Hobo U24 User manual

HOBO®U24 Conductivity Logger
(Part # U24-001)
Inside this package:
•HOBO U24 Conductivity Logger (U24-001)
Manual Part #: MAN-U24
Doc#: 13681-B
Onset Computer Corporation
Description
The HOBO U24 Conductivity logger is ideal for
measuring and monitoring the impacts of pollutants such
as road salt, agricultural runoff, chemical spills, and salt
water intrusion on water supplies and aquatic ecosystems.
Conductivity is a measure of water’s ability to conduct
electrical current, which is effected by pollutants,
especially those containing inorganic dissolved solids. The
purer the water is, the lower the conductivity. Continuous
monitoring of conductivity at multiple sites along a stream
or in a well will determine when and where spikes of high
conductivity occur, with the goal of identifying the sources
of contamination that caused the high conductivity.
Software
HOBOware®Pro Version 3.0 or above
Communication
To connect the logger to a computer you can use:
•Optic USB Base Station (BASE-U-4) with a
coupler (COUPLER2-C), or
•HOBO Waterproof Shuttle (U-DTW-1) with a
coupler (COUPLER2-C)
To launch and read out the logger in the field you can use
one of these methods:
•Laptop computer with Optic USB Base Station
(BASE-U-4) and a coupler (COUPLER2-C)
•HOBO Waterproof Shuttle (U-DTW-1) and a
coupler (COUPLER2-C).
•HOBO U-Shuttle (U-DT-1, Firmware Version
1.12m030 or later) with Optic USB Base Station
and coupler (COUPLER2-C).
The optical interface allows the logger to be offloaded
without breaking the integrity of the seals. The USB
compatibility allows for easy setup and fast downloads.
LED
A light (LED) in the communications window of the
logger confirms logger operation. The following table
explains when the logger blinks during logger operation:
When: The light:
The logger is
logging Blinks once every one to four seconds (the shorter the logging
interval, the faster the light blinks).
Blinks when logging a sample.
The logger is
awaiting a start
because it was
launched in “Start
At Interval” or
“Delayed Start”
mode
Blinks once every eight seconds
until logging begins.
Sleep Mode
The logger consumes significantly more power when it is
“awake” and connected to a base station or shuttle. The
logger will go into a low-power (sleep) mode if there has
been no communication with your computer for 30
minutes. To wake up the logger, remove the logger from
the coupler, wait a moment, then re-insert the logger.
Sample and Event Logging
The logger can record two types of data: samples and
events. Samples are the sensor measurements recorded at
each logging interval. Events are independent occurrences
triggered by a logger activity, such as Bad Battery or Host
Connected. Events help you determine what was
happening while the logger was logging.
The logger stores 64K of data, and can record over 18,500
temperature and conductivity measurements.

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Connecting the Logger to a Computer
or Waterproof Shuttle
1. If you are connecting to a computer, follow the
instructions that came with your base station or
Waterproof Shuttle to attach it to a USB port on
the computer.
2. Attach the coupler to the base station or shuttle.
3. Insert the logger into the coupler, aligning the
bump/arrow on the coupler with the arrow on the
logger. Be sure that it is properly seated in the
coupler.
NOTE: If you are using the HOBO Waterproof Shuttle
as a base station with a computer, briefly press the
Coupler Lever to put the shuttle into base station
mode.
If the logger has never been connected to the computer
before, it may take a few seconds for the new hardware to
be detected by the computer.
Important: USB communications may not function
properly at temperatures below 0°C (32°F) or above 50°C
(122°F).
Setup
Before you deploy the HOBO U24 in the field, perform
the following steps in the office:
1. Start HOBOware.
2. Connect the logger to the computer. See
“Connecting the Logger to a Computer or
Waterproof Shuttle” above.
3. Verify Status.
Click STATUS on the toolbar and observe that the
temperature is near the actual temperature.
4. Launch the logger. See the HOBOware User’s
Guide for details.
NOTE: Logging Battery Voltage is not essential since you
can check the battery voltage using the STATUS screen at
Launch or Readout of the logger. Logging the battery
voltage will reduce the number of conductivity and
temperature readings you can log.
Deploying the HOBO U24
The HOBO U24 is designed to be easy to deploy in many
environments. The small size of the logger is convenient
for use in small wells and allows the logger to be mounted
and/or hidden in the field.
Deployment Guidelines
•You will need to use a field conductivity meter to
periodically calibrate the U24 readings. Calibrate
the field conductivity meter before taking it into
the field.
•Make sure the logger is getting a steady flow of
the water that is being monitored.
•If possible, when deploying the logger in rivers,
streams and ponds, insert the logger in a PVC or
ABS pipe. The PVC pipe should have enough
holes to ensure good circulation of water.
•To avoid bubbles collecting on the sensor, make
sure the sensor face is vertical and avoid sudden
temperature changes.
•Do not place any metal within 2.5 cm (1”) of the
sensor.

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Collecting Data
Initial Deployment at Each Site
1. Launch the logger with a laptop or shuttle.
2. Deploy the logger in the stream.
3. Allow enough time for the logger to temperature
stabilize for the best accuracy (approximately 15
minutes).
4. Gently tap the logger to remove any bubbles from
the surface. Tug the string if you cannot reach the
logger itself.
5. Measure the specific conductivity, referenced to
25°C, with the field meter. Record the value, time
and location of that reading in a field notebook. If
you cannot access the water with the meter, use a
bailer or other device to obtain a water sample.
Repeat procedure for each logger deployed.
Field Readout
Your readout and maintenance schedule will be
determined by the amount of fouling at the site.
1. Calibrate the field conductivity meter before using
it to take field readings.
2. Before removing the logger, measure the specific
conductivity with the field meter. Record the
value, time and location of that reading in a field
notebook.
3. Remove the U24 logger from the stream.
4. Read out the data from the logger using a shuttle.
5. Relaunch the logger.
6. Clean the sensor (see Maintenance).
7. Redeploy the logger in the stream.
8. Allow enough time for the logger to temperature
stabilize (approximately 15 minutes).
9. Gently tap the logger to remove any bubbles from
the surface. Tug the string if you cannot reach the
logger itself.
10. Measure the conductivity with the field meter.
Record the value and time of that reading in the
field notebook.
Analyzing the Data
1. Offload the most recent data files from the shuttle.
2. Open the data file for each logger.
3. Calibrate data and convert to specific conductance
or salinity.
For each file, use the HOBOware Pro
Conductivity Assistant to calibrate the readings
and adjust for drift caused by fouling. You will
need to enter the field meter readings and times
from the beginning and, optionally, the end of that
segment of the logger’s deployment.
Refer to the Help for the Conductivity Assistant
for more details.
Maintenance
Cleaning the Sensor
Mix several drops of dish detergent or biodegradable soap
in a cup of tap water with a clean cotton swab. Clean the
sensor face using the cotton swab and then rinse the sensor
with clean or distilled water. Do not scratch the sensor face
with a sharp tool.
Biofouling
Biofouling and excessive marine growth on the logger will
compromise accuracy. Organisms that grow on the sensor
can interfere with the sensor’s operation and eventually
make the sensor unusable. If the deployment area is prone
to biofouling, check the logger periodically for marine
growth.
Solvents
Check a materials-compatibility chart before deploying the
logger in locations where untested solvents are present.
Refer to the Specifications for materials.
Protecting the Logger
IMPORTANT
•This logger can be damaged by shock.
Always handle the logger with care. The logger
may be damaged if it is dropped. Use proper
packaging when transporting or shipping the
logger.

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•Do not attempt to open the logger case or sensor
housing.
Disassembling of the logger case or sensor
housing may cause serious damage to the sensor
and logger electronics. There are no user-
serviceable parts inside the case. Contact Onset
technical support if your logger requires servicing.
The Battery
Battery Life
The battery life of the logger should be three years or
more. Actual battery life is a function of the number of
deployments, logging interval, and operation/storage
temperature of the logger. Frequent deployments with
logging intervals of less than one minute, and continuous
storage/operation at temperatures above 35°C, will result
in significantly lower battery life. For example, continuous
logging at a one-second logging interval will result in a
battery life of approximately one month.
To obtain a three-year battery life, a logging interval of
one minute or greater should be used and the logger should
be operated and stored at temperatures between 0° and
25°C (32° and 77°F).
Battery Voltage
The logger can report and log its battery voltage. If the
battery falls below 3.1 V, the logger will record a “bad
battery” event in the datafile. If the datafile contains “bad
battery” events, or if logged battery voltage repeatedly
falls below 3.3 V, the battery is failing and the logger
should be returned to Onset for battery replacement.
Replacing the Battery
To have your logger’s battery replaced, contact Onset or
your place of purchase for return arrangements. Do not
attempt to replace the battery yourself. Severe damage to
the logger will result if the case is opened without special
tools, and the warranty will be voided.
WARNING: Do not cut open, incinerate, heat above
100°C (212°F), or recharge the lithium battery. The battery
may explode if the logger is exposed to extreme heat or
conditions that could damage or destroy the battery case.
Do not dispose of the logger or battery in fire. Do not
expose the contents of the battery to water. Dispose of the
battery according to local regulations for lithium batteries.
Specifications
Sensor
Conductivity Temperature
Calibrated Range Low Range: 0 to
1,000 µS/cm
Full Range: 0 to
10,000 µS/cm
5° to 40°C (41° to
104°F)
Extended Range Low Range: 0 to
2,500 µS/cm
Full Range: 0 to
15,000 µS/cm
0° to 40°C (32° to
104°F)
Accuracy (in
calibrated range) 3% of reading, or 5 µS/cm, whichever is
greater 0.1°C (0.2°F)
Resolution 1 µS/cm 0.01°C (0.02°F)
Response time 1 second to 90% of change
Logger
Memory
18,500 temperature and conductivity
measurements when using one
conductivity range; 14,400 sets of
measurements when using both
conductivity ranges (64kbytes total
memory)
Sample rate 1 second to 18 hrs, fixed or multiple-rate sampling with up to 8 user-defined
sampling intervals
Battery 3.6 Volt lithium battery
Battery life 3 years (at 1 minute logging)
Maximum Depth 70 m (225')
Operating Range 0° to 50°C (32° to 122°F) - non freezing
Weight 193 gm (6.82 ounces), buoyancy in
freshwater: -59.8 gm (-2.11 ounces)
Size 3.18 cm diameter x 16.5 cm, with 6.3 mm
mounting hole (1.25" diameter x 6.5", ¼”
hole)
Wetted Housing
Materials
Delrin, epoxy, stainless steel,
polypropylene, Buna rubber O-ring,
titanium pentoxide (sensor)
The CE Marking identifies this product as
complying with all relevant directives in the
European Union (EU).
© 2010 Onset Computer Corporation. All rights reserved.
Onset, HOBO, and HOBOware are trademarks or registered trademarks
of Onset Computer Corporation covering its data logger products and
configuration/interface software.
All other trademarks are the property of their respective companies.