Using the Judd Communications Depth Sensor
with the HOBO® U30 Station
This application note describes how to connect and operate the Judd Communications Depth Sensor with the
HOBO U30 Station. The Judd Depth Sensor is compatible with any U30 configuration (GSM, Ethernet, or WiFi) that
is equipped with the optional two-channel analog input module. It is suggested that a 6-watt solar panel be used
to ensure that the battery is kept charged properly. As with any sensor that is connected to the HOBO U30 Station
optional analog ports, HOBOware® Pro software should be used to properly scale the analog input. This ensures
that both the raw data (the .dtf file) and the data displayed in HOBOlink® represent the data the same way.
Note: Because of the significant load that the Judd device draws from the U30 excitation circuit, any additional
analog input device that may be connected to the remaining analog input port will require an independent power
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 U30 Station. The Judd Depth Sensor is available in both 0-2.5VDC or 0-5VDC analog output
configurations. This instruction is based on the 0-5VDC output configuration. In most cases the 0-5VDC version will
provide the best accuracy and resolution.
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).
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 U30
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 U30 Station
Configuring the U30 Station with HOBOware
With the U30 connected to your computer via the USB port, select Launch from the Device menu, and then click
the button pointed out below to configure the analog port. An alternative method is to select Configure
Modules/Ports from the Device menu, then select the sensor and click Configure. Note: When setting up the
launch configuration for the U30, be sure to select a logging interval 10 minutes or slower to maximize battery life.
Logging intervals faster than 10 minutes can significantly impact battery life.
Complete the following steps:
Scaling Calculation
Height (inches) + 0.16(L)* = Scaled Value 1
*L = length of signal cable in feet
Scaled Value 1
= Raw Value
Enter the calculated values in the Scaling
Parameters section of the Configure Sensor
window as shown here:
Height = 90 inches
Cable length = 25 feet
90 + (0.16 * 25) = 94
94/98.43 = 0.95499
When done configuring your sensor, click the Configure button at the bottom of the Conifgure Sensor window.
Click Start at the bottom of the Launch Logger window if applicable.
Sample HOBOlink data
Sample HOBOware Data
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
© 2014 Onset Computer Corporation. All rights reserved. Onset, HOBO, HOBOware and
HOBOlink are trademarks or registered trademarks of Onset Computer Corporation. All other
trademarks are the property of their respective companies.
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