HOBO U20 Water Level Logger Manual
1-800-LOGGERS 4
www.onsetcomp.com
4.
Launch the logger. See the
HOBOware User’s Guide
for
details.
•
Make sure both
Abs. Pressure
and
Temperature
are
selected (temperature is required for temperature
compensation of pressure).
•
Logging Battery Voltage
is not essential since you can
check the battery voltage using the Status screen at
launch or readout of logger.
Connecting the Logger to a Computer
The HOBO Water Level Logger requires a coupler (COUPLER2-B)
and USB Optic Base Station (BASE-U-4) or HOBO Waterproof
Shuttle (U-DTW-1) to connect to the computer.
1.
Follow the instructions that came with your base station or
shuttle to attach the base station or shuttle to a USB port
on the computer.
2.
Unscrew the black plastic end cap from the logger by
turning it counter-clockwise.
3.
Attach the coupler to the base station or shuttle
4.
Insert the logger into the coupler with the flat on the logger
aligned with the arrow on the coupler label. Gently twist
the logger to be sure that it is properly seated in the coupler
(it should not turn).
NOTE
: If you are using the Waterproof Shuttle, 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).
Deploying the Logger
The HOBO Water Level Logger is designed to be easy to deploy
in many environments. The logger uses an absolute pressure
sensor, so no vent tube is required. 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
Full Temperature Equilibrium
The pressure sensor is temperature compensated over the
range of 0° to 40°C (32° to 104°F). To obtain the highest level of
accuracy, the logger should be allowed to come to full
temperature equilibrium (approximately 20 minutes) before
the reference level is recorded.
Sudden Temperature Changes
Sudden temperature changes should be avoided. When
deploying a HOBO Water Level Logger for barometric pressure
reference, some consideration should be made to minimize the
rate of temperature fluctuations. Ideally, the barometric
pressure reference logger should be hung several feet below
ground level in an observation well where ground temperatures
are stable (while making sure the logger remains above the
water level). If that is not possible (or if a well is not used), try
to put the logger in a location where it will not be subject to
rapid daily temperature cycles.
Venting
When deploying a HOBO Water Level logger in a well, make
sure the well is vented to the atmosphere. Typically, a small
hole can be drilled in the well cap to ensure that the pressure
inside and outside the well is at equilibrium. If this is not
possible, the barometric pressure reference logger should be
used inside the same well.
Wire
Use a no-stretch wire to hang the water level logger. Any
change in length of the wire will result in a 1-to-1
corresponding error in the depth measurement. Always pull-
test a cable prior to deploying a logger in a well to make sure it
does not stretch.
