This self-directed course will guide you through the basics of how a Groundwater Datalogger is used for taking water level measurements. It also discusses some techniques on how to improve the accuracy of your collected data.

1. GROUNDWATER DATALOGGER
LEVEL MEASUREMENT BASICS
2014 ©HydroG Resources Group Inc.

2. Dataloggers are now frequently used
for water level measurement by
hydrogeologists and technicians.
This course introduces some basic
concepts and methods for beginners.

3. • Introduce basic concepts1
• Review standard
protocols2
• Illustrate practical field
methods3
Course Outline

4. Knowledge Base
We are assuming you are familiar with :
• common terms such as pressure; water
level measurement; elevation; aquifer;
unconfined; water table; etc.
• concepts of quality control and quality
assurance.
For simplicity all our examples deal with the
water table in an unconfined aquifer.

5. BASIC DATALOGGER CONCEPTS

6. What Is A Datalogger?
“Datalogger” is the term used in this
course, however they are also known by a
variety of other terms (including pressure
sensors, transducers, etc).
Dataloggers are available in a wide variety
of makes and models with a large range of
capabilities and associated cost scale.

7. What Is A Datalogger?
Dataloggers allow automated water level
measurements to be obtained at rapid rates
and/or in remote locations. They improve
our capability to monitor water level.
To do this Dataloggers measure water or air
PRESSURE, record those measurements as
digital time series files, and, allows the files
to be retrieved as needed.

8. Why Measure Pressure?
The Datalogger measures pressure, but is
used to obtain water level measurements.
The pressure reading is used as an
INDIRECT measure of water level.
It is important to note that the Datalogger
pressure readings must be CONVERTED to
an equivalent water level measurement.

9. Why Measure Pressure?
• Water pressure increases with depth.
• Pressure values can be converted to an equivalent depth of water.
• However there are a number of practical factors to consider.
we want to measure the
pressure due to water column (PH20 )
water level
but atmospheric air pressure (Patm)
is also acting on the water column
therefore total pressure at this depth PT= PH20 + Patm

10. Datalogger Pressure Measurement
Some Dataloggers have a vent tube to the atmosphere which allow
“Gauge Pressure” measurements of PH2O directly.
Some Dataloggers are sealed units that measure Total (or “Absolute”)
Pressure (PT). In order to obtain PH2O you must also measure Patm (usually
with a separate Barologger) and subtract that value from your readings.
PH20
water level
Patm
PT
Vented Datalogger
Measures PH20 directly.
Non-vented Datalogger
Measures PT
Sensor is open to air pressure
Barologger
Measures Patm

11. Datalogger Construction Basics
• Two component groups to
consider:
1. The pressure sensor, and,
2. The internal electronics
(including battery).
• The pressure sensor has a
diaphragm, one side of
which is exposed to water.
• The diaphragm changes
shape as pressure changes. pressure to
be measured
diaphragm
electronics
(not shown)

12. Datalogger Construction Basics
• The changing shape also changes the electrical
resistance across the diaphragm – this provides a
range of voltage “signals” that corresponds to
equivalent pressures.
• For each measurement the internal electronics
provides voltage to the sensor, then converts the
returning “signal” to a pressure reading, and records
the data.

13. venting and
communication
cable
communication port
Datalogger Construction Example
This is a (very) old example
of a vented sensor.

14. Datalogger Construction Example
electronicspressure sensor
diaphragm
vent tube
Sensor disassembled
to show components

15. Datalogger Type Review
Vented Non-vented
Patm
PatmPH2O
Pconstant
PatmPH2O
diaphragm
atmospheric
pressure
“cancels out”
across diaphragm
PH2O measured
directly
sealed unit
measures PT
PH2O is calculated

16. STANDARD METHODS

17. Standard Method SOP’s
A few datalogger specific Standard Operating
Procedures do exist.
Two examples are:
• USGS
• ISO 2005

18. United States Geological Survey
Use of Submersible Pressure Transducers in
Water-resources Investigations, USGS
Techniques of Water- Resources Investigations
Book 8, Chapter A3 (2004).
Provides a detailed explanation of
theory, and, construction/operation of
Dataloggers.
Please refer to that publication for more
details.

19. ISO 2005
Reference: International Standard ISO/TR
23211, Hydrometry – Measuring the water
level in a well using automated pressure
transducer methods.
 Similar to USGS paper and methodology,
please refer to the publication for more
details.

20. Summary
• Detailed theoretical background information and
SOP’s exist, these deal with a wide variety of
instrument types and conditions.
• However for most practical applications using
modern commercially available complete
Datalogger units, some basic understanding and
common sense use should result in good data.
• We encourage you to develop a practical SOP for
your organization.

21. PRACTICAL FIELD METHODS

22. Try To Avoid These Situations!
(mistakes we have already made, or found, in the field)
confusion
(poor planning)
unanticipated conditions
(that were in fact predictable)

23. (more mistakes ….)
installations that really
don’t measure anything
(can you tell why?)
messy installations
(again, poor planning)

24. Datalogger Success
All of the commercially available Dataloggers that are
typically in use, vented or non-vented, can provide
accurate and valid water level data – provided they are
installed and used correctly.
Operator training is essential for success.

25. Basic Considerations
To ensure you are collecting good (accurate) data, you
should consider a number of factors when using a
Datalogger – including :
• Datalogger choice
• Datalogger use
• Datalogger installation
• Converting Datalogger readings to water levels

26. Datalogger Choice
• Type (Vented vs. Non-vented)
• Measurement range
• Rated accuracy
• Measurement frequency
• Installation method
• Communication method
• Battery life
• Construction material
• Reliability
• Durability
• User options
• Software
• Technical support
• Warranty
• Flexibility
• Special conditions
There are many factors to consider when choosing a
Datalogger for your project. Some of these factors include:

27. Datalogger Choice
The final choice of Datalogger will depend on your
project and organizational needs, specific
recommendations are beyond the scope of this course.
The key is to plan each Datalogger installation starting
with why you need it, what data you need to collect,
what conditions the Datalogger will encounter at the
well, how will it be installed, and, how it will be
maintained and downloaded.

28. Datalogger Use
Once you choose your Datalogger follow the
manufacturer’s instructions regarding
communication, programing and use. In addition you
should:
• Test each Datalogger before it goes into the field.
• Develop a QA/QC program that starts when you
install the Datalogger.
• Regularly maintain / download the Datalogger.
• Review your data – check for errors.

29. Datalogger Use
Remember you are using the Datalogger to calculate
equivalent water level measurements. So you need to
“calibrate” the measurement and conversion process.
• Obtain regular manual water level measurements to
compare to your Datalogger data.
• Check regularly to ensure the Datalogger is responding
correctly to water level change.
• Remember – no Datalogger will last forever, monitor
parameters that predict failure (DRIFT, battery levels,
other anomalies, etc.) before it happens so that you can
replace it in time.

30. Datalogger Installation Basics
The Datalogger is hung
(set) on a cable to a
specific depth in the well
below a reference
(measuring) point.
The depth setting should
be below water and
remain constant .
If needed, the Barologger
is set above the water.
Well Screen
Well casing
Top of well
(measuring point)
Water
Level
Cable
Datalogger
Barologger
(if needed)

31. Installation Considerations
• Depth to water and well construction (e.g. total well depth).
• Expected water level variation (e.g. avoid a dry Datalogger).
• Maximum pressure / depth (exceeding damages the sensor).
• Type of cable used (stainless, direct read, vented, etc.).
• How cable is secured at the top of the well.
• Need for Barologger to measure atmospheric pressure.
• Other equipment installed in well.
There are many factors to consider when installing
your Datalogger. Some of these factors include:

32. Some Installation Tips
• Vented Dataloggers need a Vented
communication cable, install according to
manufacturer’s instructions.
• Direct read cables can also be used for Non-
vented Dataloggers, again install according to
manufacture’s instructions.
• Many Non-vented Dataloggers are installed on
simple cables or lines. These need to be removed
(pulled) from the well at each download.

33. Our Preferred Method
held securely in place
lowered into well
to set depth
stainless
cable
stainless
swage
sleeves
stainless
hose clamp
stainless
quick
links
ready to install

34. Some Installation Tips
Please refer to our website for more details on
recommended cable materials and installation
methods for Non-Vented Dataloggers.
hydrogresources.com

35. CalculationsTop of well
(measuring point)
Water Level
Barologger
measures Patm
Datalogger
Vented
measures PH2O
Non-vented
measures PT
watercolumn(W)
Dataloggerdepthsetting(D)
First find W (length, in metres).
A Vented Datalogger may give you
depth of water directly (m or cm).
For a Non-vented Datalogger
subtract Patm from PT .
Programming your Datalogger to
read in depth of water (e.g. cm of
H2O) makes things easier.
Subtracting W from D gives a
depth to water from the top of the
well. Keeping D constant over time
becomes very important!

36. Data Accuracy
• The accuracy of your Datalogger will be much greater than the
accuracy of your installation depth setting measurement or
manual water levels (used to check the validity of your data)
• Manual water level measurements are generally ±1 cm
• Improving the accuracy of your depth setting measurement is one
of the most important methods to improve your data accuracy
• Avoid the tendency to determine the depth setting based on
Datalogger measurements, measure your depth setting!
• Datalogger depth setting (D) changes over time result in DRIFT
There are many factors that affect the accuracy of
your measurements. Some factors to consider:

37. Like everything – the care you take in your
Datalogger installation and use will be
reflected in the accuracy of your data.
Planning the installation, and recording as
much information as possible in the process,
helps immensely.
There is no substitute for common sense, so
adapt to your own situation, and good luck!

38. Response tests are
completed at two
wells at the same
time using separate
Dataloggers.
When you are trying
to do 10 things at
once…….
Some consistency
helps!

39. WE HOPE YOU ENJOYED THIS
COURSE – PLEASE ALSO SEE OUR
COURSES ON ELIMINATING
DATALOGGER ERRORS
2014 ©HydroG Resources Group Inc.