HOBO® U24 Conductivity Logger (U24-002-C) Manual
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The HOBO U24 Conductivity logger (U24-002-C) measures actual conductivity and
temperature, and can provide specific conductance at 25°C and salinity with the
HOBOware® Conductivity Assistant. This easily deployable, rugged logger is ideal for
environments with relatively small changes in salinity (±5,000 µS/cm), such as saltwater
bays, or to detect salinity events, such as upwelling, rainstorm, and discharge events. This
logger can also be used to gather salinity data when deployed with a HOBO U26 Dissolved
Oxygen logger. An optional U2X Protective Housing accessory (HOUSING-U2X) is available
to further protect the logger, reduce fouling, and simplify mounting in harsh environments.
Specifications
HOBO Conductivity Logger
Model: U24-002-C
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
• Conductivity meter for
calibration measurements
Accessories:
• U2X Protective Housing
(HOUSING-U2X)
• Replacement communications
window protective caps
(U22-U24-CAP)
Measurements Actual Conductivity, Temperature, Specific Conductance at 25°C
Conductivity Measurement
Ranges
Conductivity Calibrated
Range - Temperature Range
Conductivity Extended
Ranges
Temperature Measurement
Range
Specific Conductance
Accuracy (in Calibrated
Range using Conductivity
Assistant and Calibration
Measurements)
Conductivity Resolution 2 µS/cm (typical)
Temperature Accuracy 0.1°C (0.2°F) at 25°C (77°F)
Temperature Resolution 0.01°C (0.02°F)
Conductivity Drift Up to 12% sensor drift per month, 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
Environmental Rating IP68
(calculated), Salinity (calculated using PSS-78, the Practical
Salinity Scale 1978)
Low Range: 100 to 10,000 µS/cm
High Range: 5,000 to 55,000 µS/cm; see Plots A and B on next
page for salinity and specific conductance ranges
5° to 35°C (41° to 95°F)
Low Range: 50 to 30,000 µS/cm
High Range: 1,000 to 55,000 µS/cm
(readings below these ranges reported as 0)
-2° to 36°C (28° to 97°F)
Low Range: 3% of reading or 50 µS/cm, whichever is greater
High Range: 5% of reading, in waters within a range of
±3,000 µS/cm of the calibration point; waters with greater
variation can have substantially greater error (see Plot C)
Monthly start- and end-point calibration should be used with
HOBOware Conductivity Assistant to achieve the specified
Specific Conductance accuracy
one conductivity range; 11,500 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); all
materials are suitable for long-term use in saltwater
The CE Marking identifies this product as complying with all
relevant dire
ctives in the European Union (EU).
16844-G
Specifications (continued)
Plot A: Salinity Range* Plot B: Specific Conductance Range in Saltwater
* The Practical Salinity Scale 1978 (PSS-78) used to calculate salinity is
valid for salinities in the range of 2 to 42 ppt. For salinities outside of this
range, use the measured conductivity and temperature data from the
logger with a calculation appropriate for your salinities.
Plot C: Specific Conductance High-Range Accuracy
HOBO U24 Conductivity Logger (U24-002-C) Manual
Note: The accura
cy of the readings is relative to their proximity to the calibration point. The closer the conductivity reading is to the
calibration point, the higher the accuracy. The calibration point is measured in actual conductivity (not specific conductance), while the
calibrated data is provided in either specific conductance or salinity.
2
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