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In general the paper pad material for the AP4 calibration plate is not critical, as long as it is completely clean and grease free.
Filter or blotting paper is good. It is absorbent and will not contaminate the water used. Make sure it is a paper-based filter, not plastic. The finer the fibres in the paper the more water it will hold and the longer it will last before becoming dry.
We currently use blotting pads 32x60mm in size cut from sheets supplied by a company called Moreton Hall Press. P/N: DEL26084
Problem If a USB to RS232 converter is being used and the COM port allocation is higher than 9, some software cannot cope and a communication errors occur. It applies to:AP4 retrieveHH2Read (old versions)Ls2win (old versions)SolutionThe software doesn’t like COM port allocations with double figures (higher than 9). To remedy this, please enter the COM port manually but type ‘\\.\’ before the com port. E.g. \\.\COM10Note: For HH2s and DL2’s the latest version of HH2Read and LS2win should resolve this issue and they can be downloaded from our website, if necessary (www.delta-t.co.uk).
We are frequently asked about making measurements of transpiration with the AP4.It is possible to convert from conductance readings to transpiration readings, and the basic equation used to define conductance will do this (see the AP4 manual, page 85):
E = cv (wvdc - wvdl)
where E = flux density of water vapour, in g m-2 s-1, cv = conductance in velocity units, m s-1, wvdc = water vapour density, at the cup RH and temperature, g m-3. wvdl = water vapour density, at the leaf RH and temperature, g m-3.
However, this measurement will only apply to the conditions within the cup itself. It cannot be used as a basis for calculating the transpiration loss from a plant or canopy because the leaf temperature, air temperature, vapour pressure deficit and boundary layer conductance will all be different in the cup from in the field. We don't include the option to measure transpiration rate in the AP4 so that users are not tempted to make this extrapolation.
In fact, although the ability to take a reading in transpiration units is built into the LI-COR LI1600, they also strongly recommend that it is not used as a basis for calculating in situ transpiration loss, and instead make the calculation based on the diffusion conductance. The paper published by Dale McDermitt at LI-COR (McDermitt, D.K., 1990.Sources of Error in the Estimation of Stomatal Conductance and Transpiration from Porometer Data.HortScience 25: 1538-1548) contains a very good explanation of how to do this.
Please refer to page 117 in the user manual as well as using these steps to try and resolve any odd operating problems on the AP4:
Remove the roll pin at the hinge of the head to separate the two halves. Measure the resistance of the thermistor bead in the leaf half at the point where it is soldered to the printed circuit board. It should be about 100Kohms. It is not easy to measure the resistance of the cup half thermistor directly, but you can measure the resistance between the blue wire (analogue ground) and the yellow wire (cup temperature). This should be about 46 - 48Kohms. It should be obvious if these connections are broken or have lifted from the PCB. Re-soldering them should solve the problem. Notes:
Are there any restrictions on upgrading old DL2's to current EPROM and LS2e versions ?
The current EPROM version is fully compatible with all DL2 and DL2e models.EPROM version 3.0 or later is required for LS2 and LS2e compatibility.
This applies only to the DL2e logger. It is mentioned in the DL2e Hardware Manual p18. The DL2e has never had the year capability in its time-stamp, only day+month. In leap years when there is a February 29 date some action may be needed if the logging period extends beyond February 28 into March. The following notes explain what to do.
There are two possible problems:
1. The DL2e datafile may not contain the February 29 date.2. The DL2e logger will report the date wrongly (by one day) until it is corrected.
The solutions are:
1. Always use the Delta-T Dataset Import Wizard in Excel to import data from DL2e datafiles that cross a February 29 leap year date.In the Dataset Import Wizard the user is asked to supply the year that the data in the .DAT (or .BIN) file applies to. It then provides this information to Excel so the resulting Excel file has all dates either side of February 29th automatically corrected where necessary. Note that this will NOT happen if the .DAT file is imported into Excel simply as a .CSV file. The user will then manually have to correct the dates after February 28.
2. If you want the DL2e to report the correct date, then at some convenient time on or after March 1st, download the data from the DL2e as above
Logger Relay Limits: The number of items powered though a logger relay (DL2e or DL3000) is limited by the DC and surge currents. The logger relays can each switch 2A DC or about 5A for a brief surge of a few ms. ITEMS LIMITED; Max number of items per Relay; Notes
M20 Modem; 1; Limit from 2A transmit peakML1 ThetaProbe; 11; Inrush surge limitedEQ1 Equitensiometer; 11; Inrush surge limitedML2 ThetaProbe; 16; Inrush surge limitedML2x ThetaProbe; 16; Inrush surge limitedSM200; 16; Inrush surge limitedEQ2 Equitensiometer; 16; Inrush surge limitedPR1/6 Profile Probe; 8; From DC limit (PR2 is the same)PR1/4 Profile Probe; 12; From DC limit (PR2 is the same)TVB1 Voltage Regul'r; 1; Inrush surge limitedTVB1 Voltage Regul'r; 2; From TVB1 s/no 930VP1 Psychrometer; 1; Motor stall limit
ITEM LIMITS not normally a problem: ACS1; AC excit'n Source; 21 AN3; Anemometer; 18 BS4; Barometer; 125 ML2x; Thetaprobe; 50; ??After s/no.102-25 May 2001EQ2; Equitensiometer; 50; ??Based on above ML2x RHA1; RH; Sensor; 500 RHT2; RH Sensor; 50 SWS; Surface Wetness Sensor; 200 TO CALCULATE LIMITS for mixtures of items on one relay: The sum of (number of items/per Relay) for all items must be <1. eg: 8xML1 and 2xPR1/6 on one relay is just ok, because (8/11) + (2/8) = 0.98 SLAVE RELAY If you must switch higher currents use an external relay, with high current contacts. Power this slave relay's coil from the Logger relay. ??For example, on "12V"-powered Loggers a relay with 10A DC, ??nnA surge contacts would enable 5x the number of logger-relay powered items, shown above.
There is a bug in the "Defer first TIMED data until" option when starting logging. The warmup relays for any powered sensors are left ON until the first LOG. Thereafter, the logger and warmup relays behave normally.
This can be serious if the powered sensors take a lot of current, and if the deferred period is long (hours or days). The logger and sensors power supplies may be substantially drained during this initial period.
The only workarounds are to avoid using the deferred start, or to minimise the length of the deferred period, and to allow for the current drain during that period.
Applies to: GP1, batch 10/xxx onwards
The battery holder was changed in 2010 and, as a result, changing the battery requires a different technique:
Pull the retaining lever away from the battery Lift the battery up so it is free from the retaining lever whilst also still pulling the retaining lever away from the battery: Pull the battery away from the connector sockets: Do the reverse of the above instructions to put a new battery in
Please also see video here:https://dl.dropboxusercontent.com/u/63165584/Removing%20battery%20from%20GP1.mp4
The following video explains the best way that this can be done:
Example in video is 8-way BF5 cable and GP1.
Site factors: In general, site factors assume you are measuring radiation on a horizontal surface ( ie radiation measured using properly levelled cosine-corrected sensors) so you should make no adjustment for this.
However, there may be circumstances when you want to look at radiation load on the canopy floor, when it is appropriate to take account of the slope. You can do this by changing the Intercepting Surface settings. The values you have to enter are the Azimuth and Zenith angles of the perpendicular to your surface.
The Azimuth angle is the angle from North (via East) of the steepest downwards slope.
The Zenith angle is the same as the maximum angle between your slope surface and horizontal.
Select a single sided surface (double sided is only appropriate to single leaves that receive radiation from both sides).Your values of radiation above and below will now be the same as if you measured them with a cosine corrected sensor in the plane of your surface.
You must use an external image editor to edit your image.
Paint the image with bright red (RGB 255,0,0) or another colour that does not normally occur in your image. You can check what colour HemiView sees this as, by loading the image and holding the cursor over a painted area - the colour is in the status bar. Make sure the 'ignored pixels' in Classifier Settings are selected and exactly match your displayed values.
Make sure you save your image as a .BMP, not as a .JPG image. JPG is a 'lossy' compression system and will only restore your careful work approximately.
When you classify the image in HemiView, make sure that the ignored areas show up as red, not black or white.
If you have records of Direct & Diffuse radiation:
The Solar Model requires values for the direct transmissivity, and for the diffuse proportion.Integrate your data to give monthly totals of Direct and Diffuse radiation.
Calculate the equivalent values using HemiView - Direct radiation integrals are given in the Total row at the bottom of the DirAb sheet, Diffuse radiation integrals are calculated by multiplying the DifAb value in the values sheet by the appropriate month value in the DifMonth sheet.
By trial and error, adjust the values of transmittivity and diffuse proportion to give best fit between your measured irradiance at the point, and the computed irradiance using HemiView. You may find that a single solar model setting will not give a good fit for the whole year, so it may be appropriate to find several sets of solar model settings that work at different times of the year, and only use the corresponding outputs for those times.
If you have records of Sunshine duration:
Calculate the percentage sunshine as the number of actual sunshine hours divided by the total possible sunshine hours (sunrise to sunset). Multiply this percentage by 0.9 to give an approximate value for the direct transmissivity.Set the diffuse proportion to a value of 0.1 for direct transmissivity >0.8 or < 0.2; to 0.2 for direct transmissivity between 0.2 - 0.4 or 0.6 - 0.8; to 0.3 for direct transmissivity between 0.4 - 0.6.
IMPORTANT NOTEIf you have distinct seasons with very different radiation characteristics, you will need to do these calculations for each season, so you have different solar model settings for different parts of the year. Only use your results for the period when the solar model is valid.
ISF: indirect site factor is time-invariant
DSF: you can calculate daily DSF values by summing DirAb and DirBe (or DirAbU and DirBeU) columns in the TimeSer sheet and dividing one by the other
GSF: is defined as (direct + diffuse below) / (direct + diffuse above). To calculate a daily value:
1. Calculate direct above and below as for daily DSF (above).2. To approximate diffuse above, start with the annual DifAb (or DifAbU) value in the Values sheet, apportion according to the monthly weighting in the DifMonth sheet, and divide by the number of days in the month.3. Calculate diffuse below by multiplying diffuse above by ISF.
For values spanning a series of days, repeat the above operations for each day and sum the radiation values before calculating the site factors.
For periods of a month or more:
DSF: you can calculate monthly DSF values by taking the appropriate values from the DirAb and DirBe sheets, and dividing one by the other.
GSF: is defined as (Direct + Diffuse below) / (Direct + Diffuse above).
1. Take Direct above and below from the DirAb and DirBe sheets.2. Calculate Diffuse above as DifAb annual value multiplied by the appropriate month fraction from the DifMonth sheet3. Calculate Diffuse below by multiplying Diffuse above by the ISF value
If we have no information about a particular lens, you will have to calibrate the lens yourself.
One way of building a calibration jig is to remove the spokes from a bicycle wheel and mount the camera at the centre. The holes in the wheel rim provide calibration points at regular zenith angle spacings, so you can measure their locations on a photograph and construct an equation which relates the position on the photograph to zenith angle.
In the meantime, you could scan, threshold and align the images, and analyse them using the Linear 180 lens. If you save the image properties as .hvs files, it will be straightforward to later re-analyse the images using the correct Camera Lens equation.
On initial power up the HH2 reports a sequence of messages such as "Readings Corrupt" OR, after taking a reading, the HH2 fails to display the "Store?" prompt and it is not possible to record readings.
To clear the error condition you need to cold-boot the HH2. Cold-booting will destroy any data that are already stored, so you might want to try to download any stored readings before proceeding (no guarantee of success if readings are corrupted).
To cold-boot the HH2 proceed as follows:
1. Disconnect the battery.2. Short out the battery connection terminals with a metal object, e.g. a screwdriver blade. 3. Reconnect the battery: snap the connector in place in a single continuous action.4. While doing so, observe the display and ensure that: a) the entire display blacks out b) no error messages are displayed c) the title screen 'Delta-T Devices Moisture Meter' is displayed.
For the record, the HH2 notifies you of the error condition only when it first detects the error, normally on power-up, e.g. "Readings Corrupt" messages that occur when it fails to cold-boot correctly. It then patches up the error where possible, for example, restoring the default linearization tables from ROM, and resumes quasi-normal operation. This means that it is able to take readings and doesn't report the error any more.
However, it is no longer able to store readings if:
a) the sequence of stored readings is damaged, it won't be able to retrieve readings beyond the damaged pointb) linearization tables are damaged, soft-loaded tables may have been lost, and readings may not be in accordance with the user's intended configuration c) other configuration settings are damaged it is no longer able to represent configuration settings in the data stream - because they are stored as differences.
Hence it withdraws the facility.
If the HH2 doesn't offer the possibility of storing readings, this is because it has detected an error condition (corruption of stored readings, linearization tables etc) which prevents it from storing any more readings.
Is the RS232 cable correctly fitted between the PC and HH2? Check that the cable connectors fit tightly. There may be problems with the 9-25 D adaptor at the HH2 end. You may have to try swapping with other cables or adaptors.
Are you using the right COM port? Check which serial port is used on the PC. Check that the HH2Read software is set to use that COM port. If a USB to RS232 convertor is being used, please check which COM port has been assigned to it in the device manager (see FAQ 44).
Have you got the right type of RS232 cable? (Delta-T Sales Code HHRS2). The normal RS232 cable has female connectors at each end (and has crossed over lines between some pins). Do not confuse these with RS232 modem cables. Modem cables have male and female connectors (and are wired straight through).
Make sure the HH2 is switched off when communication is attempted
Check what version of HH2read is being used (open HH2 read, click on help, about) and what version of HH2 firmware they are using (switch on the HH2, pres set, scroll to status, press set, scroll to versions, press set, scroll down to see what version the firmware is. It may be that the HH2read softwaremay need updating to the latest version (this can be downloaded from our website, the customer may need to uninstall the current version though – check the readme documents that accompany the installation)
We have noticed that some modern PC's immediately wake the HH2 when they are connected to the PC. Sometimes they are then unable to communicate with the HH2, or communicate inconsistently. The PC's that suffer the problem are different brands (Dell Dimension and Compaq) running Windows 2000. However, other Windows 2000 PC's don't suffer the same problem.
The PC software HH2Read v2 (released March 2002) should improve this situation. But if the problem is encountered, users should be advised not to connect their HH2 before starting HH2Read, and to disconnect it before closing HH2Read.
Note also that if the HH2 is left connected to the closed serial port, it is unable to sleep, and reports that a powered sensor is unexpectedly connected. Disconnect the HH2 from the PC.
BACKGROUND INFORMATIONHH2Read v2 manages the serial port differently from earlier versions, by keeping the serial port open. Earlier versions of HH2Read close the serial port between messages, causing unexpected -9V to +9V transitions, which get confused with the transmitted data and normal communication is then disrupted.
QuestionI see that the environmental protection rating for
Delta-T soil moisture sensors is IP68. In practical terms what does this mean
for the performance of the sensors and their cable connections, and can they be
The IP68 Standard
The IP standard defines the degree of protection against the entry
of water and dust that an instrument has. The first digit corresponds to
performance for dust protection, the second figure for the level of water
resistance. A rating of IP68 means that a device is completely sealed against
dust and that it can withstand complete and continuous submersion in
water. More information on the standard
can be found here: https://en.wikipedia.org/wiki/IP_Code.
When Delta-T develop products for use in the field, we not only
aim to meet the requirements of relevant IP standards, but, where possible, to
surpass them. Our product design and testing aims to establish the highest
performance we can achieve for the sensor and the cable connection.
Sensor sealingDuring the design of the SM150, SM300 and ML3 extensive water
resistance tests were performed with reference to IP68 standards. Thermal shock
tests were also carried out, which involved continuously monitoring the
humidity inside the sensor as it was subjected to temperatures above 100OC
before being plunged into ice cold water. It was demonstrated that, even under these harsh ‘shock’ regimes, the sensors showed no signs of
IntroductionThis note explains some slight but important differences in the design evolution of Access Tubes for Profile Probes, and describes a simple bevelling operation recommended for tubes of older construction.Access Tube Design ChangesSome minor design changes were made to access tubes at the time of the introduction of the PR2 Profile Probe. This advice applies equally to long and short access tubes (types ATL1 and ATS1). The basic dimensions of the access tube have not changed, and Profile Probes type PR1 and PR2 can be used in any access tube. You can distinguish access tubes made for Profile Probes by the shape of the bottom plug. For the PR1 it was conical with a rounded end. For the PR2 it is pointed, as shown in the picture. Installation Warnings!The PR1 access tubes were designed for installation using a hitting block placed in the open end (the mouth) of the access tube. The PR2 access tubes are designed for installation using the Insertion Rod (type AT-ROD1) which applies the driving force to the bottom plug of the access tube. Do not use the PR2 Insertion Rod installation method with tubes of the older PR1 design! You will probably dislodge the bottom plug and destroy the tube. Use only the original hitting block to install this type of access tube.
If you are extracting older access tubes for re-installation in different locations, confirm the type of construction, and use only the insertion method appropriate to that type of tube. Some of the earliest PR2 access tubes were incorrectly manufactured. They were supplied around January to March 2005, and do not have enough adhesion between the bottom plug and the fibre material of the tube. If you cannot see a whitish area of internal grinding in the 2 cm above the bottom plug (see the location in the picture above) then the tube is suspect and should not be used. Delta-T can supply free replacement tubes. Please contact your distributor.
Access Tube Bevel UpgradeA further feature of access tubes introduced since mid 2005 is an internal bevel in the entry to the tube. This significantly improves the ease with which the Profile Probe is inserted into the tube and helps to avoid damage to the rings on the Profile Probe, especially if it is not correctly aligned when inserted into the access tube.The internal bevel is worth applying retrospectively to any access tube that does not already have it. Delta-T can provide a de-burring tool suitable for this operation. It can be used on access tubes whether or not they are already installed in the soil. Please contact your distributor.
Use of the Bevelling ToolIf your access tube does not already have this feature you can quickly create it with the bevelling tool. The desired effect is illustrated in the diagram.In any of the processes mentioned below, avoid fibre composite dust by mopping it up with a damp cloth at all stages. If there is any possibility of inhalation of dust, use a filter face mask before you start the process.First of all inspect the open end of the access tube. The top edge of the tube should be flat and in good condition. If it has been abraded or damaged by use, then use a fine toothed flat file to make it flat and smooth. Apply the bevelling tool (use the pointed end of the tool) to the open end of the access tube. Rotate it carefully by hand for a few rotations to create the desired amount of bevelling. Aim to produce a bevel of not more than half the wall thickness of the tube. Do not overdo this process! This is particularly important on the older PR1 tubes, because the whole of the installation force is transmitted through only the remaining flat area of the tube wall. Remember to clean and dry the inside of the access tube before using the Profile Probe.
The Profile Probe User Manual recommends that you use a Theta Probe (ML2x or ML2) to do a two-point soil-specific calibration.
You need to measure the moisture content of a wet sample of your soil, using the Theta Probe, and then oven-dry the sample and measure its water content once again.
The process is fully described in the Theta Probe User Manual and is also available in a detailed application note available from Delta-T. This should enable you to decide if the possible gain in accuracy is worth the additional effort of the calibration.
If you do not possess a Theta Probe, please contact your distributor or Delta-T for advice. The User Manual is available by email in electronic Acrobat pdf file format (and may be available for download from the Delta-T website).
When installing access tubes, air gaps between the outside of the tube and the soil must be minimised for accurate readings.
The most important thing you can do to ensure accurate readings from the Profile Probe is to minimise air gaps around the access tube. Be careful when augering holes not to create a funnel-shaped hole by waggling the top of the auger, and be prepared to start again if you encounter avoidable stones or roots.
Air gaps can create serious errors in the readings. The Profile Probe is sensitive to the water content of the soil around its pairs of stainless steel rings. This sensitivity is biased towards the soil closest to the rings. Air gaps immediately around the access tube reduce the accuracy of the reading in two ways - firstly the sensors will measure some air instead of moist soil, but also the air gap reduces the penetration of the electromagnetic field into the surrounding soil.
It is virtually impossible to quantify the magnitude of errors from air gaps.
If air gaps are suspected, they can sometimes be diagnosed if the soil moisture content at a particular depth is anomalously low. Also, the reading at that depth may show a diminished range of variation in time, in relation to a known wetting event. However, if saturation and flooding of the soil around the tube occurs, the water content signal may exceed that at neighbouring depths.
After installation of the access tube, air gaps might be expected to close up with natural settlement of the loosened soil. However it is not easy to say how soon, or to what extent, this may occur.
SPN1 Wiring Schematic for DL2eDL2e Logger with LAC1This diagram shows the wiring connections for the LAC1 analogue input card. For use with other cards, please refer to the DL2e Logger User Manual.
SettingsThe example shows the SPN1/BF5 sensor outputs connected to analogue channels 1, 2 and 3 in the DL2e logger. Channel 1 DIP switches near the terminal connector must be set to the OFF (down) position. The SPN1/BF5 is a powered sensor. All analogue outputs should be read using differential channels, for best noise avoidance. The LAC1 input card of the DL2e logger is used in its 15-channel (differential) mode, with the 15-30 slider set to "15". Power warm-up for the sensor is shown routed through relay channel 63. Power from the logger’s own battery is connected to terminal 63 using the internal jumper in the DL2e logger. The cable screen is connected to channel 61- or 62- terminals for electrical screening purposes. These are the digital earth/frame connections of the DL2e, and are also used for the Power 0V return.
Special ConsiderationsRelay Warm-up for Powered ChannelsThe sensor needs a warm-up signal in order to enable the circuitry to produce the output signals. Specify one of the DL2e relay channels 63 or 64, and configure it for the warm-up function with a warm-up time of 1 second.
Total & Diffuse OutputsThe Total & Diffuse analogue outputs are shown connected to channels 1 and 2.
Sun State Output OptionsThe Sun state output is shown connected to analogue channel 3. This uses an analogue channel to produce sun hours data. Analogue channel 3 is configured as a resistance channel (in the 3-wire mode). The precision 10kW resistor (0.1% tolerance) is a load resistor. If you cannot obtain this component locally, please request one from Delta-T tech support. When the sun is present, the switch contact is closed. The load resistor is thus shorted to ground and the channel will read zero ohms. With no sun, the switch contact open circuit, and the resistance reading is 10 kW. By means of special DL2e sensor codes these values can be recorded as sun hours in the logger data.
SPN1 Sensor Codes and Program for the DL2eDL2e sensor codes for the SPN1 are included in the Ls2Win SR5 (or later) release. Please upgrade your PC installation first if it is an earlier service release version.
SPWUse this code for the Total energy (W.m-2) and Diffuse energy (W.m-2) outputs from the SPN1.
SPDSelect this code for the sun state output connected to an analogue channel, using the precision 10kW load resistor (as in the diagram above). This will give readings in sun hours per day. Warning! You must use this code only with a 24h average period. You must start your logging run at the time at which you want your daily total logged (e.g. midnight, or 9 am).
SPHSimilar to SPD, but this will give readings in sun hours per hour. Warning! You must use this code only with a 1h average period. A sample DL2e logger program file (e.g. SPN1xmpl.pg2) which uses the SPW and SPH code is available from Delta-T.BF5 Sensor Codes and Program for the DL2eDL2e sensor codes for the BF5 are included in the Ls2Win SR7 (or later) release. Please upgrade your PC installation first if it is an earlier service release version.
BFPUse this code for the Total PAR (mmol.m-2.s-1) and Diffuse PAR(mmol.m-2.s-1) outputs from the BF5. Note that it has a conversion factor of 0.8 to allow for the use of the resistor attenuator.
BFWUse this code for the Total Energy (W.m-2) and Diffuse Energy (W.m-2) outputs from the BF5. Note that it has a conversion factor of 0.8 to allow for the use of the resistor attenuator.
BFLUse this code for the Total Illuminance (klux) and Diffuse Illuminance (klux) outputs from the BF5. Note that it has a conversion factor of 0.8 to allow for the use of the resistor attenuator.
BFDSelect this code for the sun state output with an analog channel, using the precision 10kW load resistor (as in the diagram above). This will give readings in sun hours per day.Warning! You must use this code only with a 24h average period. You must start your logging run at the time at which you want your daily total logged (eg midnight, or 9 am). Warning! If you occasionally get “noisy” readings reported by the DL2e, change the sensor code Autorange function (A) to Fixed Range (F) in the logger configuration.
BFHSimilar to BFD, but this will give readings in sun hours per hour. Warning! You must use this code only with a 1h average period.
Connecting the HeaterConnect the heater wires to a suitable power supply. In air temperatures below 5°C the heater can consume 1.5A at 12V DC. For extended data logging in cold climates, we recommended that you power the heater via a 12 V supplypowered from the mains. Protect the heater power supply from moisture.Take particular care to check that all ground and 0V connections to the various devices attached to the sensor at any time do not create earth-loops. Refer to the sensor user manual for further guidance on this issue.
IntroductionEach WET Sensor has always been supplied with its own individual calibration file. Originally this electronic file was supplied on floppy disc media. Since the introduction of CD media with the WET-2 Sensor, an additional calibration file has been routinely included to cover an extended range of conditions. The extended calibration file improves the accuracy of soil moisture readings taken in higher levels of conductivity and soil moisture. This document explains when to use the extended calibration file.
Identifying Calibration FilesThe standard WET calibration file is named WETnnnnn.cal where nnnnn is the serial number of the WET Sensor (e.g. 27068: batch 27 number 068). The extended range WET calibration file is named WEXnnnnn.cal
Recommended UseThe expected accuracy envelope of the WET sensor over a range of different pore water conductivities and soil moisture contents is given in the WET Sensor User Manual v1.4, pp21-23. The recommendation is as shown in the diagram. It applies to the organic soil setting and also to additional horticultural and artificial substrates (available as WET-GH, -ST, and former -CL upgrades). Use the extended range calibration only for readings that fall in the region indicated. Readings that fall in the standard region can be taken with the extended calibration, but they may incur somewhat larger errors of soil moisture than with the standard calibration. If the standard calibration is used in the extended region, soil moisture values can be significantly in error.
AvailabilityWET Sensor extended calibration files on CD were introduced from WET-2 batch 26-070. If you have lost your files please contact Tech Support by email with the serial number of your WET sensor and we can email them to you.
This can sometimes happen if the battery connector terminals are accidentally shorted out when changing the battery or if the user takes longer than 30seconds to replace the battery. If this happens the HH2 is cold booted, the memory is erased and the factory default settings are restored.
You will need to re-load the WET calibration file back onto the HH2:
Once the file has been loaded back on, please select the WET sensor device option in the HH2:
You should now be ready to take readings again.
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