Using the Judd Communications Depth Sensor
with the HOBO® RX3000 Station
This application note describes how to connect and operate the Judd Communications Depth Sensor with the
HOBO RX3000 station. The Judd Depth Sensor is compatible with any RX3000 configuration (cellular, Ethernet, or
Wi-Fi) that is equipped with the optional four-channel analog input module. It is suggested that a 6-watt solar
panel be used to ensure that the battery is kept charged properly.
Portions of the Judd Technical Manual are used within this application note, but the full manual is available at
http://juddcom.com/storage/ds2manual.pdf and should be read and understood before attempting to use this
device with the RX3000 station. The Judd Depth Sensor is available in both 0-2.5VDC or 0-5VDC analog output
configurations.
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Care should be taken to minimize the distance between the sensor and the snow surface to reduce error caused by
temperature stratification through the column of air. The optimal sensor height is the maximum snow depth plus
1.6 feet. For example, if the maximum snow depth expected is 3 feet, then the sensor should be mounted at 3 feet
+1.6 feet, or 5 feet (rounding to the closest foot).
1-800-LOGGERS 2 www.onsetcomp.com
The Judd Depth Sensor comes with a 1/2-inch NPT female pipe fitting for mounting and cable egress. Attaching a 4inch or longer PVC threaded pipe nipple to this pipe fitting allows you to mount the sensor to a horizontal member,
such as the Onset half or full cross-arm via the use of two #36 (1 13/16 - 2 3/4 inch) stainless steel hose clamps
(not included). Electrician’s putty or silicone sealant should be used to seal the end of the nipple where the cable
exits to prevent water/snow ingress.
Onset half or full cross arm
Zip Tie
Sensor cable routed
back to the RX3000
Pipe Nipple
Hose clamps
Be sure that the sensor is mounted plumb and level. For more information on mounting, refer to the Judd Depth
Sensor manual at http://juddcom.com/storage/ds2manual.pdf.
Wiring to the RX000 Analog Sensor Module (RXMOD-A1)
1-800-LOGGERS 3 www.onsetcomp.com
Configuring the RX3000 Station with HOBOlink
In HOBOlink®, click Configure and select Module/Sensor Configuration.
Select the Analog Sensor Module from the menu on the left (Module 1 in this example). Set the logging interval,
sampling interval (if desired), and enable the “Use excitation power” checkbox. Select Warmup and enter 2
seconds and 400 milliseconds. Click Save.
1-800-LOGGERS 4 www.onsetcomp.com
Select the channel with the Judd sensor from the menu on the left (Channel 1 in this example) to configure the
sensor scaling. Select the “Enable this channel” checkbox. Type a label for the snow (such as Judd Snow Depth).
Select the sensor/input type and select the “Enable Scaling” checkbox. Type the scaled units, values, and scaled
measurement type. Click Save. To determine specific raw and scaled values, refer to the next section.
Scaling Calculation
Example:
Height = 50.5 inches
Cable length = 25 feet
50.5 + (0.16 * 25) = 54.5
54.5/98.43 = 0.5537
Height (inches) + 0.16(L)* = Scaled Value 1
*L = length of signal cable in feet
Scaled Value 1
= Raw Value
98.43
Enter the calculated values in the scaling fields in
the HOBOlink Sensor Configuration screen as
shown here.
1-800-LOGGERS 5 www.onsetcomp.com
Troubleshooting
When installed correctly and operated within its limitations, the Judd Depth Sensor can provide accurate and
reliable distance measurements. The following are the most likely causes of erroneous measurements:
• The sensor is not perpendicular to the target surface.
• The target is small and reflects little sound.
• The target surface is rough and uneven.
• The target surface is a poor reflector of sound, such as low density snow (<5%).
• The transducer is obstructed by ice or debris.
• Strong winds are blowing the echo out from under the sensor.
• The sensor is too close to the target. The minimum distance to the target needs to be kept greater than
1.6 feet (0.5 m).
For more information on this sensor, contact Onset at 1-800-LOGGERS (1-800-564-4377) or
loggerhelp@onsetcomp.com. You can also contact Judd Communications at 1-801-424-2889.
1-800-LOGGERS (564-4377) • 508-759-9500
www.onsetcomp.com • loggerhelp@onsetcomp.com
© 2015 Onset Computer Corporation. All rights reserved. Onset, HOBO, and HOBOlink are
registered trademarks of Onset Computer Corporation. All other trademarks are the property of
their respective companies.
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