HOBO RXW Water Level Sensor Interface User Guide

HOBO RXW Water Level Sensor Interface User Guide

This sensor interface, which is compatible with the MX2001 suite of sensors, monitors changing water levels in a wide range of applications, including streams, lakes, wetlands, tidal areas, and groundwater. It is designed to work with the HOBOnet (HOBO® RX) Wireless Sensor Network in which data is transmitted wirelessly from the sensor mote across the network to the station and then uploaded to HOBOlink® cloud software. With HOBOlink, you can monitor sensor readings, view graphs, set up alarms, download data, and more.

RXW Water Level Sensor

Models:

• RXW-WL-900 (US)
  RXW-WL-868 (Europe)
  RXW-WL-921 (Taiwan)
  RXW-WL-922 (Australia/NZ)

Included Items:

• Cable ties
• Screws

Specifications

Water Level Sensor

Mote Components and Operation

LEDs : There are two LEDs to the left of the LCD screen. The green LED blinks during the process of joining a network, blinking quickly while the mote searches for a network and then slowly as the mote registers with the network. Once the network registration process is complete, the blue LED blinks at 4 seconds to indicate normal operation. If the mote is not currently part of a network, the blue LED will be off. If the blue LED is on and not blinking, there is a problem with the mote. Contact Onset Technical Support.
Solar Panel Cable : This cable connects the built-in solar panel to the mote circuitry.
Battery Holder: The location where the batteries are installed as shown (see Battery Information).
Calibration Connection Pins: Use these pins to connect a programming tool. See Performing a Soil-Specific Calibration for details.
USB Port: Use this port to connect to the mote to a computer via USB cable if you need to update the firmware (see Updating Mote Firmware).
Button : Push this button for 1 second to illuminate the LCD or 3 seconds for the mote to search for a HOBOnet Wireless Sensor Network to join (see Adding the Mote to the HOBOnet Wireless Sensor Network).
LCD Screen: The mote is equipped with an LCD screen that displays details about the current status. The following example shows all symbols illuminated on the LCD screen followed by definitions of each symbol in the table.

Adding the Mote to the HOBOnet Wireless Sensor Network
The mote must join a HOBOnet Wireless Sensor Network before it can begin measuring water level and transmitting data. This requires that you have access to the RX Station and the mote at the same time; we recommend that you complete these steps before deploying the mote.

Important : If you are setting up a new RX Station, follow the instructions in the station quick start before setting up this mote (go to www.onsetcomp.com/support/manuals/24380- man-rx2105-rx2106-qsg for RX2105 and RX2106 stations or go to www.onsetcomp.com/support/manuals/18254-MAN-QSG- RX3000 for RX3000 stations).

To add a mote to the network using the RX Station:

1. If the LCD is blank on the station, press any button to wake it up.

2. Press the Select button once (the number of smart sensors is displayed above Channels). Press Select again to switch to the module with the manager.

3. Press the Search button (the magnifying glass). The magnifying glass icon blinks while the station is searching.

4. Connect the interface connector to the sensor with the direct-read cable in between as shown here. The end of the cable with the longer housing connects to the interface connector as shown below.

5. Open the mote door and install the batteries if you have not already done so.

6. Press the button on the mote for 3 seconds. The signal strength icon flashes and then cycles.

7. Watch the LCD on the mote.
   
   The green LED blinks quickly while the mote searches for a network to join and then blinks slowly while it completes the network registration. Once the mote has finished joining the network, the green LED turns off and the blue LED then blinks indefinitely while the mote is part of the network.
   
   Note : If the mote cannot find the network or has trouble remaining connected during this process, make sure the mote is in a vertical, upright position and within range of the station.

8. Press the Search button (the magnifying glass) on the station to stop searching for motes.
   If you added more than one more mote to the network, then the total channel count on the station LCD for the manager module represents all measurement channels plus a battery channel for each mote in the network.
   Sensor measurements are recorded at the logging interval specified in HOBOlink, transmitted to the station, and uploaded to HOBOlink at the next connection interval (readout).

Mounting and Positioning the Sensor Node

• Position the sensor node towards the sun, making sure the solar panel is oriented so that it receives optimal sunlight throughout each season. You may need to periodically adjust the position of the sensor node as the path of the sunlight changes throughout the year or if tree and leaf growth alters the amount of sunlight reaching the solar panel.
• Make sure the sensor node is mounted a minimum of 1.8 m (6 feet) from the ground or vegetation to help maximize distance and signal strength.
• Consider using plastic poles such as PVC to mount the sensor node as certain types of metal could decrease the signal strength.
• Place the sensor node so there is full line of sight with the next sensor node. Use a repeater if there is an obstruction between sensor nodes.
• There should not be more than five sensor nodes in any direction from a repeater or the manager. Data from sensor nodes travels or “hops” across the network and may not reach the station if the sensor node is more than five hops away.

Deploying the Water Level Sensor

Warning: Do not suspend anything from the 6-foot cable. The 6-foot cable is not designed to support the weight of the direct-read cable and sensor.

Suspending the direct-read cable and water level sensor

• Option 1 (preferred): Using the long direct-read cable (CABLE-DR-xxx) and a compatible well-cap

Note : If you choose this option, the interface connector is outside of the well.

• Option 2: Using the mounting hole on the endcap

The endcap contains a loop that allows you to use a carabiner (rated to 50 lbs. or greater) or some other reliable method to suspend the interface connector.

Water Level Scaling in HOBOlink
The following sections provide information on how to measure the reference water level and account for water density.

Scenario 1: Setting a Reference Water Level

1. Deploy the water level sensor in water and secure it in position (for example, hang it in a well).

2. Make sure your RX Station is logging and connecting fast enough for you to see the current water depth readings. (Press connect on the RX Station to see the latest logged value).

3. Enable Scaling for the HOBOnet water level sensor. In HOBOlink:
   a. Select Devices, RX Devices, then select your station.
   b. Select the wrench at the top of the page and select Module/Sensor Configuration from the menu.
   c. Select Water Level for the appropriate sensor. On the right side of the page, ensure that Enable Scaling is selected.
   

4. Enter the scaling values:
   a. Enter the Scaled Units: for example meters or feet.
   This should match the units shown in Latest Value, or you will need to adjust the multiplier to convert.
   b. Enter the multiplier in the Multiplier field.

c. Enter 0 in the Offset field for now.
d. Enter the Scaled Measurement Type, for example “Pond Water Level”.

5. Click save and note the Latest Value.

6. Take a reference water level measurement.
   • Note this as a negative number if the water level surface is below the reference point, such as groundwater level referenced to the top of the well ( Figure 1 ).
   • Note this as a positive number if the water level surface is above the reference point, such as the bottom of the stream or the zero on a staff gauge ( Figure 2 ).

7. Calculate the offset, which is equal to the reference water level reading (from step 6) minus the current water depth reading (from HOBOlink in step 5).

8. Enter the calculated offset in the Offset field.

9. Click save.

10. Verify latest value matches the correct water level.
    

Scenario 2: Measuring Water Depth (Figure 3)

1. Ensure the water level sensor is in the air.

2. Make sure your RX Station is logging and connecting fast enough for you to see the current water depth readings. (Press connect on the RX Station to see the latest logged value).

3. Enable Scaling for the HOBOnet water level sensor. In HOBOlink:
   a. Select Devices, RX Devices, then select your station.
   b. Select the wrench at the top of the page and select Module/Sensor Configuration from the menu.
   c. Select Water Level for the appropriate sensor. On the right side of the page, ensure that Enable Scaling is selected.
   (Refer to the screen shot in step 3 of the previous section.)

4. Enter the scaling values:
   a. Enter the Scaled Units: for example meters or feet. This should match the units shown in Latest Value, or you will need to adjust the multiplier to convert.
   b. Enter the multiplier in the Multiplier field.

c. Enter 0 in the Offset field for now.
d. Enter the Scaled Measurement Type, for example “Pond Water Level”.

5. Click save and note the Latest Value.
6. Calculate the offset, which is equal to zero minus the current water depth reading (from step 5).
7. Enter the calculated offset in the Offset field.
8. Click save. Latest value should be zero.
9. Deploy the water level sensor in water and secure it in position (for example, hang it in a well).

*The Multiplier represents the density of the water, which is a function of its salinity. This is equal to 1 divided by the true density of the water in g/cm3  (e.g., 1/1.025 for typical salt water).

General Guidelines

• The absolute pressure sensor in the water level 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 and station should be allowed to come to full temperature equilibrium (approximately 20 minutes) before the reference level is entered in HOBOlink as described in Setting up the Station.

• Sudden temperature changes should be avoided.

• When deploying the water level sensor in a well, make sure the well is vented to the atmosphere. Typically, a small hole can be drilled in the side of the well cap to ensure that the pressure inside and outside the well is at equilibrium. Use the Onset well cap (WELL-CAP-02) if it is a 5 cm (2 inch) well. Otherwise, you will need to find another method of attaching the cable at the top of your well so that the sensor stays in position. The sensor cable includes a Kevlar® strength member so it can support the weight of the sensor and its cable. You can attach a clamp around the cable, such as a hose clamp, but be careful not to damage the cable.

• There is a vent for the barometric sensor on the back of the mote. This vent must not collect water or it will block proper barometric pressure readings. The best way to avoid water collecting is to mount the station vertically.

• 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 sensor cable will result in a 1- to-1 corresponding error in the depth measurement.
  Always pull-test a cable prior to deploying a sensor in a well to make sure it does not stretch.

• If you are deploying the sensor in a lake, river, or stream, you must first build a stilling well to protect it and the cable. A simple stilling well can be constructed with PVC or ABS pipe. A properly constructed stilling well holds the sensor in position and protects the sensor from currents, wave action, and debris. Suspend the sensor in the stilling well so it is always underwater, but not on the bottom to be buried by silt.
  For more information, see the Technical Application Note for How to Build a Stilling Well at:
  https://www.onsetcomp.com/resources/tech-notes/how-to-build-stilling-well

• 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 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.

Updating Mote Firmware

If a new firmware version is available for the mote, use HOBOlink to download the file to your computer.

1. In HOBOlink, go to Devices, then RX Devices, and select the name of your station.
2. On the station page, click Overview and scroll down to Device Information.
3. Click the Wireless tab. This icon appears next to the mote if there is a new version of firmware available.
4. Click the firmware upgrade link. Click Download and save the firmware .bin file to your computer.
5. Connect the mote to the computer with a USB cable (open the mote door and use the USB port to the right of the LCD). The blue LED is illuminated while connected.
6. The mote appears as a new storage device in the computer’s file storage manager. Copy the downloaded firmware file to the new storage device (the mote). The blue LED will blink slowly while the file is copying.
7. After the file is copied to the mote, the LED will stop blinking and remain a steady blue. Eject the storage device from the computer and disconnect the cable from the mote. The firmware installation process will begin automatically on the mote. The blue LED will blink rapidly while the firmware is installed. Once the firmware installation is complete, the LCD symbols return and the mote will automatically rejoin the network.

Notes:

• Mac® users: A message may appear indicating the disk has not ejected properly when disconnecting the mote from the computer. The mote is operational and you can ignore the message.
• If the blue LED turns off abruptly while copying the file or installing the firmware, a problem has occurred. Contact Onset Technical Support for help.

Battery Information

The mote uses two 1.2 V rechargeable NiMH batteries, charged by the built-in solar panel. The quality and quantity of solar light can affect whether the battery is sufficiently charged to last through the night and cloudy periods. Make sure the mote is placed in a location that will receive several hours of sunlight each day. If the mote does not receive enough sunlight to recharge the batteries, the battery life is estimated at 3–4 months. When batteries are regularly recharged, expected battery life is estimated at 3–5 years. Battery life varies based on the ambient temperature where the mote is deployed, the logging interval, the number of tripped alarms, and other factors. Deployments in extremely cold or hot temperatures can impact battery life. Estimates are not guaranteed due to uncertainties in initial battery conditions and operating
environment.
Mote operation will stop when battery voltage drops to 1.8 V. Mote operation will return if the battery recharges to 2.3 V. If the batteries are unable to be recharged, replace them with fresh rechargeable batteries. Note: if you install used rechargeable batteries that together are less than 2.3 V, the mote will not resume operation.

To replace rechargeable batteries:

1. Open the mote door.
2. Remove the old batteries and install fresh ones observing polarity.
3. Make sure the solar panel cable is plugged in.

The mote contacts the network once the new batteries are installed. The green LED blinks during this process while the bars in the signal strength indicator on the LCD cycle from left to right and then the x icon blinks. Once this process is complete, the x icon is removed, the green LED stops blinking, and the blue LED begins blinking instead.

Lithium Batteries
You can use two 1.5 V lithium batteries (HWSB-LI) for operation at the extreme ends of the mote operating range. Lithium battery life is an estimated at 1 year, but varies based on the ambient temperature where the mote is deployed, the logging interval, the number of tripped alarms, and other factors.
Estimates are not guaranteed due to uncertainties in initial battery conditions and operating environment. When using lithium batteries, you must disconnect the solar panel cable because the batteries will not be recharged.

To install lithium batteries:

1. Open the mote door.
2. Remove any old batteries and install the new ones observing polarity.
3. Push in the side tab of the solar panel cable connector and pull the connector out of the cable port.
4. Place the connector in the slot on the inside of the mote door. Make sure the solar panel cables are tucked inside the door so that they do not interfere with the interior seal when the mote is closed.

The mote contacts the network once the new batteries are installed. The green LED blinks quickly while the mote searches for a network to join and then blinks slowly while it completes the network registration. Once the mote has finished joining the network, the green LED turns off and the blue LED then blinks indefinitely while the mote is part of the network.

WARNING : Do not cut open, incinerate, heat above 85°C (185°F), or recharge the lithium batteries. The batteries may explode if the mote is exposed to extreme heat or conditions that could damage or destroy the battery cases. Do not mix battery types, either by chemistry or age; batteries may rupture or explode. Do not dispose of the logger or batteries in fire. Do not expose the contents of the batteries to water. Dispose of the batteries according to local regulations for lithium batteries.

Federal Communication Commission Interference Statement

This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of the following measures:

• Reorient or relocate the receiving antenna
• Increase the separation between the equipment and receiver
• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected
• Consult the dealer or an experienced radio/TV technician for help

This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
FCC Caution: Any changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate this equipment.

Industry Canada Statements
This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and (2) this device must accept any interference, including interference that may cause undesired operation of the device.

To comply with FCC and Industry Canada RF radiation exposure limits for general population, the logger must be installed to provide a separation distance of at least 20cm from all persons and must not be co-located or operating in conjunction with any other antenna or transmitter.

NCC Statement

Translation:

Article 12
Without permission granted by the NCC, any company, enterprise, or user is not allowed to change frequency, enhance transmitting power or alter original characteristic as well as performance to an approved low power radio-frequency device.

Article 14
The low power radio-frequency devices shall not influence aircraft security and interfere with legal communications. If found, the user shall cease operating immediately until no interference is achieved. The said legal communications means radio communications is operated in compliance with the Telecommunications Act. The low power radio- frequency devices must be susceptible with the interference from legal communications or ISM radio wave radiated devices.

U.S. and International Sales: 1-508-759-9500
www.onsetcomp.com/contact/support

© 2020–2023 Onset Computer Corporation. All rights reserved. Onset, HOBO, HOBOnet, and HOBOlink are registered trademarks of Onset Computer Corporation. All other trademarks are the property of their respective companies.

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