Applied Physics Systems 751 User manual

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
APPLIED PHYSICS SYSTEMS, INC. |APPLIEDPHYSICS.COM
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MODEL 751
NATURAL GAMMA SENSOR
USER MANUAL
CONTACT US
HEADQUARTERS
425 Clyde Avenue Mountain View, CA 94043
OFFICE
650.965.0500
EMAIL
[email protected]m
APPLIEDPHYSICS.COM

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
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COPYRIGHT
Copyright 2014 - 2022 Applied Physics Systems Incorporated.
All Rights Reserved. The contents of this manual may not be reprinted in part or
whole without permission.
The contents of this manual are subject to change without notice.
TRADEMARKS
All other brands or products mentioned are trademarks or registered trademarks
of their respective holders and should be treated as such.
CONTACT INFORMATION
Applied Physics Systems
Corporate Headquarters
425 Clyde Avenue
Mountain View, California 94043 USA
Phone: [phone]
Email: [e-mail]
Web: www.appliedphysics.com
Technical Support Hours:
Monday - Friday
9:00 AM - 5:00 PM
Pacific Standard Time
DOCUMENT NUMBER
260-0222-03-0722

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
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REVISION HISTORY
Revision
Description
1
Initial Draft of this manual.
2
Removed reference to section 7.3 spreadsheet to calculate total
gamma correction factor.
3
New format
TABLE OF CONTENTS
MODEL 751.........................................................................................................................................................................1
NATURAL GAMMA SENSOR .................................................................................................................... 1
USER MANUAL..................................................................................................................................................................1
COPYRIGHT..................................................................................................................................................................... 2
TRADEMARKS................................................................................................................................................................. 2
CONTACT INFORMATION........................................................................................................................................ 2
DOCUMENT NUMBER................................................................................................................................................. 2
REVISION HISTORY...................................................................................................................................................... 3
1-INTRODUCTION......................................................................................................................................................5
2-SYSTEM SPECIFICATIONS................................................................................................................................6
3-MECHANICAL FEATURES .................................................................................................................................. 7
4-ELECTRICAL INTERFACE.............................................................................................................................................9
5-DATA INTERFACE.................................................................................................................................................10
6-MODEL 751 GAMMA SENSOR COMMANDS............................................................................................11
6.1 –MODEL 751 SYSTEM BINARY DATA REQUEST COMMANDS........................................................12
6.1.1 -ID COMMAND (KEYBOARD COMMAND 0, 0X30 HEX)...............................................................12
6.1.2 -BINARY COUNT COMMAND (KEYBOARD COMMAND 1, 0X31 HEX) ...................................13
6.1.3 -BINARY RATE COMMAND (KEYBOARD COMMAND 2, 0X32 HEX) ......................................14
6.1.4 -BINARY TRANSMISSION DECODING CONVENTION...................................................................15
6.2 –MODEL 751 SYSTEM ASCII DATA REQUEST COMMANDS...........................................................15
6.2.1 -ASCII RATE COMMAND (KEYBOARD COMMAND 6, 0X36 HEX)......................................... 16
6.2.2 -ASCII ACCELEROMETER COMMAND (KEYBOARD COMMAND 7, 0X37 HEX) ............. 16
6.2.3 -ASCII SEND 751 CONFIG DATA COMMAND (KEYBOARD COMMAND R, 0X72 HEX) 17
6.3 -MODEL 751 CONFIGURATION COMMANDS......................................................................................18
7-CORRECTIONS TO THE GAMMA COUNT RATE FOR USE IN MWD SYSTEMS ........................19

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7.1 -PRESSURE BARREL CORRECTION (PB CORRECTION)................................................................. 20
7.2 -DRILL COLLAR AND DRILLING FLUID CORRECTION (CM CORRECTION) ............................21
8-NET SYSTEMS........................................................................................................................................................23
8.1 -NET PACKET DESCRIPTION........................................................................................................................ 24
8.2 -NET PROTOCOL.............................................................................................................................................. 25
8.3 -THE CRC PROGRAM..................................................................................................................................... 26
A-MODEL 751 CONFIGURATION COMMAND REFERENCE ................................................................ 28
Tables
TABLES
Table 1. Model 751 Gamma Sensor Specifications.............................................................................6
Table 2. Model 751 Electrical Interface........................................................................................................9
Table 3. Model 751 Data Request Commands......................................................................................11
Table 4. ID Command Format Example Key.........................................................................................13
Table 5. Binary Count Command Format Example Key...............................................................13
Table 6. Rate Command Format Example Key...................................................................................14
Table 7. Model 751 Send Command Format Example Key..........................................................17
Table 8. Model 751 Operation Configuration Commands...........................................................18
Table 9. NET Packet Key..................................................................................................................................... 24
Table 10. NET Directional Sensor Command Key ............................................................................. 26
Table 11. Model 751 Configuration Commands.................................................................................. 28
FIGURES
Figure 1. Model 751 Main Connector ............................................................................................................. 7
Figure 2. Model 751 Mating Connector.......................................................................................................8
Figure 3. Model 751 Sensor Assembly Drawing.....................................................................................8
Figure 4. Model 751 Wiring Diagram.............................................................................................................9
Figure 5. Pressure Barrel Correction Factors in Inches................................................................ 20
Figure 6. Pressure Barrel Correction Factors in Centimeters ....................................................21

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1 - INTRODUCTION
The Applied Physics Systems Model 751 Gamma Sensor is designed to measure
the background gamma radiation occurring in well bores. This sensor is used
mainly to detect the presence of porous petroleum reservoirs (such as
sandstones and limestones), which are generally less radioactive than nonporous
strata (such as shales).
The Model 751 gamma sensor can be used as either a standalone system or in
conjunction with Model 750, 760, or 850 directional sensors:
• When used as a standalone system, communication with the Model 751
gamma sensor is by means of a bi-directional serial port operating at TTL
logic levels. An ASCII command language is used to send commands to
the Model 751 and data from the Model 751 is sent out in ASCII format.
• When the Model 751 is used in conjunction with a Model 750, 760, or 850
directional sensor, a NET interface is used for communication. For the NET
configuration, data from the Model 751 gamma sensor is continually
requested by the directional sensor and is combined with directional data
and transmitted out the directional sensor’s main serial data interface.
To achieve high gamma sensitivity, a 1-inch diameter by 5-inch long scintillation
crystal is used to detect gamma rays. Scintillation light flashes caused by
individual gammas are amplified by using a photo multiplier tube that outputs a
short pulse for each gamma detected. Pulses are further amplified and counted
by a microprocessor system that also handles communication with external
devices.
The Model 751 system also has two 50-gee vibration sensors (accelerometers),
which can be used to monitor drilling induced vibration and shock. The two
vibration sensors are oriented to measure axial and transverse shock and
vibration.

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
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2 - SYSTEM SPECIFICATIONS
This section describes the system specification for the Model 751 Gamma Sensor.
Table 1. Model 751 Gamma Sensor Specifications
Electrical
Input Voltage Range
+15 V to +30 V
Current Draw
90 mA @ 15 V, 45 mA @ 30 V
Power Requirements
1.5 W (max)
Logic Level
TTL
Baud Rate
User Programmable up to 9600 baud
Protocol
User selectable, ASCII or Binary
Environmental
Operating Temperature Range
0°C to 150°C
Storage Temperature Range
-25°C to +160°C
Shock
1000 G1ms half sine wave
Vibration (random)
10 Grms, 50-250Hz
Performance
Accuracy
± 5%
Thin-bed Resolution
6" (236 mm) in an 8” diameter hole
Range
0 - 511 API counts/second (30 second intervals)
Vibration and Shock Detection
2 axis ± 50 gee 400 Hz
Physical
Outside Diameter (O.D.)
1.375” (35 mm)
Length
approximately 18.3” (464.8 mm),
depending upon connector configuration
Weight
1.95 lbs (884.5 grams)
Scintillation Crystal
1" dia. (25.4 mm) and 5" (127 mm) in length,
mounted in Stainless Steel Case
Photomultiplier Tube
Hamamatsu Model 3991A
Main Connector
MDM9PH003P (ITT Cannon)
Mating Connector
MDM9SH003L (ITT Cannon)

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3 - MECHANICAL FEATURES
A drawing of the Model 751 Sensor is shown in Figure 1. When used in pulser or EM
MWD systems, usually the Model 751 is mechanically connected directly to a
Model 750, 760, or 850 directional sensor and mounted in a cylindrical pressure
barrel. An overlap mechanical connection using four 8-32 stainless steel screws is
used to attach the Model 751 to the directional sensor.
When the Model 751 is mechanically mated to the directional sensor, electrical
connection is also made via a 9-pin MDM connector mounted in the overlap
recess. This connector is float-mounted to reduce vibration-induced damage
that can occur in drilling applications.
The photographs below show the connectors in more detail:
Figure 1. Model 751 Main Connector

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The drawing below is an assembly drawing of a Model 751 gamma sensor.
Figure 3. Model 751 Sensor Assembly Drawing
Figure 2. Model 751 Mating Connector

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
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4 - Electrical Interface
The electrical connections for the Model 751 Gamma Sensor are shown in the
wiring diagram below, and in Table 2.
Table 2. Model 751 Electrical Interface
MDM Pin
Function
1
Serial (TTL level) from gamma
2
Serial (TTL level) to gamma
3
Voltage
4
Ground
Remaining pins
Not used
Communication with the Model 751 is accomplished via the TTL-level serial
communications lines. The Model 751 can be connected to a PC for testing if a
TTL-to-RS232 conversion box is inserted in the communication lines between the
Model 751 and PC. TTL-to-RS232 conversion systems can be supplied by Applied
Physics Systems or other vendors.
Figure 4. Model 751 Wiring Diagram

DOC PN:260-0222 DOC DESC: Model 751 User Manual JULY 2022. REVISION: 03
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5 - DATA INTERFACE
Commands are sent to the Model 751 as ASCII characters at the default baud rate
of 9600 using 8-bit data words with one stop bit and no parity bit.
An easy method of communicating with the Model 751 is to use a PC running a
terminal emulator program such as Windows HyperTerminal or ProComm. When
these programs are used, any typed commands are sent out the specified COM
port and any data received from the Model 751 system are displayed on the PC
display device.
When using a terminal emulator, the emulator program must be configured for
direct connect to a COM port on the PC and the following settings should be used:
• baud rate = 9600
• data word = 8-bits
• no parity
• stop bits = 1
• handshaking option = none
All commands to the Model 751 are invoked by multi byte sequences in which the
first byte is always a command token hex 06 (0x06). The bytes following the token
define the command being sent. Commands sent to the 751 system are of two
general types:
• Binary and ASCII data requests
• System configuration commands
ASCII data transmitted from the 751 sensor is formatted to be easily displayed on
a computer monitor. Binary data is transmitted from the 751 sensor in a data
packet with the following structure:
<Token> <Command> <data1> <data2>…<dataN> <CRCL> <CRCH> <token> <Eot>
Where:
• <Token> = 0x06,
• <CRCL><CRCH> is a two byte CRC, and
• <EOT> = (0x06)(0x04) and denotes the end of the packet.