Judd Communications Depth Sensor User manual

Judd Communications Depth Sensor
Judd Communications
2248 E. Lauri Kay Drive
Salt Lake City, Utah 84124
Phone [phone]
Fax [phone]
E-Mail [email protected]
http://www.juddcom.com
SPECIFICATIONS
Power: +12 to 18 VDC, 50 mA
(maximum sample time 2.6seconds)
Output: 0 to 2.5 or 0 to 5 VDC
Range: .5 to 10 meters (1.6 to 32.8 feet)
Beam width: 22 degrees
Accuracy: ±1 cm or .4 % distance to target
Resolution: 3 mm ( .12 inches)
Temp. range: -40°to + 70°C ( -40°to 158°F)
Size: 8 x 8 x 13 cm (3 x 3 x 5 inches)
Weight: .6 kg (1.3 lbs.)
Mounting: 1/2 inch threaded pipe
Cable length: 7.6 meters (25 feet)
Max. cable length: 304 meters (1000 feet)
Temperature Sensor Accuracy: ±.5°C, -40 to +85°C
Temperature Sensor Resolution: .5°C
INTRODUCTION
The Judd Communications Depth Sensor is an inexpensive solution for remotely measuring snow depth or
water levels. The sensor measures the distance from the sensor to a target. The sensor works by
measuring the time required for an ultrasonic pulse to travel to and from a target surface. An integrated
temperature probe with solar radiation shield, provides an air temperature measurement for properly
compensating the distance measured. An embedded microcontroller calculates a temperature
compensated distance and performs error checking.
Both distance and air temperature can be output as an analog signal between 0 to 2.5 Volts or 0 to 5 Volts.
The depth sensor is user configurable by means of internal dip switches. Several configurations are
possible and allow the depth sensor to work with as many different type of systems as possible.
Accurate measurement of snow depth poses many difficult problems. The Judd Communications Depth
Sensor has proven very effective in measuring snow depth, which makes it well suited for other various
applications.

Judd Communications Depth Sensor, Analog Version
OPERATION
Ultrasonic simply means sound waves that are above the range of human hearing in frequency. The depth
sensor’s ultrasonic ranging system operates at a frequency of 50 kilohertz (50,000 cycles). The key
component of the ultrasonic system is the transducer. The transducer is first used as a speaker to transmit
an ultrasonic pulse, then it is used as a microphone to listen for the pulse after being reflected off a
surface. By measuring the amount of time that it takes the ultrasonic pulse to travel from the transducer to
a surface and back again, a distance can be calculated.
The Judd Communications Depth Sensor outputs an analog signals that are proportional to the distance
and air temperature being measured. Both measurements are output sequentially through a single output.
The output signal has two ranges: 0 to 2.5 Volts or 0 to 5 Volts. The range is selected by a jumper on the
main circuit board. The output signals can be can be scaled using the following multipliers:
Distance:
Scale 0-2.5 Volt Range 0-5 Volt Range
Inches 196.85 inches/Volt 98.43 inches/Volt
Centimeters 500 cm./Volt 250 cm./Volt
Air Temperature:
Scale 0-2.5 Volt Range 0-5 Volt Range
Degrees Kelvin 200 degrees/Volt 100 degrees/Volt
The JC Depth Sensor performs multiple echo processing. Multiple echo processing dramatically
improves the reliability of measurements. For each measurement cycle, two initial measurements are
made. If the difference between the two distances is less than 1 centimeter, then the second sample is
saved, and output. If the difference between the two samples isgreater than 1 centimeter, then the oldest
sample is discarded and another measurement is made and another comparison is made. This retry
algorithm will continue up to a maximum of ten times. When a valid measurement can not made, or no
echo is returned, a value of zero is output. When a zero is output to the digital to analog converter, the
output voltage is typically in the range of 3-5 millivolts.
The speed of sound in air varies with temperature. Graph 1 shows the relation. An accurate air temperature
measurement is required for calculating the speed of sound in air. From this, a correction factor can be
calculated for properly compensating the measured distance. With the air temperature measurement taken
from its built in probe, the JC Depth Sensor outputs a temperature compensated distance.
Speed Of Sound In Air
sos = 331.4(TempK/273)^.5
250
270
290
310
330
350
370
390
-100 -50 050 100
Air Temperature degrees C.
Speed of Sound Meters/Second
Graph 1

Judd Communications Depth Sensor, Analog Version
The JC Depth Sensor has a beam width of 22 degrees. The closest object to the sensor will be detected if
it is within its beam width. The diameter of the cone is equal to .38 multiplied by the height of the sensor
above the target.
When installed correctly and operated within its limitations, the JC 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
SENSOR WIRING
Color Function Datalogger Connection
Red +12V +12V
Black Ground Ground
Clear Shield Ground
Green Sensor Enable 2.5 to 12 V Control Port
White Output High Single or Differential input High*
Brown Output Low Differential input Low*
*When single ended inputs are used, the Brown lead is not used.
SENSOR PROGRAMMING
The following steps show how to make temperature and depth measurements with the JC Depth Sensor.
1. Turn on the sensor by applying a +5 to +12 Volt control signal to the green lead.
2. Wait for 800 milliseconds for the depth sensor to warm up and output a temperature measurement.
3. Sample the Air Temp. output by making a differential voltage measurement between the white (+) and
the brown lead (-).
4. Wait for 1800 milliseconds for the depth sensor to output a distance measurement.
5. Sample the Distance output by making a differential voltage measurement between the white (+) and
the brown lead (-).
6. Reset and turn off the sensor by removing the control signal from the green lead.
PROGRAMMING EXAMPLE
The following programming example shows how a Campbell Scientific CR10 datalogger is programmed
for use with the Judd Communications depth sensor. It assumes that you have a depth sensor connected as
follows:
Datalogger Connection
Red +12V
Black Ground
Clear Ground
Green Control port 1 (C1)
White Differential input channel 3 high (3H)
Brown Differential input channel 3 low (3L)
Blue Not connected

Judd Communications Depth Sensor, Analog Version
* 1 Table 1 Programs
01: 5 Sec. Execution Interval
01: P10 Battery Voltage
01: 1 Loc [:Battery ]
The depth sensor sampling routine works best as a
subroutine. The following command will call
subroutine #1 once an hour.
02: P92 If time is
01: 0 minutes into a
02: 60 minute interval
03: 1 Call Subroutine 1
The following command will allow the user to
activate the depth sensor by pressing the "F1" key
while monitoring the input locations using the
TERM or Graph TERM program.
03: P91 If Flag/Port
01: 11 Do if flag 1 is high
02: 1 Call Subroutine 1
If somebody left the depth sensor on, turn it off
04: P92 If time is
01: 0 minutes into a
02: 60 minute interval
03: 30 Then Do
05: P91 If Flag/Port
01: 11 Do if flag 1 is high
02: 21 Set low Flag 1
End statement terminating IF time then DO command
06: P95 End
--------------------------------------------------
Final Storage, or Output Processing
--------------------------------------------------
One hour output
07: P92 If time is
01: 0 minutes into a
02: 60 minute interval
03: 10 Set high Flag 0 (output)
Send hourly data to final storage
Array ID, Julian day, Time, Air Temp, Depth
Assign an output array ID of 101
09: P80 Set Active Storage Area
01: 1 Final Storage Area 1
02: 101 Array ID or location
10: P77 Real Time
01: 120 Day,Hour-Minute
11: P71 Average
01: 1 Rep
02: 3 Loc Air TempF
12: P70 Sample
01: 1 Reps
02: 4 Loc Depth
13: P End Table 1
--------------------------------------------------
Table 2 not used
--------------------------------------------------
* 2 Table 2 Programs
01: 0.0000 Sec. Execution Interval
01: P End Table 2
-------------------------------------------------
Subroutines
-------------------------------------------------
* 3 Table 3 Subroutines
Assign the depth sensor subroutine a number, note
that this number and the calling number need to be
the same.
01: P85 Beginning of Subroutine
01: 1 Subroutine Number
Turn ON the depth sensor
02: P86 Do
01: 41 Set high Port 1
Wait 0.8 seconds for the sensor to output the
Air Temp.
03: P22 Excitation with Delay
01: 1 EX Chan
02: 80 Delay w/EX (units=.01sec)
03: 0 Delay after EX (units=.01sec)
04: 0 mV Excitation
Air Temp is output in milliVolts, scaled to
Kelvin, and then convert to Celsius.
04: P2 Volt (DIFF)
01: 1 Rep
02: 5 2500 mV slow Range
03: 3 IN Chan
04: 2 Loc [:Air TempC]
05: .2 Mult
06: -273 Offset
Air Temp is also converted and saved in Fahrenheit
05: P37 Z=X*F
01: 2 X Loc Air TempC
02: 1.8 F
03: 3 Z Loc [:Air TempF]
06: P34 Z=X+F
01: 3 X Loc Air TempF
02: 32 F
03: 3 Z Loc [:Air TempF]
The depth sensor needs another 1.8 seconds to make
up to 10 measurements and perform error checking
and temperature compensation.
07: P22 Excitation with Delay
01: 1 EX Chan
02: 180 Delay w/EX (units=.01sec)
03: 0 Delay after EX (units=.01sec)
04: 0 mV Excitation
Distance is output in milliVolts, scaled to
inches, and then converted to depth by subtracting
the distance measured from the reference distance.
Use a multiplier of -.19685 for output in inches
and -.5 for ouput in centimeters.
08: P2 Volt (DIFF)
01: 1 Rep
02: 5 2500 mV slow Range
03: 3 IN Chan
04: 4 Loc [:Depth ]
05: -.19685 Mult Convert to inches
06: 46 Offset Sensor mounted at 46"
Turn OFF depth sensor.
09: P86 Do
01: 51 Set low Port 1
The end of subroutine 1, return to main program
10: P95 End
11: P End Table 3

Judd Communications Depth Sensor, Analog Version
INSTALLATION
When mounting the sensor pay careful attention to the cone of the ultrasonic beam. The beam width is 22
degrees which means that the diameter of the beam will be 39% of the distance to the target, as shown in
Figure 1. This means that after traveling 10 meters the beam diameter will be 3.9 meters. In this example
the sensor would need to be mounted at least half the distance of the beam diameter, or 1.95 meters, away
from the mast. Be careful to avoid obstructed beam paths.
To determine the minimum distance the sensor must be mounted away from the mast use this formula:
Crossarm length = .194 x Height
Depth Sensor Beam Width Examples
Perpendicular to Surface
The JC Depth Sensor must
be mounted perpendicular
to the target surface.
Mounting the sensor at an
angle will result in erratic
and unreliable
measurements.
22 Deg.
Incorrect, obstruction in beam
22 Deg.
Incorrect, mast in beam
Diameter
22 Deg.
Height
Correct, unobstructed path
Right
Wrong!

Judd Communications Depth Sensor, Analog Version
To improve the accuracy of the sensor measurements, mount the sensor as close to the target as possible.
This will minimize errors that are a percentage of the distance measured. However, the sensor can not
measure closer than .5 meters to the target, and should be mounted at least 1 meter away from the target.
MOUNTING
Decide how the sensor will be mounted. Will it be attached to an existing structure or will it be mounted
on a separate stand?
If mounting to an existing structure such as a tower, attach the
depth sensor to a 6 to 8 feet section of 1/2 inch galvanized
threaded water pipe (the same kind available at your local
hardware or plumbing store). For more rigidity, use ¾ inch pipe
with a reducer. The cable should pass through the center of the
pipe unless you have ordered the sensor with the connector
option. Screw the pipe into the sensor being careful not to twist
up the cable. Do not over tighten the sensor to the pipe. When
the sensor is threaded to the pipe you will notice a small gap of
bare threads. This should be covered with electrical tape to
prevent rust. If you ordered the connector option, be sure to
cover both halves of the connector to keep out moisture. The
sensor should be mounted 4-6 feet away from any vertical
supporting structure. A good rule of thumb is 2 feet out, for
every 10 feet the sensor is mounted above the surface. The
mounting should be adjusted so that the transducer is held
parallel to the snow surface. Secure the pipe to the supporting
tower by using U bolts or tower clamps.
Measure the distance from the transducer to the target. Write
this value down, it will be used later when programming the datalogger.
If interval measurements are desired build a stand for the sensor
using the following parts:
Thread the cable through the pipe and have it exit the unused hole
on the T section, unless you have ordered the sensor with the
connector option. Screw the sensor onto the pipe being careful
not to twist up the cable. Do not over tighten the sensor to the
pipe. Once the stand is assembled you will notice four small
areas of bare threads where the pipe and couplers join. These
should be painted or covered with electrical tape to prevent rust.
If you ordered the connector option, be sure cover both halves of
the connector to keep out moisture. Secure the cable to the mast
Sensor mounted on a tower
Sensor mounted on an interval stake
base 3/4 inch plywood 2 X 2.5 feet
threaded pipe base secure to plywood with wood screws,
centered along one side, 6 inches in from the
edge
48 inch 1/2 inch
pipe thread into pipe base
1/2 inch "T" attach to top of pipe
8 inch 1/2 inch pipe attach to T

Judd Communications Depth Sensor, Analog Version
using electrical tape or wire ties. The sensor should be adjusted so that the transducer is held parallel to
the surface of the plywood. The Plywood should be painted with white exterior paint to prevent
weathering.
Note the distance from the transducer to the ground or the plywood. Write this value down, it will be used
later when programming the datalogger.
MAINTENANCE
When properly installed, the JC Depth Sensor should require minimal maintenance. To prevent
condensation, a desiccant pack is located inside the sensor and should be inspected whenever the sensor is
opened. Try to avoid opening the sensor, especially in a humid environment. Feel the desiccant pack to
determine its condition. If the clay granules feel hard and grainy, the desiccant is still dry. If the clay
granules feel soft, they have soaked up moisture and the packet should be replaced. Used desiccant packs
can be reactivated by warming them to 250°F for 16 hours. Replacements can be ordered from Judd
Communications. See the following section for instructions on how to open the sensor housing.
The Solar Radiation Shield on the bottom of the sensor is made of white PVC plastic, and will yellow
after several years of exposure to ultraviolet light. The shield is easily removed by gently twisting it
counter-clockwise to unscrew it. Replacement fittings can be obtained from any plumbing supply store, or
ordered from Judd Communications. Check the shield periodically for discoloration and to make sure that
nest building insects have not taken up residence.
CONFIGURATION
Transducer
Solar Shield
Temp.
Probe
Enclosure
Screws Enclosure
Screws
Sensor bottom view
To open the sensor to change configuration options or replace the desiccant pack, loosen the four Phillips
screws on the bottom of the sensor. The screws are captive and can be loosened, but not removed. Once
the screws are loosened, the sensor bottom can be carefully moved aside revealing the inside of the
sensor. At this point note how the desiccant pack and internal cabling are positioned.
When reassembling the sensor, be careful get cables and desiccant pack back into their original locations.
When placing the sensor bottom back into place make sure that none of the cables will pinched before
tightening the lid screws. The lid will not close if the desiccant pack is not positioned properly. DO NOT
FORCE THE COVER! DOING SO WILL DAMAGE THE CIRCUIT BOARDS!

Judd Communications Depth Sensor, Analog Version
1
2
3
4
DIP
Switches
Off/On
1 2 3
Output
Jumper
Pins 1&2, 0 to 5V
Pins 2&3, 0 to 2.5V
Upper
Board
Nylon Bolt
Nylon Bolt
Lower
Board
JC Depth Sensor circuit board assembly
The sensor output has two ranges 0 to 5 volts and 0 to 2.5 volts. The desired range is selected by a jumper
connecting the pin combinations shown in the circuit board illustration. To access the output range
selection jumpers, remove the nylon bolts that hold the upper circuit board in place. Carefully lift the
upper circuit board out of the way, exposing the lower circuit board.
The four DIP switches can be used to configure the sensor to operate in different modes. The default
setting is OFF for all four switches.
Dip Switch Function (switch ON)
1Free run mode
2Fast free run mode
3Temperature compensation disable
4Hold air temp. output 1 sec. longer
DIP Switch 1
Normally the depth sensor makes one measurement upon power up and then holds the output until it is
powered down. In Free Run Mode, the sensor will make continuous repeated measurements with a pause
of one second between. Only the distance measurement is output In Free Run Mode. Normally, when
using Free Run Mode, the Green Sensor Enable wire would be connected to with the Red wire to +12
Volts so the sensor is enabled continuously. The measurements are made using the error check retry
algorithm so the output is updated every 1.5 to 3.5 seconds.
Free Run Mode is used with systems that need continuous operation. It is also useful when the sensor is
used with a datalogger or control system that can not control the delay between sensor enable and sensor
output measurement.
DIP Switch 2
Fast Free Run Mode works the same as Free Run Mode only the error check retry algorithm is not used.
This allows the sensor to make continuous measurements at a rate of 2 per second. If Temperature
Compensation is turned off (DIP Switch 3), then measurements are made at the rateof 4 per second.
Fast Free Run Mode is used with systems that need quick updates such as robotics and industrial control
operations. This mode can also be used by those who are implementing their own signal processing
algorithms.
DIP Switch 3
Temperature compensation can be disabled by turning ON this switch. With temperature compensation
disabled, the sensor will output a raw distance measurement.
This mode is enabled when a user wants to use an external temperature measurement, for compensation.
To compensate with an external temperature measurement follow these steps:

Judd Communications Depth Sensor, Analog Version
1. Obtain the raw distance measurement from the sensor. (make sure DIP Switch 3 is ON)
2. Get the external temperature measurement.
3. Calculate the Correction Factor. CF = ((Temp C. + 273)/273)^.5
4. Multiply the raw distance by the CF.
DIP Switch 4
600 milliseconds after power up the air temperature measurement will be output, and stay on the output
for at least 200 milliseconds before the output changes over to the distance measurement. Some
dataloggers and control systems do not have the ability to make millisecond resolution delays. When DIP
Switch 4 is turned on, the air temperature measurement is held on the output for an addition second for a
total of 1.2 seconds.
This enables dataloggers and control systems with at least one second delay resolution to obtain the air
temperature measurement.
Normal sensor timing sequence with DIP switch 4 OFF:
0 to 400 ms sensor warm up
400 to 800 ms air temp. output
600 to 2600 ms error checking
2600 ms -distance output
Sensor timing sequence with DIP switch 4 ON:
0 to 600 ms sensor warm up
600 to 1800 ms air temp. output
1800 to 3600 ms error checking
3600 ms -distance output
MISC.
Some control systems and dataloggers want to know minimum and maximum range values instead of scale
multipliers. These values do not denote the actual maximum range of the sensors.
Distance:
Scale Minimum Maximum
Inches 0492.15
Centimeters 01250
Air Temperature:
Scale Minimum Maximum
Degrees Kelvin 0500
WARRANTY
The Judd Communications Depth Sensor is warranted by Judd Communications to be free of defects in
material and workmanship under normal use and service for a period of one year from the date of
shipment. Judd Communications obligation under this warranty is limited to repairing or replacing
defective products. The customer shall assume all costs of removing, reinstalling, and shipping defective
products to Judd Communications. This warranty shall not apply to any Judd Communications products
which have been subjected to modification, misuse, neglect, accidents of nature, or shipping damage. This
warranty is in lieu of all other warranties, expressed or implied, including warranties of merchantability or
fitness for a particular purpose. Judd Communications is not liable for special, indirect, incidental, or
consequential damages.
Products may not be returned without prior authorization. To obtain a Return Materials Authorization,
contact Judd Communications. Phone [phone]
Non-warranty products returned for repair should be accompanied by a purchase order to cover the repair.