WATSON INDUSTRIES ADS-C232-3AD User manual

Watson Industries, Inc. ADS-C232-3AD Rev A 10/25/2017
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Dual Axis
Vertical Reference System
Owner’s Manual
PART NUMBER: ADS-C232-3AD
WATSON INDUSTRIES, INC.
3035 MELBY STREET
EAU CLAIRE, WI 54703
Phone: [phone]
Fax: [phone]
Email: [e-mail]

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Table of Contents
Introduction................................................................................................................... 3
Product Description...................................................................................................... 3
Installation .................................................................................................................... 3
Orientation .....................................................................................................................................................................3
Mounting........................................................................................................................................................................4
Environment: .................................................................................................................................................................4
Power.............................................................................................................................................................................4
Theory of Operation ..................................................................................................... 4
Operation ...................................................................................................................... 5
Initialization...................................................................................................................................................................5
Normal Operation ..........................................................................................................................................................5
Special Operation Modes...............................................................................................................................................5
Reference Mode.........................................................................................................................................................5
Free Mode..................................................................................................................................................................5
Interface.........................................................................................................................................................................6
RS-232 Output Format...............................................................................................................................................6
RS-232 Input Commands...........................................................................................................................................7
Analog Outputs..........................................................................................................................................................9
Built in Test Digital Output .......................................................................................................................................9
Specifications.............................................................................................................. 10
Connections ................................................................................................................ 11
Dimensions ................................................................................................................. 11
WARNING................................................................................................................. 12
DISCLAIMER ............................................................................................................... 12
WARRANTY ................................................................................................................. 12
PRODUCT LIFE ............................................................................................................ 12
Appendix B................................................................................................................. 16
Activating Command Mode (Double Spacebar Mode)................................................................................................16
Accessing the Main Menu............................................................................................................................................16
Appendix B.1 Adjust Time Constants........................................................................ 16
Appendix B.2 Set Output Channels............................................................................ 16
Appendix B.3 List Output Channels .......................................................................... 17
Appendix B.4 Select Analog Attitude Full Scale Range............................................ 17
Appendix B.5 Set Baud Rate...................................................................................... 19
Appendix C................................................................................................................. 20
Watson Industries prides itself on solving customer problems and serving their needs in a timely fashion. This manual
is intended to facilitate this goal and to provide written information about your product. We ask that you carefully read
this manual. Becoming familiar with the manual will help you understand the product’s capabilities and limitations, as
well as provide you with a basic understanding of its operation. If, after reading the manual, you require further
assistance, do not hesitate to call Watson Industries with your questions and comments.

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CAUTION!
Watson Sensors are rugged devices that have been used successfully in a number of harsh
environments. The components have been qualified to withstand a mechanical shock of 500g 's or
greater, and most enclosures provide near that level of protection. However, dropping a sensor
from waist height onto a hard floor can cause a shock level of 600g's. At this level, given some
resonance, damage is possible.
Introduction
The Watson Industries Vertical Reference represents a significant advancement in inertial sensor
technology. It is a highly accurate and rugged device with many advantages over other types of
angular rate and incline-sensing devices. This manual describes operation of the Watson Industries
Vertical Reference and also provides useful application information to the system designer.
Product Description
The Watson Industries Vertical Reference System is an entirely solid-state sensor that provides
exceptional rejection from the adverse effects of inertia and short-term lateral accelerations. It does
this through the use of both an accelerometer based vertical reference and an angular rate sensor
which is integrated to provide additional information on angular position. It can be a functional
replacement for mechanical gyros which are often more expensive and which cannot provide the
reliability of a solid-state sensor. Theory of operation is described with more detail later in this
manual. The specifications, size and pinouts are also described later in this document
The Watson Vertical References provide for two types of analog output voltages. One is
proportional to angular rate and the other is proportional to angular displacement. Full-scale
analog outputs produce an output of ±5 volts dependent upon the direction of angular position or
rotation. During rotation, positive voltage output occurs in the direction of the rotational arrow
indicated in figure 2. At horizontal and zero angular rotation rate, both outputs for displacement
and rotation rate are near zero. A power supply, providing +8 to +45 Volts DC, is required to
operate the unit.
Special options in power supply, output voltage, scale calibration, and special packaging are
available as custom units. Pricing and delivery information on custom units is available by
contacting the factory.
Installation
Orientation
The base of the unit is to be mounted on top of a horizontal surface with the single foot toward the
forward direction of the vehicle. The ADS drawing, with wire call outs, is located in Figure 2. The
ADS is a rugged device and will withstand harsh environments. However, due attention needs to be
paid to the nature of the sensor and its prime function, which is to measure attitude and motion.

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Mounting
The unit has three 0.12” diameter mounting holes for using three # 4 (or 3 mm) screws. To
avoid distortion, the unit must be attached to a clean, flat surface, and the fasteners must be
tightened evenly.
Environment:
Avoid mounting sites that are subject to significant temperature variation over the duration of the
test. Temperature variation will induce significant rate sensor bias drift, which will reflect in poor
attitude accuracy.
For shipboard applications, install the sensor near the center of gravity. For all applications, it is
preferable to install the device where linear dynamic effects are minimized.
Power
This unit has an internal regulator to allow operation over a wide voltage input range. Best
operation is obtained at either +12 or +24 VDC level, although operation is fully satisfactory down
to +8 VDC and up to +45 VDC. The power ground is already connected internally to the signal
ground. Do not connect the ground wires externally. Power consumption of the unit is about
0.5W. Internal capacitors are provided to remove a reasonable level of power line noise, however,
capacitors should be added for long power line wiring or if noise is induced from other loads on the
circuit.
Theory of Operation
In order to obtain an accurate signal in both the short-term and in the long-term, the Vertical
Reference relies upon a Watson Industries angular rate sensor (ARS) combined with solid-state
accelerometers. The position output is generated by integrating the angular rate output. This signal
is compared with the output from the accelerometer and the resultant error signal is passed through
a long time constant filter and fed back as a bias to the rate sensor. The system is damped by
sending a portion of the error directly to the position integrator. By using a long time constant, the
effect of the short-term errors in the accelerometer is minimized. Thus, the adverse effects of
inertia, damping and short-term lateral accelerations on the pendulum essentially do not show up
on the vertical reference output. See Figure 1 for system overview.
Figure 1
The solid-state angular rate sensor used here works on the basic principle of detecting coriolis
forces. These forces are generated when a moving particle is rotated. To use the coriolis effect to
detect angular rotation, a solid structure is forced to vibrate normally at its resonant frequency. The
vibration provides the structure with a linear velocity component. When the structure is rotated, the
coriolis forces cause the vibration motion of the structure to be coupled to another vibration mode

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or plane of the structure. The magnitude of this secondary vibration is proportional to the angular
rate of turn.
Operation
Initialization
Ideally, the ADS should be stationary when it is turned on. If not, the sensor readings may not be
accurate after initialization. The time required for the initialization process is not the same for
every type of ADS, but typically takes 4 to 5 seconds. During this time, a message is sent from the
unit via the RS-232 serial link. This message gives information about the ADS such as the full
model number, serial number, and software revision. The message can be read by using a terminal
program or by using the terminal mode of Watson Industries’ communication software.
The ADS can also be “re-initialized” after it has been turned on. This is especially useful if the
sensor has been used in severe maneuvers that have over ranged the angular rate sensors and
caused significant errors to accumulate. Sometimes re-initializing the unit will allow for a faster
recovery than waiting for the error correction routines to correct the sensor readings. There are
several ways to re-initialize the ADS. For more information, see the Interface section of this
manual.
Normal Operation
In normal operation, the ADS takes data from its internal rate sensors and integrates them in a
closed loop system, with the accelerometers as a long-term reference, to generate the Bank, and
Elevation data. In most cases, these algorithms provide for very stable and accurate output signals;
however, the user should be aware that exceeding the normal ranges of the sensors would affect
accuracy. For example, while custom ADS units may have differing ranges, the rate gyros in a
typical ADS have a maximum rate of 100°/s. Care should be taken not to exceed this rate because
the closed loop system will receive inaccurate rate data. This will result in errors in the angle output
signals.
Special Operation Modes
Reference Mode
This mode is usually used for calibration or diagnostics. When in reference mode, the ADS will
output data generated directly from the sensor reference signals rather than as a product of the
closed loop integration used for normal operation. The reference command provides the same
sensor information as in normal operation mode with the following differences:
Bank and Elevation are obtained directly from the accelerometers - no gyro stabilization.
Angular Rate Sensors are not close-loop bias corrected, and the X and Y angular rate data
channels output X and Y Rate Bias values
The reference mode can be selected through the terminal mode. Note that reference mode is never
a default setting. It must be re-selected when re-powering the unit.
Free Mode
While in Free Mode, the ADS will output data from the sensors without correction by the
references. For example, the Bank Angle data output in Free Mode is calculated directly from the
X-axis Rate Sensor. In this case, the angle is a direct integration of the roll rate. Free Mode can be
used to totally reject effects from dynamic accelerations, but accuracy degrades with time. It is

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intended for use over periods of a few minutes at a time. This mode provides similar sensor
information as in normal operation mode with the following differences:
Bank and Elevation are obtained directly from the rate gyros.
Angular Rate Sensors are not close-loop bias corrected.
Free mode can be accessed through command mode (See Appendix B). Note that free mode is
never a default setting. It must be re-selected when re-powering the unit. The user should not enter
free mode until after the ADS is initialized and its readings are stable.
Interface
RS-232 Output Format
The standard RS-232 output is received from the 12-pin connector. The digital output pin map can
be found in the Connections section of this manual. The RS-232 output consists of a string of
decimal ASCII characters sent asynchronously at regular intervals. By default, the string is sent at
9600 baud with eight data bits, one stop bit and no parity. The RS-232 signal is referenced to signal
ground. The number of strings sent per second depends on the baud rate and the output format. The
maximum rate is 250 strings per second. The contents of a typical string are formed as follows:
(See Appendix B for information on how to change the data string.)
1. A single letter and a space used to indicate the start of the data string. The letter “I”
indicates the start of an inertial data string. The letter “R” indicates the start of a Reference
data string. If the letter is in lower case (“i” or “r”), an error over-range condition is
indicated (see below).
2. A seven character string representing the bank angle starting with a space, then a “+” or a
“-“, followed by three digits, a decimal point and one digit and for up to ±179.9 degrees.
3. A six character string representing the elevation angle starting with a space, then a “+” or a
“-“, followed by two digits, a decimal point and one digit for up to ±89.9 degrees.
4. A six character string representing the X axis angular rate starting with a space, then a “+”
or a “-“, followed by two digits, a decimal point and one digit for up to ±99.9 °/second.
5. A five character string representing the Y axis angular rate starting with a space, then a “+”
or a “-“, followed by two digits, a decimal point and one digit for up to ±99.9 °/second.
6. The string is terminated by a carriage return. There will then be a short interval with no
data transmission before the next string begins.
Example:
I +002.5 -05.0 +00.9 -00.4 <CR>
(1)
bank
angle
(2)
elev.
angle
(3)
X axis
Rate
(4)
Y axis
rate
(5) (6)
space space space space

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The string transmission rate can be improved by reducing the amount of information (data items)
transmitted. The data items transmitted can be changed by using special commands to modify the
EEPROM of the unit (see Appendix B). More channels are available for output (see Appendix A).
The system is protected from inadvertent write-over of the EEPROM by requiring two spacebar
commands during the initialization interval to access the EEPROM or related functions.
The baud rate may be changed from the nominal value of 9600 baud by modifying the default
value in the EEPROM of the unit to 38.4K, 19.2K, or 4800 baud.
A text header that is sent by the ADS during initialization identifies the unit by part number and by
serial number and gives the date of last calibration. Additionally, a line of text characters that
identifies the data channel columns is sent if the serial output is set to ASCII decimal. This whole
message can be temporarily (or as a default) suppressed or restored by a “*” command from the
interfacing computer.
Data transmission sent by the ADS can also be suppressed or restored by a “+” command from the
interfacing computer. This command is typically used when only analog data is used as a noise
reduction measure.
The error over range condition is indicated by the use of a lower case “i” or “r” when the calculated
attitude error exceeds the ranges listed above. Internal functions that require these error values are
disabled while the condition exists. The system will continue to operate in an extended time
constant mode with a low level of error accumulation until the condition is cleared. Occasional
blips of this condition are expected with no detectable affect on the resulting data.
The other output format available is a binary format. The binary format provides generally the
same information as the decimal ASCII format, but in a compact binary file message. In this
format, there are nominally 9 bytes sent that represent 4 fourteen-bit output channels followed by a
carriage return. Again, this may be reduced to improve the update rate by using special commands
to modify the EEPROM of the unit. This format is for highly experienced users only. See
Appendix C for more information. Consult the factory for further details.
RS-232 Input Commands
The RS-232 input commands are provided for the purpose of unit test and installation set-up. Use
the same parameters that are used for the output (9600 baud ASCII nominal, or as reset in the units
EEPROM).
Note: Many commands require command or “Double spacebar mode” in order to access them. For
more information on how to activate Command Mode, see the instructions in Appendix B.
These commands are available to the user (others are used at the factory for alignment and
calibration):
1. An “R” or “r” will set the outputs (analog and serial) to their Reference Command modes.
This mode is used in installation to physically align the unit. Command mode is required
for access to this command.
2. An “I” or “i” sets the unit to Inertial mode. Switching to this mode clears the Reference
Command mode. This is the default mode at power up and is the normal operating mode.
Command mode is required for access to this command.

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3. An “F” or “f” will disconnect the references from the attitude system and is the Free Mode
Command. Free mode is used to make the system ignore the references during high
maneuvers and brief disturbances. This mode is not intended for use except in brief
intervals, since errors will grow geometrically. Command mode is not required to access
this function.
4. A “K” or “k” will clear the Free Mode Command. Command mode is not required to access
this function.
5. An “!” will reinitialize the unit. Further, access to initialization is inhibited such that a
spacebar command must be sent within about 2 seconds of the “!” command for
initialization to be engaged. Command mode is not required to access this function.
6. A “Z” or “z” will reset the timer channel counter. The timer channel counts seconds since
the last reset. This command sets the timer back to zero. Command mode is not required to
access this function.
7. A “L” or “l” will transmit a line of labels corresponding to the data channels that are
currently selected for output. See Appendix A for information about the data channels and
their labels. Command mode is required for access to this command.
8. An “_” command will change the output format to decimal ASCII. This change is made
non-volatile in the unit on EEPROM by keying in the quote (“) character. Command mode
is required for access to this command.
9. A “^” command will change the output format to binary. This change is made non-volatile
in the unit on EEPROM by keying in the quote (“) character. Command mode is required
for access to this command.
10. A “:” command will toggle the output to send a frame of data upon receiving any non-
command character (On to Off; Off to On). This change is made non-volatile in the unit on
EEPROM by keying in the quote (“) character. Command mode is required for access to
this command.
Note: To test if this command is active when the unit is not flowing data, send a carriage
return (or any other non-command character to the sensor, and observe if there is any
output.
11. A “+” command will suppress or restore the transmission of data. This command will
toggle the data transmission (On to Off; Off to On). Command mode is required for access
to this command.
Note: It is possible for both the “:” and the “+” commands to be active at the same time.
The “+” command determines whether the sensor is allowed to transmit data. So if this were
the case, the “:” command must also be turned off to allow the free flow of data.
12. An “*” command will suppress or restore the initialization message in the Decimal ASCII
mode. This command will toggle the transmitting of the text header during initialization
(On to Off; Off to On). This change is made non-volatile in the unit on EEPROM by keying
in the quote (“) character. Command mode is required for access to this command.

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13. An “&” command brings up a menu which allows any of several parameters to be set.
These are system time constants, selection of data channels for serial output, and baud rates.
This change is made non-volatile in the unit on EEPROM by keying in the quote (“)
character. Command mode is required for access to this command.
The commands “~”, “@”, “#”, “$”, ‘(“, “)”, “{“, “}”, “|”, “<”, “>” and “?” are used by the Watson
factory to calibrate the unit and should be used only with the assistance of the factory. If an
undesired function is called, a “Q”, and sometimes Escape or a Delete will interrupt the command
and return to operation with the least disturbance to the system. All other unspecified characters
such as carriage return, line feed and space are ignored by the system.
If there are problems with the system “hanging up” during the binary output mode, check for
crosstalk between the serial transmit and receive line in your installation. In addition, check to see
that the communications program used is not sending an echo. This will not happen in the decimal
or hexadecimal modes because command characters recognized by the system are not produced in
those modes.
Analog Outputs
Analog signals are output from a 14 bit digital to analog converter through an operational amplifier.
Each analog output has a 300 ohm resistor in series to eliminate oscillations from high capacitance
loads. The output range for all of the analog output channels is ±5 Volts with respect to the
common signal ground. The analog outputs can be found on the 12-pin connector. The outputs
include:
Signal Pin Range Output Range 0 VDC Scale Factor
Bank (X Angle) 9 ±30°* ±5V 0° 6.0°/V *
Elevation (Y angle) 3 ±30°* ±5V 0° 6.0°/V *
Roll Rate (X Axis) 10 ±100°/s ±5V 0°/s 20°/s/V
Pitch Rate (Y Axis) 2 ±100°/s ±5V 0°/s 20°/s/V
* The Analog output range for Bank & Elevation is menu selectable. This also changes the analog scale
factor for Bank & Elevation.
The output range for both Bank and Elevation are menu selectable.
Available Ranges Output Range 0 VDC Scale Factor
±30°±5V 0° 6.0°/V
±45°±5V 0° 9.0°/V
±60°±5V 0° 12°/V
±90°±5V 0° 18°/V
±180°* ±5V 0° 36°/V
*Maximum Elevation range is ±90°
See Appendix B for more information on selecting Bank and Elevation ranges.
Built in Test Digital Output
Built-In Test is an active low digital output that continuously monitors the internal sensors for
faults. This signal is available on pin 5 of the connector. This output is High (3.3VDC) when the
unit is operating normally. This output is Low (ground) when a fault is indicated. The BIT Test
Flag of the Flag channel gives a similar indication. Flag reset is normal operation; Flag Set is a
fault condition. The BIT status byte that is available as part of the output message will give more
information on the fault conditions.

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Specifications
Attitude
Range: Bank ±180° (±30° †) Digital (Analog)
Range: Elevation ±90° (±30° †) Digital (Analog)
Resolution: 0.02° Binary mode (14 bit)
Analog Scale Factor: 6°/V † ±5V Output
Accuracy: Static ±0.5° (up to 75°)
* Accuracy: Dynamic
0.5%
Angular Rate
Range: Roll, Pitch ±100°/sec
Resolution: 0.025°/sec Binary mode (14 bit)
Analog Scale Factor: 20°/sec/V ±5V Output
Scale Factor Accuracy: 0.5%
Bias: Roll, Pitch < 0.3°/sec ±0.02°/sec Binary mode (14
bit)
Non-Linearity: < 0.2% Full scale range
Bandwidth: 50 Hz
Noise: < 0.06°/sec rms
Acceleration
Range: X, Y, Z ±10g
Resolution: 4mg
Scale Factor Accuracy: 1%
Bias: X, Y, Z < 10mg
Non-Linearity: 0.1% Full scale range
Bandwidth: 3 Hz
Environmental
Temperature: Operating -40°C to +85°C
Temperature: Storage -55°C to +85°C
Vibration: Operating 5g rms 20 Hz to 2 KHz
Vibration: Survival 10g rms 20 Hz to 2 KHz
Shock: Survival 500g 1mS ½ sine wave
Electrical
Frame Rate: 250 Hz Maximum
Startup Time: Data 5 sec
Startup Time: Fully operational 10 sec
Input Power: 8 to 45VDC 0.5W
Input Current: 40mA @ 12VDC 20mA @ 24VDC
Digital Output: RS-232
Analog Output: ±5VDC
Analog Output Impedance: 300 Ohm Per line
Physical
Axis Alignment: < 0.25°
Size: Including Mounting Flanges
1.2"W x 2.8"L x 1.35"H 3.0 x 7.1 x 3.4 (cm)
Weight:
2.1 oz 60 grams
Connection: Amp 4-794627-2 (12 pin)
*
Actual accuracy can be calculated as the listed percentage multiplied by the change in value over the entire dynamic maneuver.
†
The Analog output range for Bank & Elevation is menu selectable. This also changes the analog scale factor for Bank &
Elevation.
Specifications are subject to change without notice.
This product may be subject to export restrictions. Export Classification ECCN 7A994.

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Connections
123456
789101112
The RS-232 serial and analog output connections are referenced to Signal Ground on pin 8. The
power ground is already connected internally to the signal ground.
Dimensions
X
Y
X
ZZ
Y
X Y
WATSONINDUSTRIES,INC.
www.watson-gyro.com
MADEINU.S.A
P/NRev
Pwr.
S/F
Figure 2
12 Pin Connector
Pin Description
1 RS-232 TXD
2 Y Angular Rate Analog Output
3 Elevation (Y) Angle Analog Output
4 No Connection
5 Built in Test (BIT) Output
6 Power Ground
7 RS-232 RXD
8 Signal Ground
9 X Angular Rate Analog Output
10 Bank (X) Angle Analog Output
11 Factory use (Do not Connect)
12 +Vin Power +8 to +45 VDC)

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WARNING
Rough handling or dropping of this unit is likely to cause damage.
Over-voltage and/or miswiring of this unit will cause damage.
This unit should be protected against prolonged exposure to high
humidity and/or salt air environments.
DISCLAIMER
The information contained in this manual is believed to be accurate and reliable; however, it is the
user’s responsibility to test and to determine whether a Watson Industries’ product is suitable for a
particular use.
Suggestion of uses should not be taken as inducements to infringe upon any patents.
WARRANTY
Watson Industries, Inc. warrants, to the original purchaser, this product to be free from defective
material or workmanship for a period of one full year from the date of purchase. Watson
Industries’ liability under this warranty is limited to repairing or replacing, at Watson Industries’
sole discretion, the defective product when returned to the factory, shipping charges prepaid, within
one full year from the date of purchase. The warranty described in this paragraph shall be in lieu of
any other warranty, express or implied, including but not limited to any implied warranty of
merchantability or fitness for a particular purpose.
Excluded from any warranty given by Watson Industries are products that have been subject to
abuse, misuse, damage or accident; that have been connected, installed or adjusted contrary to the
instructions furnished by seller; or that have been repaired by persons not authorized by Watson
Industries.
Watson Industries reserves the right to discontinue models, to change specifications, price or
design of this product at any time without notice and without incurring any obligation whatsoever.
The purchaser agrees to assume all liabilities for any damages and/or bodily injury that may result
from the use, or misuse, of this product by the purchaser, his employees or agents. The purchaser
further agrees that seller shall not be liable in any way for consequential damages resulting from
the use of this product.
No agent or representative of Watson Industries is authorized to assume, and Watson Industries
will not be bound by any other obligation or representation made in connection with the sale and/or
purchase of this product.
PRODUCT LIFE
The maximum expected life of this product is 20 years from the date of purchase. Watson
Industries, Inc. recommends the replacement of any product that has exceeded the product life
expectation.

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Customer Service
All repairs, calibrations and upgrades are performed at the factory. Before returning any product,
please contact Watson Industries to obtain a Returned Material Authorization number (RMA).
Return Address & Contact Information
Watson Industries, Inc.
3035 Melby Street
Eau Claire, WI 54703
ATTN: Service Department
Telephone: [phone] Fax: [phone] email: [e-mail]
Returning the Product
Product shall be packaged making sure there is adequate packing around all sides. Correspondence shall
include:
• Customer’s Name and Address
• Contact Information
• Equipment Model Number
• Equipment Serial Number
• Description of Fault
It is the customer’s responsibility to pay all shipping charges from customer to Watson
Industries, including import and transportation charges.

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Appendix A
The following outputs are available via the RS-232 serial link. Their full-scale ranges are listed for both decimal and
binary format.
Inertial Output Label Full Scale Decimal Full Scale Binary
Time Since Reset TM 65535 16383
Bank BK ±179.9º ±180º
Elevation EL ±89.9º ±180º
X Acceleration XA ±9.99 g ±10 g
Y Acceleration YA ±9.99 g ±10 g
Z Acceleration ZA ±9.99 g ±10 g
X Angular Rate XR ±99.9 º/s ±200 º/s
Y Angular Rate YR ±99.9 º/s ±200 º/s
Bank Pendulum (simulated)
XI ±179.9º ±180º
Elevation Pendulum (simulated) YI ±89.9º ±180º
Temperature TP -40º to 88ºC -40º to 88ºC (7 bit)
Flag Bits FL 3 ASCII chars representing Octal
digits 1 byte
Status Bits ST 3 ASCII chars representing Octal
digits 1 byte
Built In Test (BIT) Status Bits BT 3 ASCII chars representing Octal
digits 1 byte
The Flag Bits contain the following information:
Bit Description (If Set)
0 Bank Error Flag
1 Elevation Error Flag
2 Unit Temp Out of Range Flag
3 BIT Test Flag
4 X Rate Out of Range Flag
5 Y Rate Out of Range Flag
6 Checksum Error Flag
7 Unused
Example: The Flag channel output in ASCII Decimal is “042”
Octal Digit 0 4 2
Binary Equivalent 0 0 1 0 0 0 1 0
Flag Bit # 7 6 5 4 3 2 1 0
This translates into the information below:
Bit 7 Reset
Bit 6 Reset No Checksum Error
Bit 5 Set X Rate Out Range (>140 º/s)
Bit 4 Reset Y Rate in Range
Bit 3 Reset No BIT Error
Bit 2 Reset Unit Temp in Range (-40º to +85º C)
Bit 1 Set Elevation Error
Bit 0 Reset No Bank Error

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The Status Bits contain the following information:
Bit Description
0 to 2 Show the current system time constant, using the following equation:
TC=2(Flag Value + 1)
3 If set, Reference Command selected
4 If set, Unit is in Initialization
5 If set, Free Mode selected
6 If set, Command Mode is Selected
7 Unused
Example: The Status channel output in ASCII Decimal is “112
Octal Digit 1 1 2
Binary Equivalent 0 1 0 0 1 0 1 0
Status Bit # 7 6 5 4 3 2 1 0
This translates into the information below:
Bit 7 Reset
Bit 6 Set Command mode active
Bit 5 Set Not in Reference mode
Bit 4 Reset Not in Initialization
Bit 3 Set Free mode active
Bit 2
Bit 1
Bit 0
2
The Current System Time Constant = 2
(Flag Value+1)
=2
(2+1)
= 2
(3)
= 8 seconds
The Built In Test (BIT) Status Bits contain the following information:
Bit Description
0 If set, X Accelerometer Sensor Failure
1 If set, Y Accelerometer Sensor Failure
2 If set, Z Accelerometer Sensor Failure
3 If set, Sensor Temperature out of range
4 If set, X Angular Rate Sensor Failure
5 If set, X Angular Rate Sensor Failure
6 Unused
7 Unused
Example: The BIT Test channel output in ASCII Decimal is “042”
Octal Digit 0 4 2
Binary Equivalent 0 0 1 0 0 0 1 0
BIT Status Bit # 7 6 5 4 3 2 1 0
This translates into the information below:
Bit 7 Reset
Bit 6 Reset
Bit 5 Set X Rate Sensor Failure
Bit 4 Reset No Y Rate Sensor Failure
Bit 3 Reset Temp Sensor in range
Bit 2 Reset No Z Accelerometer Failure
Bit 1 Set Y Accelerometer Failure
Bit 0 Reset No X Accelerometer Failure

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TYPE IN THE NUMBER OF YOUR SELECTION (OR 'Q' TO QUIT):
1 = ADJUST TIME CONSTANTS
2 = SET OUTPUT CHANNELS
3 = LIST CURRENT OUTPUT CHANNEL SELECTION
4 = SELECT ANALOG ATTITUDE FULL SCALE RANGE
5 = SET NEW BAUD RATE
Appendix B
Activating Command Mode (Double Spacebar Mode)
1) Connect the unit to a DC power source that is off.
2) The viewing computer needs a valid bi-directional RS-232 serial port. Connect the serial
port of the Watson sensor to the computer’s serial port.
3) Open a terminal program (such as HyperTerminal) to interface with the unit. The default
baud rate of the unit is 9600 baud. Make sure the computer’s serial port is open.
4) Power-on the unit. A startup message will be transmitted by the unit and will appear in the
terminal window unless it has been suppressed (See RS-232 Input Commands above).
5) During initialization, hit the space bar twice within close succession.
Note: The sensor initialization time begins after the startup message is transmitted.
Typically, this time period lasts 5 seconds, but could be as long as 127 seconds depending
on your sensor.
6) Wait until after initialization is finished. At this point, command mode will be activated and
the unit will accept keyboard commands.
Note: Most Watson sensors have initialization times that are shorter than 30 seconds. Any
extra keystrokes (other than two spacebars) sent during initialization will deactivate
command mode.
**It can often take a few attempts to get the hang of step 5. Repeat steps 4-6 until successful.
Accessing the Main Menu
1) Activate Command Mode (See above)
2) Typing ‘&’ will bring up the main menu:
Appendix B.1 Adjust Time Constants
1) To adjust the system time constants, type ‘1’ at the main menu.
These settings can dramatically change the operation of the sensor and we recommend that any
changes be made with the direction of Watson Industries engineering.
Appendix B.2 Set Output Channels
1) To change the output channels, type ‘2’ at the main menu.

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This will bring up the following message:
2) To proceed type 'Y'. Stop this process by typing either ‘N’ or ‘Q’.
If ‘Y’ is pressed, each channel will come up one at a time.
For example:
3) Type 'Y' to output the channel, type 'N' to remove the channel.
After the last channel is listed, this message will appear:
4) To accept the new channels type 'N'. Typing a ‘Y’ with start the command sequence over.
Typing a ‘Q’ at any time in the sequence will quit without updating the channels.
Changes made will not change the non-volatile settings. To make these new settings the default
value, send a Quotation Mark (“).
5) Press the space bar after quitting or updating the new channels to restart the data flow.
Appendix B.3 List Output Channels
1) To list the current output channel selection, type ‘3’ at the main menu.
2) The sensor will show which channels are currently active.
Appendix B.4 Select Analog Attitude Full Scale Range
1) To update the scale factor for the analog Bank output, type ‘4’ at the main menu.
This will bring up the menu:
2) To change the Bank Angle setting. type ‘1’ at this menu.
This will bring up the menu:
TO SET FOR OUTPUT FOR ANY OF THE FOLLOWING DATA ITEMS, PRESS Y
TO AVOID ANY OF THE FOLLOWING DATA ITEMS, PRESS N
TO QUIT AND DISREGARD ANY OTHER DATA, PRESS Q
*** DO YOU WANT TO PROCEED? (Y/N/Q)
DO YOU WANT OUTPUT TIME SINCE RESET?
Y = GOBACK, N = INSTALL DATA & QUIT, Q = QUIT
DO YOU WANT TO TRY TO SET DATA AGAIN?
SELECT ATTITUDE FOR SCALE FACTOR UPDATE (OR 'Q' TO QUIT):
1 = ANALOG BANK ANGLE
2 = ANALOG ELEVATION ANGLE

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3) Change the Analog Bank Range to a new setting.
To change the Bank Angle to Scale Factor 6.0°/V , type ‘1’.
To change the Bank Angle to Scale Factor 9.0°/V , type ‘2’.
To change the Bank Angle to Scale Factor 12°/V , type ‘3’.
To change the Bank Angle to Scale Factor 18°/V , type ‘4’.
To change the Bank Angle to Scale Factor 36°/V , type ‘5’.
4) To update the scale factor for the analog Elevation output, type ‘4’ at the main menu.
This will bring up the menu:
5) To change the Elevation Angle setting. type ‘2’ at this menu.
This will bring up the menu:
6) Change the Analog Elevation Range to a new setting.
To change the Elevation Angle to Scale Factor 6.0°/V , type ‘1’.
To change the Elevation Angle to Scale Factor 9.0°/V , type ‘2’.
To change the Elevation Angle to Scale Factor 12°/V , type ‘3’.
To change the Elevation Angle to Scale Factor 18°/V , type ‘4’.
To change the Elevation Angle to Scale Factor 36°/V , type ‘5’.
THE CURRENT SETTING IN DEG/V IS: 6.0
TYPE IN THE NUMBER OF YOUR SELECTION (OR 'Q' TO QUIT):
1 = BANK ANGLE SCALE FACTOR 6.0 DEG/V
2 = BANK ANGLE SCALE FACTOR 9.0 DEG/V
3 = BANK ANGLE SCALE FACTOR 12 DEG/V
4 = BANK ANGLE SCALE FACTOR 18 DEG/V
5 = BANK ANGLE SCALE FACTOR 36 DEG/V
SELECT ATTITUDE FOR SCALE FACTOR UPDATE (OR 'Q' TO QUIT):
1 = ANALOG BANK ANGLE
2 = ANALOG ELEVATION ANGLE
THE CURRENT SETTING IN DEG/V IS: 6.0
TYPE IN THE NUMBER OF YOUR SELECTION (OR 'Q' TO QUIT):
1 = ELEVATION ANGLE SCALE FACTOR 6.0 DEG/V
2 = ELEVATION ANGLE SCALE FACTOR 9.0 DEG/V
3 = ELEVATION ANGLE SCALE FACTOR 12 DEG/V
4 = ELEVATION ANGLE SCALE FACTOR 18 DEG/V
5 = ELEVATION ANGLE SCALE FACTOR 36 DEG/V

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Appendix B.5 Set Baud Rate
1) To change the baud rate at which the sensor communicates, type ‘4’ at the main menu.
This will bring up the menu:
7) Change the baud rate to a new setting.
To change to 38,400 Baud, type ‘1’.
To change to 19,200 Baud, type ‘2’.
To change to 9,600 Baud, type ‘3’.
To change to 4,800 Baud, type ‘4’.
The baud rate change will take effect immediately. To make the new baud rate the default
setting, send a quote symbol (“) using the new baud rate. Otherwise the old baud rate will
return the next time the unit is powered up.
Note: The baud rate of the software that is communicating to the sensor will need to be changed
to match the new setting.
8) Press the space bar to resume data transmission.
The factory settings for serial communications are 9.6K baud with 8 bits and one stop bit, no parity.
TYPE IN THE NUMBER OF YOUR SELECTION (OR 'Q' TO QUIT):
( EFFECTIVE IMMEDIATELY - SAVE TO MAKE PERMANENT)
1 = 38.4 K BAUD
2 = 19.2 K BAUD
3 = 9.6 K BAUD
4 = 4.8 K BAUD

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Appendix C Binary Data Format
All of the data words have a high sign bit, but the delimiter byte is an ASCII carriage return character that has a low
sign bit. One word per output parameter.
Example: Unit is sending out Bank, Elevation, X Angular Rate, & Y Angular Rate
The Unit is seeing these conditions:
Binary Output Format:
The Carriage return byte is the only byte which has a value less than 128 (0x80). This is the Synchronizing Byte.
76543210 76543210
Data Word
MSB LSB
Bit 7 of the MSB is set to 1. Bits 6 to 0 of the MSB are the upper 7 bits of the data. (sign plus 6 bits of data)
Bit 7 of the LSB is set to 1. Bits 6 to 0 of the LSB are the lower 7 bits of the data.
As the data words are received, the LSB is shifted left to shift out the 7th bit (always set to 1). The MSB is then
connected to the LSB as a 16-bit word. This word is then shifted left to shift out the 7th bit (always set to 1). What
remains is a signed fractional word with a resolution of 13 bits plus a sign bit.
To convert binary data:
Split each word into two bytes:
Remove the most significant bit from each byte:
Bank Elevation X Rate Y Rate
15.0˚ -5.0˚ 10.2˚/s -3.1˚/s
Word1 Word2 Word3 Word4 <CR> byte
0x85AA 0xFE9C 0x83A1 0xFF81 0x0D
Bank Elevation X Rate Y Rate
0x85AA 0xFE9C 0x83A1 0xFF81
Bank Elevation X Rate Y Rate
0x85
0xAA 0xFE 0x9C 0x83 0xA1 0xFF 0x81
Bank Elevation X Rate Y Rate
0x05
0x2A 0x7E 0x1C 0x03 0x21 0x7F 0x01