Tech Note
Getting Started

The HOBO MX2001 logger top-end unit (MX2001-TOP) is IP67-rated weatherproof, but should not be considered waterproof. This logger includes an internal barometric sensor for barometric compensation, and for calculating water level data. There is a vent with a hydrophobic membrane that allows the logger to sense barometric pressure while keeping water out. The vent will prevent water intrusion at up to a 1-meter depth for short periods of time; however, care must be taken to keep the vent from being submerged more than 30 minutes.

The vent membrane keeps out most moisture. However deploying these loggers in a continuous, highly-saturated well environment can eventually lead to condensation inside the logger. This can be further worsened by extreme temperature cycling, such as occurs in wells that are in direct sun, and in shallow water tables that are close to the logger.

Adequate air flow is required to ensure condensation is minimized on and around the MX2001-TOP.

Here are some suggestions/options for ensuring adequate ventilation and airflow around the MX2001-TOP:

  • Ensure well cap is not sealed and includes openings to promote cross air circulation
  • Add a ventilated extension pipe to raise the mounting location above grade
  • Deploy the MX2001-TOP outside the well (but not in direct sun)

For wells with sustained levels of high humidity, the barometer vent in the top-end unit must be isolated from the high humidity in the well. One way to do this is to use a rubber grommet to isolate the top section of the MX2001-TOP and add a ventilation area above the grommet as shown in the following illustration. Note that the grommet needs to be tight enough to provide a humidity barrier. Add holes to allow for cross ventilation.

HOBO MX2001 Grommet Well Installation

If your wells must remain sealed or there is no way to avoid a continuous saturated environment, we recommend that you use non-vented water level loggers such as the HOBO U20 or U20L water level loggers.


If your environment is known to have ants that are attracted to electronics, you should take appropriate protective measures such as using pesticides to protect the logger. Even though the vent membrane for the MX2001 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.