HOBO
®
U20 Water Level Logger
(Part # U20-001-04-Ti)
© 2006 Onset Computer Corporation
Part #: MAN-U20-001-04-Ti, Doc #: 11219-A
Inside this package:
•
HOBO U20 Water Level Logger
•
Calibration certificate
Doc #11219-A, MAN-U20-001-04-Ti
Onset Computer Corporation
Thank you for purchasing a HOBO data logger. With
proper care, it will give you years of accurate and
reliable measurements.
The HOBO Water Level Logger is designed to measure water level in wells,
rivers, streams, lakes, estuaries, and tidal areas. The logger uses a
maintenance-free absolute pressure sensor and features a durable titanium
housing and ceramic pressure sensor. The logger uses precision electronics to
measure pressure and temperature. Using a reference water level, the
HOBOware
®
software automatically converts the pressure readings into
water level readings. Furthermore, the software supports compensation for
temperature, fluid density, and barometric pressure. The logger has enough
memory to record over 21,700 combined pressure and temperature
measurements.
The logger uses an optical USB communications interface (USB-Optic Base
Station, Part # BASE-U-4, with COUPLER2-B) for launching and reading
out the logger. 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.
HOBOware software is also required for logger operation. Visit
www.onsetcomp.com for compatible software.
Specifications
Pressure Sensor
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 - 0.0
7
5% FS, 0.
3
cm (0.0
1
ft) water
Maximum error - 0.1
5
% FS, 0.
6
cm (0.0
2
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
Thermal response time (90%)†
Approximately 10 minutes in water to achieve full temperature compensation of the pressure sensor
* With accurate reference water level measurement and Barometric Compensation Assistant data
** Absolute pressure sensor accuracy includes all pressure drift, temperature, and hysteresis-induced errors
† Maximum error due to rapid thermal changes is approximately 0.5%
Temperature Sensor
Operation range
-20° to 50°C (-4° to 122°F)
Accuracy
0.37°C at 20°C (0.67°F at 68°F), see Plot A
Resolution
0.1°C at 20°C (0.18°F at 68°F) (10-bit), see Plot A
Response time (90%)
3.5 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)
Dimensions
2.46 cm (0.97 inches) diameter, 15 cm (5.9 inches) length;
mounting hole 6.3 mm (0.25 inches) diameter
Weight
Approximately 140 g (4.8 oz)
Wetted materials
Titanium, Viton® o-rings, acetyl cap, ceramic sensor
0
0.5
1
1.5
2
-20
0
20
40
Temperature (°C)
A
cc
ur
a
cy
/R
es
o
lut
io
n (
°C
)
Accuracy
Resolution
Plot A
Shock/drop
Logger is sensitive to shocks. Handle with care and avoid any impact. Always use proper packaging when shipping the logger.
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 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 the relevant directives in the European Union (EU).
