HOBO MX801 Submersible Logger Quick Start Guide

Overview

The HOBO MX801 Submersible Logger is designed for logging water parameters such as temperature, conductivity, and depth with compatible HOBO W-Series sensors. The logger must be deployed with sensors attached as it is not waterproof without them. A 2-sensor adapter is required if using two sensors.

The following steps outline the process for configuring and deploying the logger:

1. Connect a Sensor
2. Calibrate the Sensor
3. Configure Your Logger
4. Deploy the Logger
5. Download Your Data
6. Process the Data

Note: For W-CTD or W-CT sensors not previously submerged, it is recommended to attach the sensor to the MX801 logger and soak it in tap water for 24 hours before performing a conductivity calibration.

Connect a Sensor to the Logger

1. Remove the rubber cap from the end of the logger.
2. Align the alignment pin on the sensor with the hole on the logger connector to connect the sensor. Avoid forcing the connection to prevent bending pins.

Note: Ensure o-rings and cable connector surfaces are free of debris during assembly to prevent leaks and logger failure.

To attach the tapered coupler:

1. Ensure the magnetic fob is attached to one half of the tapered coupler.
2. Snap one side of the coupler over the connection between the sensor and logger, with the tapered end facing the sensor.
3. Slide the other half of the coupler over the connection and press the parts together until they snap.
4. Tighten the coupler screws using the provided allen wrench. The magnetic fob may need to be moved aside.
5. Insert the magnetic fob into its designated spot on the coupler.

Download and Open HOBOconnect

HOBOconnect is required for use with HOBO MX Series loggers. Download it from: www.onsetcomp.com/products/software/hoboconnect

Calibrate the Sensor

For conductivity, CTD, or DO sensors, calibration should be performed in a lab or office before logger deployment. The HOBOconnect app provides basic calibration steps. For optimal accuracy, consult the sensor calibration sections in the HOBO MX800 Series User's Guide.

Configure Your Logger

Logging Water Level Requires Barometric Pressure

If using the MX801 logger with a CTD sensor for water level measurement, deploy a nearby barometric pressure logger (within 10 miles) to record pressure changes. A HOBO MX802 logger or HOBO MX2001 logger can be used for this purpose, requiring a cable and sensor or a termination plug (W-PLUG) on the MX802 for weatherproofing. HOBOconnect uses this barometric data with CTD pressure data to calculate water level.

To configure the barometric pressure logger using HOBOconnect:

1. Wake the MX802 logger if necessary using the magnetic fob.
2. Set the Logging Interval and Start Logging settings to match those of the MX801 logger with the CTD sensor. Ensure this logger continues until the CTD logger is stopped or its data is downloaded.
3. Confirm the Barometric Pressure channel is enabled.
4. Refer to the HOBOconnect User's Guide for further details.

Configure and Start the HOBO MX801 Logger Using HOBOconnect

1. Wake the MX801 logger using the magnetic fob if needed.
2. Configure the Logging Interval and Start Logging settings to match the barometric pressure logger.
3. Tap Temperature and ensure it is set to On. For water level recording, also set Absolute Pressure to On. Enable or disable other measurement channels as required. For Specific Conductivity, select the channel and input the temperature coefficient for the deployment environment, which may differ from calibration solution coefficients.
4. Refer to the HOBOconnect User's Guide for further details.

Note: Loggers can calculate and record certain parameters without logging the underlying measurements. For instance, salinity can be logged without logging electrical conductivity and temperature. However, logging basic measurements is advisable for potential later use.

Deploying Your Logger

1. Deploy the MX801 logger at the water site. Refer to the HOBO MX800 Series User's Guide for mounting recommendations.
2. If logging water level, deploy the barometric pressure logger.
3. Allow the MX801 logger to reach temperature equilibrium and record a reference water level reading along with the time. This reading is needed for post-processing data in HOBOconnect.

Download the Data

1. At the end of deployment, record critical water parameters and their times for potential data validation and correction.
2. Retrieve the logger from its deployment location.
3. In HOBOconnect, tap the MX801 tile and download the data.
4. If redeploying, clean the sensor if necessary.
5. If a barometric pressure logger was used, download its data using the same device. Process data for both loggers after downloading.

Processing Your Data

1. Select the Data tab.
2. Open the downloaded MX801 data file.

To derive water level, follow steps 3-9:

1. Click the Reference Water Level icon to open the Water Level Assistant.
2. Select a listed Water Density or enter one manually.
3. Check the "Use Reference Water Level" box.
4. Enter the Reference Water Level recorded during deployment.
5. Select the date and time closest to the Reference Water Level measurement.
6. Select the barometric pressure data file or enter a fixed pressure.
7. Click "Proceed" to have HOBOconnect calculate the water level data channel. Export the data file to save the water level and barometric pressure data.

Files can be exported and shared (sharing is available on the mobile app). Dissolved oxygen (DO) data can be processed with nearby conductivity logger data for salinity-adjusted DO or percent saturation DO using barometric pressure data. Refer to the HOBO MX800 Series User's Guide for more information.