Onset U24 Operating Manual

HOBO® U24 Conductivity Logger (U24-001) Manual

The HOBO U24 conductivity logger measures actual conductivity and temperature, and can
provide specific conductance at 25°C with the HOBOware® Conductivity Assistant. These
easily deployable, rugged loggers provide the data you need for monitoring water purity
and the impact of pollutants in fresh water. There is an optional U2X Protective Housing
accessory (HOUSING-U2X) available to protect the logger and simplify mounting in harsh
environments.

Specifications

HOBO Conductivity Logger

U24-001

Included Item:

• Communications window
protective cap

Required Items:

• Coupler (COUPLER2-C) with
USB Optic Base Station (BASE­U-4) or HOBO Waterproof
Shuttle (U-DTW-1)

• HOBOware Pro 3.2 or later with
the Conductivity Assistant 2.1
or later

Accessories:

• U2X Protective Housing
(HOUSING-U2X)

• Replacement communications
window protective caps
(U22-U24-CAP)

Measurements Actual Conductivity, Temperature, Specific Conductance at 25°C

Conductivity Calibrated
Measurement Ranges

Conductivity Calibrated
Range - Temperature Range

Conductivity Extended
Ranges

Temperature Measurement
Range

Specific Conductance
Accuracy (in Calibrated
Range)

Conductivity Resolution 1 µS/cm

Temperature Accuracy (in
Calibrated Range)

Temperature Resolution 0.01°C (0.02°F)

Conductivity Drift Less than 3% sensor drift per year, exclusive of drift from fouling

Response Time 1 second to 90% of change (in water)

Operating Range -2° to 36°C (28° to 97°F) - non-freezing

Memory 18,500 temperature and conductivity measurements when using

Sample Rate 1 second to 18 hrs, fixed or multiple-rate sampling with up to 8

Clock Accuracy ±1 minute per month

Battery 3.6 Volt lithium battery

Battery Life 3 years (at 1 minute logging)

Maximum Depth 70 m (225 ft)

Weight 193 g (6.82 oz), buoyancy in freshwater: -59.8 g (-2.11 oz)

Size 3.18 cm diameter x 16.5 cm, with 6.3 mm mounting hole (1.25 in.

Wetted Housing Materials Delrin®, epoxy, stainless steel retaining ring, polypropylene, Buna

(calculated)

Low Range: 0 to 1,000 µS/cm
Full Range: 0 to 10,000 µS/cm

5° to 35°C (41° to 95°F)

Low Range: 0 to 2,500 µS/cm

Full Range: 0 to 15,000 µS/cm

-2° to 36°C (28° to 97°F)

Low Range: 3% of reading, or 5 µS/cm, and

Full Range: 3% of reading, or 20 µS/cm, whichever is greater, using
Conductivity Data Assistant and calibration measurements

0.1°C (0.2°F)

one conductivity range; 14,400 sets of measurements when using
both conductivity ranges (64 KB total memory)

user-defined sampling intervals

diameter x 6.5 in., 0.25 in. hole)

rubber O-ring, titanium pentoxide (inert coating over sensor)

The CE Marking identifies this product as complying with all
relevant directives in the European Union (EU).

15070-F MAN-U24x

HOBO U24 Conductivity Logger (U24-001) Manual

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.

Do not attempt to open the logger case or sensor housing.
Disassembling of the logger case or sensor housing will cause
serious damage to the sensor and logger electronics. There are
no user-serviceable parts inside the case. Contact Onset
Technical Support at 1-800-LOGGERS (1-800-564-4377) or an
authorized Onset dealer if your logger requires servicing.

Logger case

Communications
window; place the
cap at right over the
window to protect it
during deployment

Do not scratch the sensor face

with a sharp tool.

Sensor housing

Sensor face

Operation

An LED in the communications window of the logger confirms
logger operation. When the logger is logging, the LED blinks
once every one to four seconds (the shorter the logging
interval, the faster the LED blinks). The LED also blinks when the
logger is recording a sample. When the logger is awaiting a start
because it was launched in “Start at Interval” or “Delayed Start”
mode, the LED blinks once every eight seconds until logging
begins.

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.

Communication

To connect the logger to a computer, use either the Optic USB
Base Station (BASE-U-4) or HOBO Waterproof Shuttle
(U-DTW-1) with a coupler (COUPLER2-C).

IMPORTANT: USB 2.0 specifications do not guarantee
operation outside the range of 0°C (32°F) to 50°C (122°F).

To launch and read out the logger in the field, 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, Firmware Version

3.2.0 or later) and a coupler (COUPLER2-C)

• HOBO U-Shuttle (U-DT-1, Firmware Version 1.14m030 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.

Connecting the Logger to a Computer or
Waterproof Shuttle

1.

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. Wipe off any residue or slime from the area of the logger
that will go into the coupler, including the communication
window. This will help the logger slide in and out of the
coupler more easily, and help with communication.

4. 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. 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.

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.

WARNING: Do not leave the logger in the coupler for extended
periods of time. When connected to a coupler, the logger is
“awake” and consumes significantly more power than when it
is disconnected and considered “asleep.” Always remove the
logger from the Optic Base Station or HOBO Waterproof Shuttle
as soon as possible after launching, reading out, or checking the
status to avoid draining the battery.

Launching the Logger

Before deploying the logger in the field, perform the following
steps in the office:

1. Start HOBOware.

2. Connect the logger to the computer as described in the
previous section.

1-800-LOGGERS 2 www.onsetcomp.com