The combination of the HOBO Remote Monitoring System/GSM and one or two third-party water level sensors with 4-20mA analog outputs provide a solution to remotely monitor water levels and access data via the internet. This system can also send notifications when critical levels are reached. Typical applications include monitoring wells, groundwater, surface water, stormwater and storm surges. This application note provides details on configuring the HOBO U30 with water level sensors with a 4-20mA output.
Configure the HOBO U30's Analog Sensor Port
Use HOBOware Pro to set up the Analog Sensor Port for the water level sensor before you deploy the logger. Connect the U30 to the computer running HOBOware Pro with the USB cable. Use Configure Modules/Ports under the Device menu to set up the excitation power warm-up time and scaling for your water level sensor. The example below is for a water level sensor with a 0-10’ range and 500ms warm-up. If you are connecting (2) water level sensors, configure the second channel the same way as the first channel. Note that both sensors will share a common excitation power output. Use the Custom Sensor Name menu selection to give each channel a unique sensor name.
Connecting the water level sensor
Before connecting your water level sensor to the U30, make sure that the cable has been routed through openings as needed. Specifically, if the cable needs to go through a well cap, do that before connecting the wires. Also make sure that the cable is coming through one of the cable openings in the bottom of the U30.
Connecting a water level sensor that can operate from 12V power
Connect as shown in Diagram 1.
Configuration with sensors that work with a 12 V power supply.
Connecting a sensor that requires more than 12 volts
Some water level sensors need excitation power higher than the 12 volts the U30 provides. Diagram 2 below shows how to use a 9V battery to boost the 12V excitation of the U30. This configuration requires a 9V battery connector such as Radio Shack Model 270-325, and a diode rated for at least 50mA and 20V, such as a 4148 diode or a 5817 Schottky diode. With a 1 minute logging rate and 30ms warm-up time, a good 9V battery should last for over a year in this configuration. We recommend replacing the battery annually to be safe.
Analog Sensor Port Connections using a 9 V battery to boost the output voltage.
Connect the desiccant cartridge and install weatherproof cable channels
The cable to the sensor needs to go through the large hole in the weatherproof cable channel. There is only one large hole in each cable channel, so the large opening on one is used for the solar panel cable, and the large hole on the other is used for the water level sensor. If your HOBO U30 did not come with two cable channels, we recommend buying the 5-to-10 Input Expander Kit, part number S-ADAPT-X5-10. The vent tube coming out of the desiccant cartridge (not the one going to the sensor) should go through one of the smaller holes in the cable channels. Make sure the vent tube will not be exposed to any rain or splash.
• The desiccant tube is recommended for keeping moisture out of the vent tube for accurate measurements. The vent tube to the atmosphere gets routed through one of the weatherproof sensor cable openings.
• Be sure the wells with the water level sensors have vent holes to the atmosphere.