment on the commodity key with the reference mark. If a bias adjustment has been made there are no dial marks to record the position for future reference.

When grinding, the usual action is to grip the instrument to counteract the grinding rotation. Care should be taken not to disturb the key with the heel of the hand.

The instrument does not always give a clear indication when the sample moisture is too high (usually a figure 1 at the left of the display). Noticeable with high moisture oilseed rape it may give a low moisture reading that does not settle to a final figure. This can initially be confusing to the operator.

Grainmaster 900 and 900e

Instrument details. These two instruments consist of a squat moulded reverse L-shaped measuring instrument with electrode and removable grain cup (aluminium tube). There is a dual LED. The top display shows sample moisture or temperature probe reading (if connected) or calibration adjustment (if selected): the bottom display shows the selected crop or function or the sample cell temperature when making a measurement. The combined grinder/compressor is standard. Also supplied are a moulded plastic carrying case, sample scoop for dispensing 10ml of commodity, cleaning brush, test cap, instructions and a calibration chart.

Calibrations for 10 crops are programmed in as standard. Additional crop calibration may be installed using a PC and purpose designed software. The user, dealer or service centre can carry this out.

The 900e (shown above) differs from the 900 in the following respects.

It has the facility for averaging of readings

It can print results on an optionally available ticket printer

There are four additional keys for quick selection of frequently tested commodities.

Both instruments have keys for selecting the crop or function.

The instruments are calibrated to the relevant International and British Standards. If required the calibration for each commodity can be adjusted for bias individually up to a maximum offset ± 1.5% moisture.

Operation. The instrument has a self-test function that is carried out in conjunction with the test cap.

Automatic temperature compensation (ATC) is selectable by scrolling up through the function menu. If not selected the instrument is only calibrated for samples at 20°C. If the temperature varies from 20°C then manual correction is required.

The commodity to be tested should be selected by scrolling through the menu (or by using the short cut keys on the 900e). The instrument powers up with the previously selected commodity.

With grinder/compressor attached, a 10ml sample is ground and compressed. The on-button is pressed and the commodity indicated should be checked as correct. The moisture reading should be taken once the moisture and cell temperature readings have settled to constant values. This will only create a time problem if there is a large difference between the sample and instrument temperature: (a situation that is not recommended).

The grinder/compressor is removed and it plus the cell are cleaned as necessary.

Comments on Use. Once familiar with the grinder operation the equipment is straightforward to operate.

Operation with ATC on is a critical function. It is possible to turn ATC off. If turned off, the temperature displayed on the lower LCD flashes only while the ON button is depressed: this flashing display is not mentioned in the instruction manual. With ATC either on or off the final temperature display is static. It would be additionally reassuring if an indication (e.g. a dot in a corner of the display) was shown to confirm ATC selection.

GrainMini V (not tested in this study)

Instrument Details. This is a cylindrical instrument, 130mm high by 80mm diameter. The grinder/compressor fits onto the bottom of the instrument (as designated by the manufacturer): when grinding, the instrument is then conventionally upside down. There is an ATC switch on the side. The instrument is supplied with two crop reader rings for wheat/rye, and barley/oats with other rings optionally available. Also included are the aluminium grain cup, a 10ml scoop, quick check test cap, cleaning brush, calibration chart, instruction booklet and carrying pouch.

Operation. The operation of the instrument should be checked using the Quickcheck test cap with ATC switched off and the ground wheat reader ring in place.

For a sample reading, the required crop reader ring is placed on the top of the instrument to cover the 0-100 scale. The arrow on the ring should be aligned with the arrow on the instrument for calibration to the relevant standard. Rotating the ring will make any offset (bias) adjustment that is required.

After grinding and compressing a 10 ml sample, the red button on the side of the instrument is pressed and the knob on the top is turned until a second light is illuminated. The pointer is now aligned with the sample moisture content, which can be read off the scale.

The grinder is removed from the instrument and cleaned as required.

GrainProbe (not tested in this study)

Instrument Details. The instrument is 1680mm in length with a probe working length of 1400mm. At the top of the probe, incorporated in the handle, is a large LCD that indicates sample temperature and moisture. It is calibrated for wheat, barley, oilseed rape, peas, beans and linseed.

4. Sinar Instruments

AP6060 - 001

Instrument Details. This is a conventionally shaped capacitance meter, basically rectangular in shape rounded at one end where the raised removable measuring cell is located. On the top surface are an LCD, a series of 7 commodity selection buttons and 11 buttons for various operations.

The instrument incorporates an oscillating weight balance that corrects for the sample weight and has automatic temperature compensation.

Also supplied is a sample loading hopper and a set of instructions. There is an optional hectolitre weight measuring kit.

A maximum of 254 samples can be averaged.

Readings can be output to a printer through the integral RS232 port. This port can also be used to transfer calibrations from one AP6060 to another.

The calibrations for each commodity can be adjusted individually for offset (bias).

Operation. A daily check of the mechanical and electrical integrity of the hardware of the instrument with an empty cell can be carried out using the Cal/Auto button. This does not confirm correctness of software calibrations, bias adjustment or instrument tolerances.

The sample is loaded into the cell using the clear Perspex hopper. After loading, a sprung loaded slider is released allowing the material to fall into the measuring cell. The hopper is then removed before measurement. The instrument is switched on, the commodity selected (with the corresponding number confirmed on the display) and the %H20 button is pressed. The moisture value is displayed. The cell is removed from the instrument and emptied.

Comments on Use. The instrument is easy to use. Sample throughput can be relatively rapid. It is relatively heavy for a portable instrument.

It would be useful if there were an indication on the display when a bias correction has been applied to the calibration. This could be a symbol in one of the corners or a preliminary display of the correction.

Note. This is the basic instrument. The seven calibrations supplied with the instrument can be selected from a wide range of commodities.

For grain samples above 18% moisture and oilseed rape above 13% moisture an alternative model is available: this is for up to 35% moisture for cereals and up to 25% moisture for oil seeds. The unit operates in the same fashion as the AP 6060 - 001; however the sample cell has different electrical characteristics.

Sinar Chopin TM

Instrument Details. This is a tabletop instrument that principally uses capacitance for moisture determination. It also measures sample temperature and grain density (hectolitre weight).

It is supplied with a 1 litre jug, an instruction manual and a manual for use in calibration.

On switching on, self-checks are made. The instrument uses automatic temperature compensation.

On the top of the unit is a loading hopper that requires 1 litre of commodity: this has an integral sensor to detect that sufficient sample has been loaded. The front sloping panel has a back-lit LCD on the left and a control panel on the right including a numeric and compressed alphanumeric keypad (3 letters per key selected by one of 3 shift keys). At the bottom of the front panel is the sample receiving drawer.

The instrument can store up to 128 calibrations and is pre-programmed with 13. The most frequently used calibrations can be selected on a short-list. These calibrations are password protected from unauthorised alteration. An audit trail for alterations to the set-up of the instrument is available. It comes equipped with an internal modem for remote diagnostic evaluation and remote calibration update.

The existing calibrations can be modified or new calibrations entered after passing through password protection screens. Measurement of samples on the 'linear' scale of known reference moisture values should be taken. These pairs of data points are entered into the instrument and a linear, quadratic or cubic curve can be fitted to the data: this is displayed graphically, together with coefficients, on the LCD. There is the option to update the calibration by modem, a service that is provided by Sinar Technology.

Each sample can have an optionally recorded ID. Each numeric key is used to input one of three colour coded text characters. The input character is selected by the correspondingly coloured shift key.

A printer can be used to print out the sample results.

Operation. The required commodity is selected from the whole list or scrolling (in either direction) through the user defined short-list. This remains the selection until changed. One litre of grain is poured into the hopper and it must cover the loading sensor. If a one line comment is required the '*' key should be pressed and the details entered before starting the measuring cycle. After the test key is pressed, the instrument will automatically load the sample into the cell, make the measurements and discharge the material into the receiving tray. The results are shown on the LCD. If a printer is connected and selected the details will be printed.

Comments on Use. The instrument is very easy to use. The display is friendly in that it informs the user about which stage of the cycle the instrument is at or what is the next required action by the user.

The use of the (alpha)numeric keys together with a shift key to input characters is a reasonable compromise for inputting data for a short ID in the absence of a keyboard.

Grainspear (not tested in this study)

Instrument details. The instrument is designed to measure moisture and temperature in bulk samples that have been in place for at least 2 weeks (to allow settling to a resting bulk density). At the measuring end are two sets of fins at right-angles, the 'war-head' made of metal (the appearance is like the flights of an arrow). The shaft length can be either 1 or 2 metres long. Towards the top is the read-out unit (averager) from which displayed moisture and temperature readings are taken. Above this the shaft is covered to assist grip when spearing into a heap.

The instrument is programmed with six standard calibrations with other optional calibrations available. These can be individually offset (biased) if required.

When the read-out unit is in averaging mode it can show i) the average moisture of the samples taken, ii) the total number of samples being averaged or iii) the current sample moisture value.

Temperature compensation is automatic.

5. Unitron Instruments

Unimeter

Instrument Details. This is a 'conventionally' shaped capacitance meter, rectangular in shape with a raised portion at one end for the measuring cell. There is a convenient carrying handle built into the instrument. The display is an analogue meter with direct reading on separate scales for barley, wheat oats and rye. For the other 10 commodities, a reading on a scale from 0 -100 is taken. A series of conversion scales are present on the meter relating these values to the individual commodity moisture values.

The instrument is also supplied with a temperature probe and instructions.

There is a slotted adjustment screw on the base. The adjustment affects the meter deflection, hence all the scales simultaneously. Therefore, if individual biases are required the user must remember the position and reset the screw for the particular commodity under test.

Operation. There is a test position for the battery, which should be checked before operation. The sample cell is filled with commodity until the white top to the centre of the cell is covered. The test button is pressed and the moisture value is either read directly or a number from 1 - 100 is taken for cross-referencing on the relevant conversion scale on the top or bottom of the instrument.

Comments on Use. It was straightforward to fill the cell and test the sample. However the figure in the value after the decimal point has to be read by interpolation, as the scale is not marked in divisions of a percent. It is awkward having to turn the instrument upside down for some of the conversions. The scales are not linear; becoming more compressed as the moisture level rises.

There was some sample spillage onto the surrounding work surface

Unimeter Super Mk II (not tested in this study)

Instrument Details. The instrument is rectangular in shape with rounded front and back sides to make holding easier. On the top left is an analogue meter for taking the measurement. The measuring cell is built into the top right of the instrument. The cell is very similar to that used on the Pfeuffer HE50 with a multi-pointed pyramid structure to the top and bottom surfaces. The turning handle is built into the cell top surface. In the arms of the handle are a 9ml (for grain) and an 11ml (for small seeds) sample recess for measuring the commodity quantity. Also on the top of the instrument are two buttons: one is for testing the battery and the other is used when making a measurement.

Operation. The required sample volume is put into the cell and it is shaken to distribute it evenly. The top of the cell is screwed into the bottom until the stop is reached. The measuring button is pressed and the meter reading is recorded on the appropriate scale.

Comments on Use. Grinding of the sample requires considerable manual effort and is therefore an uncomfortable operation.

When the stop is reached the measuring button is located under one of the arms of the grinding handle thus restricting access to it.

There is what appears to be an adjustment screw on the top of the instrument but no mention of its operation is made in the instructions.

6. Wile Instruments

Wile-55

Instrument Details. The instrument is shaped as a cylinder, with the measuring cell at one end on the top together with a screw cap that has a central piston: integral is a raised rectangular housing on which is an LCD digital display and 2 buttons. It automatically compensates for temperature variation.

The instrument can measure the moisture of 16 commodities that are selected by corresponding number from a list that is located on the side of the raised display housing. There is also an additional position that gives an arbitrary (sic) number that can be used in conjunction with separate auxiliary scales.

Each calibration can be individually adjusted (biased) if required. Sample readings can be averaged.

It is supplied with instruction leaflet and a flexible plastic case.

Operation. The cell is quarter filled with commodity. The instrument is shaken to settle the material around the measuring sensor then filled to the brim. The cap is screwed onto the meter until the piston in the cap is level with the rest of the cap. The power button is pressed and the previously selected commodity number is displayed: this should be changed if required. If any changes to the calibration have been made, the size of the correction is displayed next. The moisture content then appears on the display.

Comments on Use. The instrument is straightforward to use.

It is tempting to blow into the measuring cell to clean out the dust but, as the instructions point out, this should not be done as it could introduce water into the cell.

The commodity currently selected is only displayed as part of the measuring sequence: there is not a commodity selection procedure independent of the measuring cycle. If another choice is required changes must be instigated in the short time interval when the commodity number is displayed.

When changing between commodities, particularly if frequently, it is slightly annoying that the user cannot scroll in both directions through the commodity list (e.g. changing from barley to wheat requires 16 presses of the button).

Wile-35 (not tested in this study)

Instrument details. The instrument is shaped as a cylinder, with the narrower measuring cell on the top together with a screw cap that has a central piston: integral, on the side is a raised rectangular housing on which is an analogue meter display. Recessed in the bottom is the on/off/rotary switch. It is supplied with a conversion slide-rule and flexible plastic case.

The analogue meter has direct reading scales for wheat, barley and oats and a linear scale from 0 -50. Readings for other commodities are taken using this scale and, with the aid of the supplied slide-rule, converted to the moisture content.

Readings are not temperature compensated. The reverse of the slide-rule gives the correction that must be made for the difference between the sample and instrument temperatures. These two temperatures must be measured separately.

Operation. The instrument is switched on and the meter adjusted to 50 on the linear scale with the on/off/rotary switch. The cell is quarter filled with commodity and the instrument is shaken to settle the material around the measuring sensor. The cell is then filled to the brim. The cap is screwed onto the meter until the piston is level with the top. The reading is taken on the appropriate scale.

7. Other Instruments

Agricomputer

Instrument Details. This is a 'conventionally' shaped capacitance meter, rectangular in shape with a raised portion at one end for the measuring cell. There is a convenient carrying handle built into the instrument. There is a single line LCD on a sloping surface down from the cell and a control panel on the lower top surface near the handle.

The instrument can also give a value for hectolitre weight and a 100ml cup is supplied. Also supplied are a temperature probe and a moulded plastic case.

There is a connection port on the side for attaching optional accessories. Accessories available are a hay/straw probe for measuring the moisture content of hay or straw bales, an RH-Tester for measuring relative humidity and a PH-Tester for measuring the pH value of soils.

Temperature compensation is automatic.

The instrument is programmed to test fifteen commodities. Up to 99 individual readings can be averaged.

Individual offsets to each scale can be made. The instrument is powered by two batteries that should be replaced sequentially. Removing both batteries together will reset the instrument to the standard calibrations.

Operation. After switching on, the commodity is selected by scrolling through a list. To measure a sample the test pad is pressed and the display shows 00 and a vertical arrow. The cell should be filled from a cup. The number on the display rises and filling should continue until the display shows 99, 100 or 101 and a horizontal arrow. If overfilled the cell must be emptied and the cancel button pressed. In these circumstances removing a small quantity of grain does not allow measurement. With the display between 99 - 101 pressing the test pad again displays the moisture value. The value can be transferred to a memory for later averaging.

If it is suspected that the crop temperature is very different from that of the cell, the cell temperature with the crop in place can be displayed by pressing the left-hand arrow on the pad. This value should be stable before recording the crop moisture value.

If there has been an offset made to the scale, an asterisk will appear adjacent to the displayed moisture value to show that it is not a measurement to a standard calibration.

Comments on Use. The instrument was very easy to use. There was some spillage to the surrounding surface when filling the cell. Care has to be taken not to overfill the cell.

The instrument has calibrations for soft wheat and hard wheat. All measurements on UK grown wheat (T. aestivum) should use the soft calibration. This requires clarification in the instructions.

There are separate calibrations for spring and winter barley. This is all very well if the barley type is known, but what happens when it is not? In this study all barley samples were tested on the winter barley calibration.

Harvester J130

Instrument Details. The instrument is a small rectangular box with a sweep to a wider portion on the front right. It has an LCD, three operation buttons and an integral measuring cell with screw for crushing a single layer of grain of sample size around 1ml. Also supplied are a moulded plastic case, two sample trays, tweezers, cleaning brush and instructions. The sample is loaded onto a small tray that is inserted into the side of the instrument

Operation. After switching on the instrument, one of the six commodities is selected. The sample tray is inserted and the grain is crushed using the screwed crusher. The moisture value is displayed. The apparatus has an averaging facility for up to nine readings that is invoked with the 'ave.' button. Provided the power remains on, the number of readings since the 'ave.' button was pressed is shown. Pressing this button displays the average of these readings. The counter resets to one with the next reading: it is also reset on auto power off.

Comments on Use. The instrument is very easy to use and cleaning is rapid. The sample size is small (around 12 wheat kernels) so any large variation in moisture content of individual grains would have a marked effect on the measured value. As its name suggests its main use is for testing the crop in the field for suitability for harvest. It is not recommended for trading, as the sample size is very small.