Delta-T EV2 User Manual

User Manual for
EV2 Evaporation Pan
and Gauge
EV2-UM-3.0
Delta-T Devices Ltd
Copyright
Copyright © 2015 Delta-T Devices Ltd. All rights reserved. Under
the copyright laws this document may not be copied, in whole or
in part, without the written consent of Delta-T Devices Ltd. Under
the law, copying includes translation into another language.
2  Copyright
Contents
Copyright
Contents
2
3
About this document
5
Warnings
5
Introduction and Description
6
Abour Evaporation
6
Siting and installing the Evaporation Pan
7
Installing the Evaporation Sensor
8
Handle with care.
8
Install of the evaporation sensor
8
Assembly
8
Fill pan with water
9
Place the base plate with the sensor into the water.
9
Attach cable to pan rim
9
Connect sensor cable to the logger.
9
Connect breather hose to desiccant tube
10
Installation
11
Mounting the desiccant tube
11
Sensor connections
12
EV2 Calibration
13
Standard calibration
13
Accuracy and resolution
13
Use with a DL2e data logger
14
Requirements
14
DL2e Reference Documents
14
Input Card and Power
14
Wiring Schematic for DL2e connections
15
DL2e logger configuration
15
Create DL2e program for EV2/G sensor type
16
Use with a GP1 Logger
21
Requirements You need a PC running DeltaLINK software v XXX
or later connected via a serial cable to the logger.
21
Wiring
21
Program GP1 logger
21
Contents 3
Use with a GP2 logger
Requirements
Help and documentation
Specifications
EV2/G Evaporation Gauge
Pressure Reference
Desiccant Capsule
Holder for Evaporation Gauge
EV2/P Class A Evaporation Pan
Maintenance
Pan and sensor
Desiccant
Warranty and Service
Terms and Conditions of Sale
Service, Repairs and Spares
Technical Support
Contact Details:
4  Contents
25
25
25
27
27
28
28
28
28
29
29
29
30
30
31
31
31
About this document
This manual describes how to install the Evaporation Pan type EV2/P and
Evaporation Gauge type EV2/G and use it with a Delta-T data logger.
Refer also to your data logger documents and logging software Help.
Warnings
The sensor contains an exposed pressure diaphragm which is
extremely sensitive and is vulnerable
to damage if overloaded.
When unpacking the gauge it is
important to handle the transmitter
with care.
The aperture at the end of the
sensor is the sensing area and on no
account must this surface be
touched by sharp objects, or any
pressure applied to the face other
than the water pressure which is to
be measured.
About this document 5
Introduction and Description
The evaporation sensor comprises a United States Class A pan
and a high accuracy water level sensor.
Evaporation, recorded as changes in the water level, is measured
by a high accuracy pressure transducer designed to measure
water depths of around 250 mm for use in the standard
Evaporation Pan.
The electrical output signal is linearly related to the depth of
water. The sensor requires a DC voltage power supply.
Regular readings can be made with the use of a Delta-T data
logger. This is typically used to record hourly and/or daily
evaporation rates.
About Evaporation
Evaporation is influenced by temperature, wind speed and
relative humidity. In general, evaporation rates increase with
temperature and wind speed, and decrease at higher humidity.
For the agronomist, evaporation measurement is particularly
important where irrigation demand is being calculated. This is
because plants use more water in conditions favouring high
evaporation, while at the same time less water may be available
for plant growth.
6  Introduction and Description
Siting and installing the Evaporation Pan
The choice of a suitable location depends on the use you have in
mind. But be aware that the World Meteorological Organisation
(WMO) recommend that evaporation stations should be located
at sites which are fairly level and free from obstructions such as
trees, buildings, shrubs or instrument shelters. Such single
obstructions, when small, should not be closer than five times
their height above the pan. For clustered obstructions this
becomes ten times. Plots should be sufficiently large to ensure
that readings are not influenced by spray drift or by upwind edge
effects from a cropped or otherwise different area. Such effects
may extend more than 100 m. The plot should be fenced to
protect the instruments and to prevent animals from interfering
with the water level, but the fence should be constructed in such
a way that it does not affect the wind structure over the pan.
The WMO also recommends that the ground cover at the
evaporation station should be maintained as near as possible to
the natural cover common in the area. Grass, weed, etc. should
be cut frequently to keep them below 7.5 cm for a Class A pan.
Under no circumstances should the instrument be placed on a
concrete slab or asphalt, or on a layer of crushed rock, and the
pan should not be shaded from the sun.
The Class A pan should be supported 3 to 5 cm above ground
level on an open-frame wooden platform which permits air
circulation under the pan, keeps the bottom of the pan above the
level of water on the ground during rainy weather, and enables
the base of the pan to be inspected without difficulty.
The pan is filled to 5cm below the rim (called the reference level).
Siting and installing the Evaporation Pan 7
Installing the Evaporation Sensor
Handle with care
The evaporation sensor is a very sensitive pressure transmitter
which, when used correctly, will measure water pressure to a
depth of 250mm to better than ± 1 mm. When unpacking it is
important to handle the transmitter with care. The aperture at
the end of the sensor is the sensing area and on no account must
this surface be touched by sharp objects or any pressure applied
to the face other than the water pressure which is to be
measured.
Install the evaporation sensor
During the installation of the evaporation sensor it is important to
follow these procedures:
Assembly
Clamp
screw
Without touching the sensitive circular diaphragm in the base of
the sensor, carefully place the sensor into the hole in the base
plate. Ensure that the sensor body does not protrude through the
hole but is flush with the base plate (see figure).
Use the hexagonal Allen key supplied to carefully adjust the
clamping grub screw used to hold the sensor in the required
position.
DO not over tighten the clamp screw as this could damage the
sensor. Only tighten it enough to secure the sensor.
8  Installing the Evaporation Sensor
Fill pan with water
Fill the evaporation pan to approximately 50 mm from the top
edge.
Note: it is recommended to keep the pan topped up to 50 mm
from the top edge for optimum performance. In countries with
high ambient radiation from the sun the sensor should be kept
submerged as excessive heat could damage the sensor.
Place the base plate with the sensor into the water
Note: it is important to remove any air bubbles from the
underside of the sensor by carefully turning the sensor upside
down under water until all the air has escaped from the cavity in
the sensor.
Attach cable to pan rim
Locate the short thick section of the
cable about 50cm from the sensor.
With the sensor sitting inside the
pan, attach this to the edge of the
pan using the clamp – to hold the
cable secure but do not crush it.
Connect sensor cable to the
logger
Please see the following sections about connecting Delta-T
loggers
DL2e Logger: page 14
GP1 logger: page 21
GP2 logger: page 25
Installing the Evaporation Sensor 9
Connect breather hose to desiccant tube
Drying tube with desiccant
Rubber hose
Connector pipe
Breather hose
The back of the pressure sensor needs to be open to the
atmosphere but it can be damaged by moisture, so it is protected
by a vapour barrier in the form of a tube of desiccant.
Figure 1 showing the desiccant tube as shipped, with flexible
hose and steel connector. Remove the yellow cap at right before
taking readings.
Figure 2 This shows the black tape used to crimp the rubber
tube closed to help preserve the desiccant during shipment.
Remove it when installing.
10  Installing the Evaporation Sensor
Installation
Attach the small rubber tube of the vapour barrier capsule on to
the small plastic tube that protrudes from the sensor wire near to
the connection plug.
Important: remove the yellow plug on the vapour barrier capsule
opposite to the small pipe connected to the sensor pipe.
The capsule is now active and will only allow dry air to access the
sensor.
Mounting the desiccant tube
If possible mount this inside a ventilated weather- proof housing
to protect it from rain or immersion. If installed outside mount it
vertically with the open end pointing downwards.
See also Maintenance on page 29.
Installing the Evaporation Sensor 11
Sensor connections
Wire tails at the free end of the cable are provided for connection
to data loggers or other electronic measuring equipment.
Function
Signal HI
Signal LO
Power V+
Power 0V
Screen
Colour
white
black
red
blue
green (if
present)
Notes:
1.
The Signal LO and Power 0V are connected within the cable.
2.
The cable screen is connected to the metal body of the
gauge, but is not connected to any other wire. It may or
may not be provided with a tail.
3.
A precision 10 ohm resistor is embedded in the free end of
the cable.
12  Sensor connections
EV2 Calibration
Standard calibration
This is derived from the basic 4-20 mA output of the pressure
transducer passing through the precision 10 ohm resistor to
produce a linear millivolt signal output.
mV
0
40
80
120
160
200
mm water
-62.5
0
62.5
125.0
187.5
250.0
For the DL2e, the following values are required:
•
•
Conversion factor: 0.64 (mV per mm)
Offset: – 62.5 (mm)
Accuracy and resolution
The standard calibration values can be used for any EV2/G Gauge.
Using these values, the changes in water level will be accurately
recorded to within a few tenths of a millimetre.
The resolution of readings obtained with a Delta-T data loggers is
0.1 mm.
The absolute depth of water may not correspond exactly to the
depth of water as measured by a ruler, owing to the uncertainty
in the exact position of the pressure sensor diaphragm near the
bottom of the pan. This is not important, since only changes in
level are relevant. However, if you wish to eliminate any
discrepancy, the Offset value shown above can be adjusted.
EV2 Calibration 13
Use with a DL2e data logger
Requirements
Programming the logger requires a PC running Ls2Win, connected
via a serial cable to a DL2e fitted with a LAC1 input card.
DL2e Reference Documents
See also Ls2Win PC software on-line Help and the DL2e Quick
Start, Hardware Reference and Getting Started documents.
These documents are all installed on the PC with Ls2Win and
available from the Start menu, typically under All Program/ DeltaT Devices/Ls2Win/Documents.
Input Card and Power
This example shows the DL2e terminal connections appropriate
for a LAC1 input card, and assumes the DL2e and sensor are
powered by the DL2e’s internal alkaline cells.
14  Use with a DL2e data logger
Wiring Schematic for DL2e connections
–1+
BK
–2+
–3+
–4+
–5+
W
Signal HI (white)
Signal LO (black)
Power V+ (red)
Power 0V (blue)
Screen
GN
BL
Screen (if fitted) to Logger frame
or 61- or 62-
R
– 61 + – 62 + 63 NO NC 64 NO NC
The example shows the wiring of one EV2 Evaporation Gauge to
analogue channel number 1 (for convenience) and assumes:
• The DL2e is powered by its internal alkaline cells.
• An LAC1 input card is used, in its 15-channel mode
• The DL2e internal battery is used to power the EV2 via warmup relay channel 63. The power is returned to channel 62-, the
digital earth (frame) for the DL2e.
The following jumpers/sliders inside the DL2e must be set:
• Power supply selection: jumper set to INTL
• Power to Relay 63: jumper in place
• LAC1 card: 15-30 slider set to "15"
Notes:
 If connected to logger channel 1 ensure the DL2e thermistor
is switched off. Alternatively, connect to another channel.
 The cable screen wire (when fitted) is connected to either
channel 61- or 62-, the logger’s digital earth (frame) for
electrical screening purposes.
DL2e logger configuration
When you have decided which channel to connect your
Evaporation Gauge to, and which relay channel you will use, you
are ready to start.
You will need to refer to the DL2e User Manual to do this.
Use with a DL2e data logger 15
You can select any analogue channel, but for the LAC1 input card
you must use the 15-channel mode with differential input (not
the 30-channel mode). Either relay channel (63 or 64) can be
used for the warm-up function.
Create DL2e program for EV2/G sensor type
On a PC running DL2 Program Editor select File, New :
Set the Input Card Type to LAC1, 15 channel.
Right click on Channel 1
16  Use with a DL2e data logger
Select Edit Channel to open the Channel Properties dialog and
on the Input Channel tab, for Sensor Type select “Evaporation
Gauge type EV2/G” from the drop down list:
Under Timed Logging set Sample every and Record every to an
appropriate period, say 1h.
Use with a DL2e data logger 17
Click on the Measurement tab to inspect the default settings for
this sensor type:
Click on OK and observe that the row corresponding to channel
one is now populated with the correct settings.
18  Use with a DL2e data logger
Note also the Applications Note window describing the sensor
wiring configuration and with simple instruction about how to set
up and use the sensor.
Select the Ch63-64 tab and double click on the row for Ch63 to
bring up the Channel 63 Properties dialogue and select Warmup
Use with a DL2e data logger 19
On the Warmup tab select Duration and repeat period to suit
channels and check the channel tick box and click OK.
Select File, Save to save a copy of the program to your PC and
File, Send to DL2 to download the program onto your DL2e
logger.
Summary: In this example your DL2e logger, with a LAC1 input
card in 15 channel (differential voltage) mode, is now wired up to
the evaporation pan sensor via channel 1 and configured to read
it every hour, providing “warm-up” power to the sensor for 1s via
channel 63 from the logger’s internal batteries.
(For optimum accuracy use a 10s warm-up time.)
At this point it might be worth temporarily changing the program
to read once every 10s in order to check the device is working OK.
For further guidance see the DL2 logger documentation and Help
as described on page 14.
20  Use with a DL2e data logger
Use with a GP1 Logger
Requirements
You need a PC running DeltaLINK, connected via a serial cable to
the logger.
Wiring
See Sensor connections on page 12
Program GP1 logger
With DeltaLINK running, select File, New Program, and chose the
Standard GP1 Program and press OK.
Use with a GP1 Logger 21
…to display the following:-
Right click on Ch1 and select Edit:
22  Use with a GP1 Logger
This should open the Channel Properties dialog.
Populate the fields as shown below and click OK
Use with a GP1 Logger 23
Under Program Options specify a Recording rate: e.g. 1 hour or 1
day.
Select each of the other channels in turn and use right click, Clear
or simply press Delete on the keyboard to clear them.
Click on File, Send to Logger to send the program to a connected
GP1.
To check it runs OK click Change on the Program tab and
temporarily change to a quicker recording rate e.g. 2s (or 10 s if
you are using the 10s warmup). Click Apply and then select the
Sensors tab and select Read Now.
This should display a graph of the water depth vs time, and so
allow you to quickly determine if everything is working OK.
Note: if using a 10s warmup time the first readings when using
Read Now will show #NAN (Not A Number). This will persist until
first set of 10s is complete.
When you are ready, change it back to the longer- e.g. hourly or
daily recording rate and start the logger running from the Logger
tab in the normal way.
For c help see the DeltaLINK online Help and the GP1 User
Manual
24  Use with a GP1 Logger
Use with a GP2 logger
Requirements
You need a PC running DeltaLINK software connected via a serial
cable to the GP2.
Help and documentation
The online help for the GP2 when running DeltaLINK is
exceptionally useful, as is the GP2 User Manual and the GP2
programming tutorials at www.delta-t.co.uk
With DeltaLINK connected to your GP2 logger (or the GP2
Simulator) select File, New, Program and select the GP2
multifunction program.
Use with a GP2 logger 25
In Measurements click on “Click on to add new item” and select
the EV2/G sensor from the drop down list under Other:
This loads the following default program:
Note in the Info Panel at lower left there is a comprehensive
description of the EV2/G sensor along with a wiring diagram and
instructions on how to configure it.
26  Use with a GP2 logger
Specifications
EV2/G Evaporation Gauge
Submersible pressure transducer
Range
Over-range
Accuracy
Output
Excitation Voltage
0 to 250 mm WG (water gauge)
5 x range
± 1 mm of water depth
(typically ± 0.5 mm)
40 to 200 mV (linear)
7.5 to 28 V dc unregulated
(30 V dc absolute maximum)
22 mA
Maximum supply
current
Recommended warm- At least 1 second (10 s for complete
up
stabilisation)
Operating
0 to 50 °C
temperature range
Storage temperature
-20 to 80 °C
range
Dimensions
Gauge body
50 x 38 mm (height x diameter)
Weight
0.9 kg (including cable)
Cable length
5m
A cable clamp is provided to anchor the cable to the rim of the
pan.
Warning! Do not attempt to shorten the cable. A high precision
10 ohm resistor is embedded in the free end of the cable.
Protect this end of the cable from physical damage.
Specifications 27
Pressure Reference
The reference pressure is provided using an air pipe embedded in
the cable.
Desiccant Capsule
Connected by the air pipe to the back of the sensor, this provides
a vapour barrier to protect the sensor from moisture
Holder for Evaporation Gauge
Dimensions: 30 x 125 mm (height x diameter)
Weight: 1.2 kg
EV2/P Class A Evaporation Pan
Stainless steel USA Class A Evaporation Pan
Dimensions: 254 x 1220 mm (height x diameter)
Weight: 64 kg
28  Specifications
Maintenance
Pan and sensor
To avoid any debris blocking access to the sensor and to help
avoid inducing higher temperatures to the water, it is
recommended that the pan is cleaned out every 3 to 4 months
and the water changed. A clean pan should reflect a high
percentage of radiation from the sun.
Do NOT clean the aperture of the sensor as this could damage the
sensitive pressure transducer.
Desiccant
Inspect the capsule from time to time to see if the silica gel has
turned pink. If this does happen then disconnect the capsule from
the sensor and remove both yellow caps and place in a warm dry
environment at 90°C until the silica gel has changed to blue.
Maintenance 29
Warranty and Service
Terms and Conditions of Sale
Our Conditions of Sale (ref: COND: 1/07) set out Delta-T's legal obligations on
these matters. The following paragraphs summarise Delta-T's position but
reference should always be made to the exact terms of our Conditions of Sale,
which will prevail over the following explanation.
Delta-T warrants that the goods will be free from defects arising out of the
materials used or poor workmanship for a period of twelve months from the
date of delivery.
Delta-T shall be under no liability in respect of any defect arising from fair wear
and tear, and the warranty does not cover damage through misuse or inexpert
servicing, or other circumstances beyond their control.
If the buyer experiences problems with the goods they shall notify Delta-T (or
Delta-T’s local distributor) as soon as they become aware of such problem.
Delta-T may rectify the problem by replacing faulty parts free of charge, or by
repairing the goods free of charge at Delta-T's premises in the UK during the
warranty period.
If Delta-T requires that goods under warranty be returned to them from
overseas for repair, Delta-T shall not be liable for the cost of carriage or for
customs clearance in respect of such goods. However, Delta-T requires that such
returns are discussed with them in advance and may at their discretion waive
these charges.
Delta-T shall not be liable to supply products free of charge or repair any goods
where the products or goods in question have been discontinued or have
become obsolete, although Delta-T will endeavour to remedy the buyer’s
problem.
Delta-T shall not be liable to the buyer for any consequential loss, damage or
compensation whatsoever (whether caused by the negligence of the Delta-T,
their employees or distributors or otherwise) which arise from the supply of the
goods and/or services, or their use or resale by the buyer.
Delta-T shall not be liable to the buyer by reason of any delay or failure to
perform their obligations in relation to the goods and/or services if the delay or
failure was due to any cause beyond the Delta-T’s reasonable control.
30  Terms and Conditions of Sale
Service, Repairs and Spares
Users in countries that have a Delta-T distributor or technical representative
should contact them in the first instance.
Spare parts for our own instruments can be supplied and can normally be
despatched within a few working days of receiving an order.
Spare parts and accessories for products not manufactured by Delta-T may have
to be obtained from our supplier, and a certain amount of additional delay is
inevitable.
No goods or equipment should be returned to Delta-T without first obtaining
the return authorisation from Delta-T or our distributor.
On receipt of the goods at Delta-T you will be given a reference number. Always
refer to this reference number in any subsequent correspondence. The goods
will be inspected and you will be informed of the likely cost and delay.
We normally expect to complete repairs within one or two weeks of receiving
the equipment. However, if the equipment has to be forwarded to our original
supplier for specialist repairs or recalibration, additional delays of a few weeks
may be expected. For contact details see below.
Technical Support
Users in countries that have a Delta-T distributor or technical representative
should contact them in the first instance.
Technical Support is available on Delta-T products and systems. Your initial
enquiry will be acknowledged immediately with a reference number. Make sure
to quote the reference number subsequently so that we can easily trace any
earlier correspondence.
In your enquiry, always quote instrument serial numbers, software version
numbers, and the approximate date and source of purchase where these are
relevant.
Contact Details:
Tech Support Team
Delta-T Devices Ltd
130 Low Road, Burwell, Cambridge CB25 0EJ, UK
email: [email protected]
email: [email protected]
web: www.delta-t.co.uk
Tel: +44 (0)1638 742922
Fax: +44 (0)1638 743155
Service, Repairs and Spares 31
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