JEWELL 781 User manual

USER’S MANUAL
MODEL 781 SIGNAL CONDITIONING UNIT
Serial No.________________
850 Perimeter Road
Manchester, NH 03103 USA
Tel [phone]
Fax [phone]
[e-mail]
www.jewellinstruments.com
Copyright ©2013 by Jewell Instruments LLC. All rights reserved.
Document No. B-88-1006, Rev. B

B-88-1006, REV. B
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USER’S MANUAL
MODEL 781 SIGNAL CONDITIONING UNIT
TABLE OF CONTENTS
1.0 General Information .............................................................................................2
1.1 Introduction ...........................................................................................................2
1.2 General Specifications ..........................................................................................2
2.0 Operation..........................................................................................................6
2.1 Using the Controls; Meaning of the Indicators.......................................................6
3.0 Maintenance and Troubleshooting 7
3.1 Routine Maintenance.............................................................................................7
3.2 Determining the Cause of Malfunctions.................................................................8
A Warranty and Assistance ................................................................................9
B Custom Specification for your Equipment...................................................10
C Revision Table................................................................................................12

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1.0 GENERAL INFORMATION
1.1 Introduction:
The model 781 Signal Conditioning Unit (SCU) is a compact module that may be used with all
Jewell Instrument tilt sensors. Internal SCU electronics provide simultaneous excitation of two
electrolytic tilt transducers, and condition the returned signals into two analog DC voltages. The
SCU provides both single-ended and differential outputs on each of its two tilt channels. You
may thus select the output that is best suited for your application.
The SCU also takes temperature readings from a National Semiconductor LM-35 temperature
sensor, providing an analog output proportional to temperature. Temperature is provided as a
single-ended output only.
This manual explains the functions and use of the three control switches on the front panel
of the SCU, and the input and output terminals on the rear panel (Figures 1 and 2). Basic
maintenance and troubleshooting guidelines are given in the last section of the manual.
1.2General Specifications:
INPUT CHANNELS Two Jewell Instrument electrolytic tilt
sensors, one LM-35 temperature sensor
TILT OUTPUT Two channels of single-ended and differential
analog outputs proportional to tilt
OUTPUT VOLTAGE Approximately ±8 VDC (single-ended) and
approximately ±16 VDC (differential)
OUTPUT IMPEDANCE 270 Ohms, short circuit and surge protected
GAIN RANGE Two gains provided, x1 and x10 standard,
other gains available upon customer request
OUTPUT FILTERS Two low-pass integrators. Roll-off = 6 db
per octave. Settling times set to customer
specifications (see Appendix B).
TEMPERATURE OUTPUT 0.1°C/mV (single-ended),
-40°C to +100°C [-40°F to +212°F]
±0.75°C [±1.35°F] accuracy
POWER REQUIREMENTS +11 to +15 VDC, -11 to -15 VDC, 12 mA
typical, 250 mV P/P ripple max.

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EXTERNAL CONNECTIONS Dual screw-terminal barrier strips
TEMPERATURE RANGE -20°C to +70°C [-4°F to +158°F] Operational
-30°C to +100°C [-22°F to +212°F] Storage
HUMIDITY RANGE 0 to 100%, noncondensing & nonsubmersible
SIZE 3.5" x 5" x 8.4" (8.8 cm x 12.7 cm x 21.3 cm)
WEIGHT 2 lbs. (0.9 kg)
MATERIALS Case: painted aluminum

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2.0 OPERATION
2.1 Using the Controls; Meaning of the Indicators:
There are three 2-position control switches on the front panel of the SCU (Figure 1). The first
is the ON-OFF power switch, the second is the HIGH-LOW gain switch, and the third is the
ON-OFF low-pass filter switch. The ratio between HIGH and LOW gain for your SCU is given in
Appendix B, as are the filter time constants corresponding to the ON and OFF filter switch
positions.
There are two terminal strips on the back panel of the SCU (Figure 1). The lower terminal
strip provides the connections to two tilt transducers, and one temperature sensor. The upper
terminal strip provides the input connection for your external power supply, and the connection
for the conditioned output of the tilt and temperature sensors. The names and functions of the
terminal strip positions on the rear panel of the SCU, are listed below:
NAME FUNCTION
SENSOR 1 The three terminal positions (+), (E), and (-) are for the
three lead wires from the first tilt sensor. (E) is the center,
or neutral wire. (+) and (-) are the positive and negative
pick-ups respectively. For color coding of the sensor lead
wires supplied with your SCU, see Appendix B.
SENSOR 2 The three terminal positions (+), (E), and (-) are for the
three lead wires from the second tilt sensor.
TEMP. SENSOR The three terminal positions (T1), (T2), and (T3) are for
the three lead wires from the LM-35 temperature sensor.
For the color coding of the temperature sensor lead wires
supplied with your SCU, see Appendix B.
OUT +1 This is the Sensor 1 output signal. When operating the
SCU in single-end mode, this signal is referenced to
SIG GND. When operating the SCU in differential mode,
this signal is referenced to OUT -1.
OUT -1 The signal carried on this terminal position is the OUT +1
signal multiplied by -1. OUT +1 is referenced to OUT -1
when a differential output is desired.
OUT +2 This is the Sensor 2 output signal. When operating the
SCU in single-end mode, this signal is referenced to
SIG GND. When operating the SCU in differential mode,
this signal is referenced to OUT -2.

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OUT -2 The signal carried on this terminal position is the OUT +2
signal multiplied by -1. OUT +2 is referenced to OUT -2
when a differential output is desired.
TEMP This is the temperature output signal. It is a single-ended
signal, and is referenced to SIG GND.
SIG GND This is the reference ground for the single-ended outputs
of the SCU.
ESD GND This is a separate earth ground used for protection of the
internal SCU circuitry from high-voltage surges. ESD GND
is connected to the internal circuitry by transient surge
absorbers. These absorbers are nonlinear resistors that
change resistance as a function of the applied voltage
(the higher the voltage, the lower their resistance). Their
response time is approximately 50 nanoseconds. For
maximum surge protection, ESD GND should be
connected to an earthed pipe or ground rod.
+12 V Connect +11 to +15 volts DC to this terminal.
PWR GND Connect the power ground (power common) to this
terminal
-12 V Connect -11 to -15 volts DC to this terminal.
3.0 MAINTENANCE AND TROUBLESHOOTING
3.1 Routine Maintenance:
The SCU is rugged and should require no maintenance other than occasional cleaning of the
box with a soft cloth. Keep the SCU and tilt sensor from extremes of heat and cold. Extreme
temperatures unnecessarily stress the electronic components. If possible, keep the SCU and
sensors out of direct sun, because internal temperatures can build up to a level considerably
greater than the ambient temperature.
The SCU is protected from dust and splashes by its rugged aluminum enclosure. The unit is
not waterproof, so never allow it to be submerged, or allow standing water to accumulate inside.
NOTE: WATER DAMAGE TO INTERNAL COMPONENTS VOIDS THE WARRANTY!
Apart from the procedures described below, the SCU is not field-serviceable. Therefore, if you
should encounter problems not described herein, please contact a Jewell Instruments sales
representative at [phone] for assistance.

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3.2 Determining the Cause of Malfunctions:
Although the SCU is not field-serviceable, there are some basic things you can do if you
should encounter problems.
If there is no output when you have connected the tilt sensor to the SCU, first make sure the
terminal screws are tightened securely to the power supply and sensor lead wires. Also, check
the potential, and the polarity of the power supply. Failure to obtain an output signal normally is
the result of lack of power, or a broken wire or connection.
If you have established that the problem is internal to the SCU, and is not a bad connection or
a bad sensor, check the sensor connections to the internal printed circuit board. To do this, first
remove the top two screws in each side panel then gently lift away the SCU top panel. Small
plastic connectors are used to attach the tilt and temperature sensor leads to the printed circuit
board. Check to be sure that these connectors have not become loose or detached. If you
remove any of these small plastic connectors, be sure to replace the Sensor 1, Sensor 2, and
temperature connectors exactly as you found them. Figure 2 shows the proper connector
locations. CONNECTING THE TILT SENSOR WIRES TO THE TEMPERATURE POSTION ON
THE PCB will cause PERMANENT TILT SENSOR DAMAGE that is not cover by the warranty.
If an inspection of the connections to the printed circuit board does not correct the problem,
please call a Jewell Instruments sales representative at [phone] for assistance.
CAUTION
NEVER USE AN OHMMETER TO MEASURE JEWELL INSTRUMENTS TILT
SENSORS. APPLYING DC CURRENT THROUGH THE SENSORS WILL CAUSE
PERMANENT DAMAGE THAT IS NOT COVERED BY THE WARRANTY

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APPENDIX A - Warranty and Assistance
Jewell Instruments tilt sensing instrumentation is warranted against defects in materials and
workmanship for one year from the date of delivery. We will repair or replace (at our option)
products that prove to be defective during the warranty period provided they are returned
prepaid to Jewell Instruments. No other warranty is expressed or implied. The warranty is void
if the equipment is subjected to lighting strikes, or other large potential gradients, or if it is
otherwise abused. After expiration of the warranty, Jewell will repair the equipment at its factory
for parts and labor charges. Products returned after warranty expiration should be accompanied
by a purchase order to cover repair costs. Jewell Instruments is not liable for consequential
damages.
The remedies provided herein are the buyer's sole and exclusive remedies. Jewell shall not
be liable for any direct, indirect, special, incidental, or consequential damages, whether based
on contract, tort, or any other legal theory.

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APPENDIX B - Custom Specifications for your Equipment
Signal Conditioning Unit Serial No.:____________
Transducer Wire Colors
The wire colors of the tilt and temperature transducers shipped with this unit correspond to
the following functions (see Section 2.1):
Transducer Ser. No._________
Transducer Ser. No._________
Transducer Ser. No._________
Function
Wire Color
Function
Wire Color
Function
Wire Color
+
+
+
E
E
E
-
-
-
Transducer Ser. No.________
Transducer Ser. No.________
Temperature Sensor
Function
Wire Color
Function
Wire Color
Function
Wire Color
+
+
T1
Red
E
E
T2
Orange
-
-
T3
Yellow
Filters
Your SCU has two single-pole RC low-pass filters (integrators) selected by the FILTER switch
on the front panel. The time constant (τ) for each filter setting is listed below.
After an instantaneous change in tilt, the output signal settles to 90% of this value after three
time constants, and to 98% of this value after four time constants. The corner or cutoff
frequency ƒcis defined as the frequency at which signal attenuation is 3 dB. Filter roll-off above
the corner frequency is constant at 6 dB per octave (20 dB per decade). Corner frequency can
be calculated as: ƒc= 1/(2πτ)
τvalues for filter settings:
ON: _________ seconds OFF: _________ seconds
Scale Factors
Your Signal Conditioning Unit has been calibrated for operation with the tilt transducers listed
below. However, it will operate any Jewell Instruments tilt transducer. If you purchase new tilt
transducers for use with the SCU, they should be calibrated with the SCU prior to use. Jewell
Instruments will perform these calibrations if the Signal Conditioning Unit is shipped prepaid to
our factory at the time the order for new transducers is place.

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Scale Factors are determined by moving the transducers through a range of angles and
recording the SCU output at each angle. Linear regression analysis then determines the slope
of the straight line that best fits the data. This slope is the Scale Factor. Reported below are
Scale Factors and their corresponding maximum nonlinearity.
Note: Differential Scale Factors are double single-ended Scale Factors when expressed as
volts per angular change. When Scale Factors are expressed as angular change per volt,
differential Scale Factors are one half single- ended Scale Factors.
SCU serial number: ____________
Calibration range units: ____________ Scale Factor units: ____________
"SENSOR 1" CHANNEL
Transducer
Serial No.
Calib.
Temp.
°F
Calib. Range, ±
Scale Factors
Single-
ended
Differential
High
Gain
Low
Gain
High
Gain
Max.
Nonlinearity
Low
Gain
Max.
Nonlinearity
"SENSOR 2" CHANNEL
Transducer
Serial No.
Calib.
Temp.
°F
Calib. Range, ±
Scale Factors
Single-
ended
Differential
High
Gain
Low
Gain
High
Gain
Max.
Nonlinearity
Low
Gain
Max.
Nonlinearity
Max. Nonlinearity = % of full calibration span.
The Scale Factor of the temperature output is 0.1°C/mV.

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APPENDIX C - Revision Table
REV.
PAGE NOS.
ECN NO.
DESCRIPTION OF CHANGE
DATE
B
ALL
25087
"Jewell" was "Applied Geomechanics"
Added Appendix C for revision record
2/13/13