HOBO MX Water Level Logger (MX2001-0x) Manual
U.S. and International Sales: 1-508-759-9500 7
www.onsetcomp.com
General Guidelines for Deploying the Logger
•
The absolute pressure sensor is temperature
compensated over the range of 0° to 40°C (32° to 104°F).
The barometric pressure sensor is temperature
compensated over the range of -20° to 50°C (-4° to
122°F). To obtain the highest level of accuracy, both the
sensor end and top end units of the logger should be
allowed to come to full temperature equilibrium
(approximately 20 minutes) before you start the logger
measure the reference level.
•
Sudden temperature changes should be avoided.
•
The sensor face located in the nose cone of the sensor
end needs to be in the water to measure water level.
•
Any change in length of the logger cable 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.
•
To prevent the sensor from moving in currents and to
ensure the support cable is kept straight during
deployment, you may need to add a weight to the
suspension cable just above the sensor or hang a weight
below the sensor. In some cases, you may need to both
add a weight and use a stilling well.
•
Be very careful not to exceed the burst pressure for the
sensor. The pressure sensor will burst if the maximum
depth is exceeded (see
Specifications
). The sensor should
be positioned at a depth where it will remain in the water
for the
duration of the deployment, but not exceed the
rated bursting depth.
•
If the environment where you are deploying the logger is
known to have ants that are attracted to electronics, take
appropriate protective measures to protect the logger,
such as using pesticides. Even though the vent
membrane for the logger’s barometric sensor is
protected with a screen, some ants have eaten through
this screen and the membrane, creating a path for
moisture into the logger.
•
Avoid deploying the top-end unit in direct sun as that can
lead to more rapid temperature swings, which can lead
to more measurement error and possibly hurt logger
reliability.
To deploy the logger:
1.
Make sure the top end is connected to the sensor end with
the water level logger cable as described in
Getting Started
with the Logger
.
2.
Attach any small parts, such as bolts with nuts, before you
go into the field so you don’t risk losing them in the field.
3.
Lower the logger into the well or stilling well.
4.
Use the Onset well cap if it is a 5 cm (2 inch) well.
Otherwise, use a 1/4-inch bolt of sufficient length to span
the well top or washer. Mount the logger as follows:
•
The top end must be above any metal well to ensure
good wireless transmission.
•
Make sure there is access for measuring the water level
in the well. In some cases, such as when using the Onset
well cap, it will be necessary to pull the top end of the
logger out of the well to get a water level meter sensor
into the well.
•
Make sure the logger cannot accidentally fall in the well.
•
If the cable is too long, loop the cable and secure the
cable with multiple zip ties to ensure the loop does not
slip. The looped cable should be tight enough that the
cable can be easily pulled out of the well if necessary, but
it must not bend the cable any tighter than a 1.25 cm (0.5
inch) radius to prevent damage to the cable.
5.
Measure the water level from the desired reference point
(top of pipe, ground level, or sea level) and enter it in the
app. Note that you may need to pull the top end out of the
well to gain access for measuring the water level within the
well. Follow these guidelines for determining the reference
level:
•
To maximize accuracy, allow 20 minutes after deploying
the logger before starting the logger and measuring
water depth to allow the logger to reach temperature
equilibrium with the water.
•
If the well is too small in diameter to measure the water
depth while the logger is deployed, measure the water depth
before deployment, then deploy the logger immediately.
Make sure the
sensor face
(represented by
dashed lines in
this diagram) is in
the water to
measure water
level
10.0 mm (0.39 in.)
