HOBO U20 Water Level Logger Manual
1-800-LOGGERS 2
www.onsetcomp.com
Specifications (continued)
Pressure (Absolute) and Water Level Measurements U20-001-03 and U20-001-03-Ti (continued)
Resolution
<0.085 kPa (0.012 psi), 0.87 cm (0.028 ft) water
Pressure Response Time (90%)***
<1 second; measurement accuracy also depends on temperature response time
Pressure (Absolute) and Water Level Measurements U20-001-04 and U20-001-04-Ti
Operation Range
0 to 145 kPa (0 to 21 psia); approximately 0 to 4 m (0 to 13 ft) of water depth at sea level, or 0 to 7 m (0 to
23 ft) of water at 3,000 m (10,000 ft) of altitude
Factory Calibrated Range
69 to 145 kPa (10 to 21 psia), 0° to 40°C (32° to 104°F)
Burst Pressure
310 kPa (45 psia) or 18 m (60 ft) depth
Water Level Accuracy*
Typical error: ±0.075% FS, 0.3 cm (0.01 ft) water
Maximum error: ±0.15% FS, 0.6 cm (0.02 ft) water
Raw Pressure Accuracy**
±0.3% FS, 0.43 kPa (0.063 psi) maximum error
Resolution
<0.014 kPa (0.002 psi), 0.14 cm (0.005 ft) water
Pressure Response Time (90%)***
<1 second; measurement accuracy also depends on temperature response time
Temperature Measurements (All Models)
Operation Range
-20° to 50°C (-4° to 122°F)
Accuracy
±0.44°C from 0° to 50°C (±0.79°F from 32° to 122°F), see Plot A
Resolution
0.10°C at 25°C (0.18°F at 77°F), see Plot A
Response Time (90%)
5 minutes in water (typical)
Stability (Drift)
0.1°C (0.18°F) per year
Logger
Real-time Clock
± 1 minute per month 0° to 50°C (32° to 122°F)
Battery
2/3 AA, 3.6 Volt lithium, factory-replaceable
Battery Life (Typical Use)
5 years with 1 minute or greater logging interval
Memory (Non-volatile)
64K bytes memory (approx. 21,700 pressure and temperature samples)
Weight
Stainless steel models: approximately 210 g (7.4 oz)
Titanium models: approximately 140 g (4.8 oz)
Dimensions
2.46 cm (0.97 inches) diameter, 15 cm (5.9 inches) length; mounting hole 6.3 mm (0.25 inches) diameter
Wetted Materials
Stainless Steel models: 316 stainless steel, Viton® O-rings, acetal cap, ceramic sensor
Titanium models: Titanium, Viton O-rings, acetal cap, ceramic sensor
Logging Interval
Fixed-rate or multiple logging intervals, with up to 8 user-defined logging intervals and durations; logging
intervals from 1 second to 18 hours. Refer to the HOBOware software manual.
Launch Modes
Immediate start and delayed start
Offload Modes
Offload while logging; stop and offload
Battery Indication
Battery voltage can be viewed in status screen and optionally logged in datafile. Low battery indication in
datafile.
The CE Marking identifies this product as complying with all relevant directives in the European Union (EU).
* Water Level Accuracy: With accurate reference water level measurement, known water density,
accurate Barometric Compensation Assistant data, and a stable temperature environment.
** Raw Pressure Accuracy: Absolute pressure sensor accuracy includes all sensor drift, temperature,
and hysteresis-induced errors.
*** Changes in Temperature: Allow 10 minutes in water to achieve full temperature compensation of
the pressure sensor. Maximum error due to rapid thermal changes is approximately 0.5%.
Plot A
