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 retrieve
HH2Read (old versions)
Ls2win (old versions)

Solution
The 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. \\.\COM10

Note: 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:

1. Make sure there are no mobile phones in the vicinity! When a mobile phone is placed near the sensor head of the AP4 it interferes with the 100MHz excitation signal. This can affect the functionality and therefore the readings taken by it.
   
   
2. Please double check that the "SET RH" value is a similar value to what the ambient reading is (open the AP4 head and wave it around in the air). If the SET value is a lot higher than the actual ambient RH, the readings will never reach the set value and therefore the pump won't switch in and a reading won't be taken (seems like nothing is happening). If the pump is on permanently then it is likely that the air line pipe is disconnected or that the desiccant is worn out.
   
   
3. Try refreshing the desiccant, does it make a difference? Does the pump switch on?
   
   
4. If you are still struggling to get a reading, even with the SET RH set to the ambient conditions, try setting the "SET RH" value in the calibration menu to a value ~5% lower than the ambient reading. If this doesn't solve the problem, try setting the SET RH value to 20%, does the AP4 take readings now?
   
   
5. If it doesn't and you are still experiencing problems, try a reset on the AP4: Press the help button then when the help screen appears, press the shift and "C" keys together. The screen should go blank and the firmware version number should appear, note: this will reset all settings to the factory default values. The AP4 will then start up as normal. Try a calibration and reading run as normal - any change?
   
   
6. Check the difference in temperature between the 2 head thermistors. (Press shift and off together). Once you have viewed it press the EXIT key (unless you want to reset it). This should be no more than +/- 0.5degC. More information on this can be found on page 115 of the AP4 user manual (version3) - this can be downloaded from our website if necessary (www.delta-t.co.uk).
   
   
7. Check the cup seal is ok, ensure the calibration plate is properly sealed against it and protect it from the wind.
   
   
8. Check the calibration plate is clean (no specs of dirt in the holes) and the blotting pad is moist.
   
   
9. Extreme temperatures could cause errors, we recommend that it is not exposed to temperatures >50degC (see p94 of user manual). Also avoid the opposite extreme too – falling temperatures can lead to dew or condensation forming – if you are bringing a cold Porometer into a warm greenhouse, give it time to equilibrate.
   
   
10. When doing the first calibration, allow the head to sit on one of the plate positions (position 3 for example) for 10-15 minutes to let it acclimatise to the current RH. Then do a calibration run on all positions.
    
    
11. Check the barometric pressure you are at when doing the calibration – if you do not have a barometer, use 1000hPa (mbar) at sea level and reduce this by 100hPa for every 1000m altitude.
    
    
12. Is the RH reading stuck on 0% or 99%? If it is only displaying one of these two figures and won’t respond to any RH changes then it is likely to be a circuit board problem within the head. This would need sending back to us for repair.

1. Remove the AP4 from its padded bag
   
2. Unscrew the 4 cross head screws in the bottom of the case:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
3. Pull out the black plastic rivets from the rear of the case and remove the cover, then remove the ribbon cable:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
4. Pull the main chassis out from the black case:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
5. Turn the chassis upside down and unscrew the nut and screw that are highlighted (note: these may be quite stiff to undo)
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
6. Pull off the battery connector from the main PCB:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
7. Push the battery strengthening bracket away from the battery and remove the battery (note: it is a tight fit so it will need some wiggling and some strength to get it out):
   
       
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
8. If the battery is still too snug inside its bracket, try pushing it out from the top. First of all remove the main PCB by pulling out the plastic rivets….
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   …Then by disconnecting the cables that attach to it (please observe anti-static precautions when handling any PCB):
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   …..then push down on the battery to ease it out:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
9. Remove the battery:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
10. To fit a new battery in place, do the same procedure in reverse

Solution:

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:

1. The thermistor bead in the leaf half is embedded in a rubber pad. This can be replaced as a complete unit fairly easily.
2. The cup half thermistor is more difficult to replace and the head may well have to be returned to the factory.

1. These convertors usually come with a driver CD. Please make sure you load the drivers on to your PC, from the CD provided, or from the website specified in the convertor instructions. Then follow all the on screen instructions correctly.
2. Once the drivers have been installed correctly, plug the USB convertor into a USB port on your PC.
3. The computer will then assign the convertor a COM port. You will need to check which com port has been assigned via the computer’s “device manager”:
   
   XP
   Click on Start, Control Panel, System:                         Under the 'Hardware' tab, click on 'Device Manager':
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   Windows 7
   Click on Start, Control Panel, Device Manager:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   Windows 8
   Right click on Desktop background and select 'All Apps'
   
     Right click on control panel and select 'properties':              Click on Device Manager:
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
4. Expand the “ports” option. The example below shows a P.C which has the USB to serial converter installed (COM3):
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
5. Please make sure that you use this same COM port number in the device software e.g. HH2read, SunRead, LS2win, DeltaLINK, AP4 retrieve.
6. You will probably have to re-boot the P.C once the drivers have been installed.
7. Also, please remember to use the original RS232 cable, that was supplied with your device, in series with the RS232 to USB converter.

Problem

Are there any restrictions on upgrading old DL2's to current EPROM and LS2e versions ?

Solution

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.

Problem

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.

Solution

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 peak
ML1 ThetaProbe; 11; Inrush surge limited
EQ1 Equitensiometer; 11; Inrush surge limited
ML2 ThetaProbe; 16; Inrush surge limited
ML2x ThetaProbe; 16; Inrush surge limited
SM200; 16; Inrush surge limited
EQ2 Equitensiometer; 16; Inrush surge limited
PR1/6 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 limited
TVB1 Voltage Regul'r; 2; From TVB1 s/no 930
VP1 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 2001
EQ2; 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

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 NOTE
If 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 sheet
3. 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 point
b)  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.

Action

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 INFORMATION
HH2Read 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.

• Disconnect the ML2 from the logger, so you are just measuring from the bare wires.
• Connect the wires up as follows:
  Red = +ive 9V supply
  Blue = 0v supply
  Green = -ive signal wire to a –ive input on a mV meter
  Yellow = +ive signal wire to a +ive input on a mV meter
• Once connected, power the probe up and see what the mV meter reads when it is held in air (should be 0mV +/-10mV)
• Then insert the theta probe in a bucket of water, the mV meter should read above 1000mV
• During this test ‘wiggle’ the cable and see if the reading changes drastically

• Set it to read mV and check the mV readings in air and water (as above)

Introduction
This 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 Changes
Some 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 Upgrade
A 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 Tool
If 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 DL2e























DL2e Logger with LAC1
This diagram shows the wiring connections for the LAC1 analogue input card. For use with other cards, please refer to the DL2e Logger User Manual.

Settings
The 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 Considerations
Relay Warm-up for Powered Channels
The 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 Outputs
The Total & Diffuse analogue outputs are shown connected to channels 1 and 2.

Sun State Output Options
The 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 DL2e
DL2e 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.

SPW
Use this code for the Total energy (W.m^-2) and Diffuse energy (W.m^-2) outputs from the SPN1.

SPD
Select 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).

SPH
Similar 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 DL2e
DL2e 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.

BFP
Use 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.

BFW
Use 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.

BFL
Use 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.

BFD
Select 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.

BFH
Similar 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 Heater
Connect 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.  

Introduction
Each 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 Files
The 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 Use
The 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.

Availability
WET 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:

• Install the ‘HH2Read’ software on to your computer – you can find this on the ‘Software & Manuals’ CD supplied with the equipment, or you can download it from our website: http://www.delta-t.co.uk/software-downloads.asp  
• The calibration file for the WET sensor is supplied on the CD that comes with the WET sensor (picture of a WET sensor on the CD, with the serial number on). If you don’t have this CD, please let Delta-T tech support know the serial number of the WET sensor (found on the blue label, on the cable) and we’ll send you the cal file via email.
• Connect the HH2 to your PC using the 25w to 9w adaptor and the serial cable (2 separate parts). If your computer does not have a 9pin serial port in the back of it, you will need to purchase a USB to RS232 adaptor. We can provide one of these, if necessary (sales code: USB-RS232), or you can purchase one locally. If you do purchase one locally we recommend that it has an ‘FTDI’ chipset in it, e.g. see ‘EasySync’ convertors - http://www.easysync-ltd.com/product/526/es-u-1001-r10.html.  
• If you have stored any readings since the cold boot, you’ll need to erase the data:
       Turn the HH2 on, press SET, scroll to data, press SET, scroll to erase, press SET, scroll to YES, press
       SET  
• Make sure the HH2 is switched off before trying to communicate with it: 
       Press the ESC key to exit out of the menu structure, then press ESC once more to turn the unit off. 
       Alternatively wait for it to go to sleep automatically after 30 seconds.  
• Run the PC program HH2Read. (You need version 1.82 or later). 
• Select Install, Sensors Calibration, WET Sensor.  
• Insert the CD containing the calibration file, select it via the Open dialogue and press Return. In a few minutes the program should report the calibration file successfully installed.  

Once the file has been loaded back on, please select the WET sensor device option in the HH2:

• Turn the HH2 on ·Press the SET button
• Scroll down to Device
• Press SET
• Scroll down to WET sensor
• Press SET  

You should now be ready to take readings again.