Applied Physics Systems 1540 User manual

MODEL 1540
FLUXGATE MAGNETOMETER
USER MANUAL
CONTACT US
HEADQUARTERS
425 Clyde Avenue Mountain View, CA 94043
OFFICE
650.965.0500
EMAIL
[email protected]m
APPLIEDPHYSICS.COM

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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: [email protected]
Web: www.appliedphysics.com
Technical Support Hours:
Monday - Friday
9:00 AM - 5:00 PM
Pacific Standard Time
DOCUMENT NUMBER
260-0183-03-0722

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REVISION HISTORY
Revision
Description
Date
1
Initial draft of this manual.
June 2014
2
Renamed “binary constant” to “byte constant”.
April 2017
Renamed “floating constant” to “float constant”.
Updated system specifications.
Table 1. System Specifications
Updated the Model 1540 mechanical drawing.
Figure 1. Model 1540 Cylindrical Magnetometer
Updated the Model 1540S mechanical drawing.
Figure 2. Model 1540S Rectangular
Magnetometer Mechanical Drawing
Updated the Model 1540 and 1540S electrical
interface.
Table 3. Model 1540S Electrical Interface,
Figure 2. Model 1540S Rectangular
Magnetometer Mechanical Drawing and Figure
3. Model 1540 with Leads
Updated the Model 1540 sensor commands.
Table 4. Model 1540 Commands
Updated the byte constants.
Table 5. Commonly Used Byte Constants and
Table 12. Model Byte Constants
Updated the float constants.
Table 13. Model 1540 Float Constants
3
New Format
July 2022

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TABLE OF CONTENTS
MODEL 1540 ........................................................................................................................................................................................ 1
COPYRIGHT ........................................................................................................................................................................................ 2
TRADEMARKS ....................................................................................................................................................................................2
CONTACT INFORMATION ...........................................................................................................................................................2
DOCUMENT NUMBER .................................................................................................................................................................... 2
REVISION HISTORY..........................................................................................................................................................................3
FIGURES................................................................................................................................................................................................5
TABLES...................................................................................................................................................................................................5
1–INTRODUCTION.........................................................................................................................................................................6
2-SYSTEM SPECIFICATIONS.................................................................................................................................................... 7
3-MECHANICAL FEATURES ......................................................................................................................................................9
4-ELECTRICAL INTERFACE........................................................................................................................................................11
4.1 -SETTING UP THE ELECTRICAL CONNECTIONS...................................................................................................... 14
5-COMPUTER INTERFACE....................................................................................................................................................... 16
5.1 –MODEL 1540 SENSOR COMMANDS .......................................................................................................................... 16
5.2 -1540 BYTE CONSTANTS.................................................................................................................................................. 19
5.3 –MODEL 1540 FLOAT CONSTANTS ............................................................................................................................ 20
5.4 -ASCII AND BINARY MODE ............................................................................................................................................. 20
5.5 -CONFIGURING THE MODEL 1540 SYSTEM............................................................................................................ 22
5.5.1 -CHANGING THE ASCII DATA OUTPUT MODE................................................................................................... 23
5.5.2 -CHANGING THE BAUD RATE.................................................................................................................................... 23
5.5.3 -CONFIGURING THE MODEL 1540 SENSOR FOR AUTOSEND.................................................................... 24
5.5.4 -AVERAGING AND FILTERING MODEL 1540 OUTPUT DATA.......................................................................25
5.6 -USING THE ASCII COMMUNICATION MODE....................................................................................................... 26
5.6.1 -ASCII AUTOSEND MODE ..............................................................................................................................................27
5.7 -STANDARD BINARY COMMUNICATION MODES................................................................................................27
5.7.1 -COMMAND <128>: SEND SENSOR (VECTOR) DATA IN STANDARD BINARY FORMAT................ 28
5.7.2 -COMMAND <129>: SEND ALL DATA AS VECTORS IN AN IEEE FLOAT FORMAT............................... 29
5.7.3 -AUTOSEND BINARY COMMUNICATION MODE..............................................................................................30
6-OPERATING THE MODEL 1540......................................................................................................................................... 30
6.1 -SENSOR INTERFACE SOFTWARE...................................................................................................................................31
A-BYTE CONSTANTS AND FLOAT CONSTANTS......................................................................................................... 38
A.1 –MODEL 1540 BYTE CONSTANTS.................................................................................................................................38
A.2 –MODEL 1540 FLOAT CONSTANTS ............................................................................................................................ 42

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FIGURES
Figure 1. Model 1540 Cylindrical Magnetometer..................................................................................9
Figure 2. Model 1540S Rectangular Magnetometer Mechanical Drawing.......................10
Figure 3. Model 1540 with Leads......................................................................................................................11
Figure 4. Averaging Example......................................................................................................................... 26
Figure 5. Model 1540 Noise Level Data.......................................................................................................31
Figure 6. Sensor Interfacce Main Display.............................................................................................. 33
Figure 7. Sensor Configure Window.......................................................................................................... 34
Figure 8. Monitor Sensor Window ............................................................................................................... 36
Figure 9. Monitor Sensor Window - ASCII Mode................................................................................ 36
Figure 10. Monitor Sensor Window - Hex Mode...................................................................................37
TABLES
Table 1. System Specifications......................................................................................................................... 7
Table 2. Model 1540 Electrical Interface...................................................................................................12
Table 3. Model 1540S Electrical Interface ................................................................................................13
Table 4. Model 1540 Commands ..................................................................................................................17
Table 5. Commonly Used Byte Constants..............................................................................................19
Table 6. Changing the ASCII Data Output Mode..............................................................................23
Table 7. Baud Rate Settings............................................................................................................................ 24
Table 8. Autosend Modes................................................................................................................................. 25
Table 9. Averaging Values............................................................................................................................... 25
Table 10. Command <80 Hex, 128> Data Format Key.................................................................... 28
Table 11. Command <129> Data Format Key........................................................................................ 29
Table 12. Model Byte Constants ................................................................................................................... 38
Table 13. Model 1540 Float Constants ...................................................................................................... 42

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1 – INTRODUCTION
The Applied Physics Systems Model 1540 is a high speed 3-axis fluxgate
magnetometer employing 22-bit analog-to-digital converters. Magnetic field
data transmitted by the Model 1540 is expressed in Gauss (G).
The Model 1540 system employs three ring core fluxgate sensors together with
analog processing electronics to produce analog output voltages proportional to
the measured magnetic field along three orthogonal axes. The analog output
voltages are converted to digital form using three 24-bit A/D converters. Using 22-
bit converters enables the 1540 system to measure magnetic field magnitudes
from ±0.65 G down to the system noise level (5 microG peak to peak) using a
single range.
The Model 1540 system microprocessor (MSP430) performs the following digital
control functions:
• control and acquisition of data from the 22-bit A/D converter
• correction of fluxgate sensor scale, offset, and alignment factors
• implementation of serial communications between the system and an
external computer
The Model 1540 is calibrated by placing it in a precision 3-axis Helmholtz coil,
which enables the application of accurately known magnetic fields to the system.
Then the Helmholtz coil is fitted with a holding fixture with alignment holes and
reference V grooves that match the 1540 alignment pins and cylindrical body. The
holding fixture enables the Model 1540 to be accurately aligned with the Helmholtz
axes, so that accurate scale and alignment and offset factors can be determined.
After determining the calibration factors, they are downloaded into the 1540 so
the system microprocessor can make calibration corrections on measured
magnetic field data before transmission.
The Model 1540 system communicates over a bidirectional serial interface using
TTL logic levels and RS-232 levels. Three communication protocols are available:
TTL or RS-232 or RS-422. Select one or more of these communications protocols
when ordering a 1540 system. In addition to the ASCII data transmission mode, the
Model 1540 system has a binary transmission mode and an IEEE 32-bit
transmission mode. These modes are faster than the ASCII mode because

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considerably fewer characters need to be transmitted. The default baud rate is
9600 with one stop bit, no parity and 8 data bits.
An autosend data mode is included in the 1540 software. When this mode is
active, data is repeatedly sent out the serial port automatically after power is
applied to the system.
2 - SYSTEM SPECIFICATIONS
Table 1. System Specifications
Specifications are subject to change without notice.
ELECTRICAL
Input Voltage Range
+4.95 to +12 VDC
Current
55 mA
Digital Output Protocols
RS232 and TTL (RS422 optional)
Digital Output Formats
ASCII and Binary
Baud Rate (User Selectable)
300, 1200, 4800, 9600 (default), 38400
A to D Communications
22-bit Sigma Delta
Data Rate in Autosend Mode
ASCII mode: 10 transmissions/sec
Binary mode: 20 transmissions/sec
ENVIRONMENTAL
Operating Temperature
Range
-25°C to +70°C
Shock
1000 G 1 ms half sine wave
Vibration
10 G RMS random 50 Hz to 500 Hz
PERFORMANCE
Dynamic Range
±6.5x105 nTesla (±0.65 Gauss)
Resolution
10 nTesla (1.0x10-7 Gauss)
Accuracy @ full-scale
±0.5% full-scale
Linearity @ full-scale
±0.05% full-scale
Initial Bias at 25°C
<0.005 mG
Temperature Sensitivity
Scale Factor
±0.05% full-scale/°C
Offset versus Temperature
<0.01 mG/°C
Axis Alignment
Better than ±0.2°

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Alignment of sensor
package with sensor
reference surfaces
Better than ±0.2°
Noise Level
±0.5 nT (±5 μGauss) peak-to-peak
Frequency Response
DC to 400 Hz (-3 db)
Analog Bandwidth
100 Hz
Analog Scale Factor
3 V/G
PHYSICAL
Cylinder size including
connection plate
4.81” (122.17 mm) L x 1” (25.4 mm) dia.
Rectangle size (1540S)
4.75” (120.65 mm) L x 1.15” (29.2 mm) x .95” (24.1
mm)
Weight
85 g
Input/Output Connections
Flying leads (Teflon insulated) #28 gauge >6”
(152.4 mm) length or 9-pin nonmagnetic MDM
connector

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3 - MECHANICAL FEATURES
The cylindrical 1540 has an alignment slot on the top surface. This slot aligns with
the Z+ axis direction. The 1540 coordinate directions are shown in Figure 1. A
magnetic field direction aligned with the axis direction arrows will produce a
positive output voltage.
Mechanical Drawing
Figure 1. Model 1540 Cylindrical Magnetometer

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The Model 1540 is also available in an alternative rectangular package, the Model
1540S, shown in Figure 2. Model 1540S Rectangular Magnetometer Mechanical
DrawingFigure 2. Model 1540S Rectangular Magnetometer Mechanical Drawing
Figure 2. Model 1540S Rectangular Magnetometer Mechanical Drawing
Both the Model 1540 and the Model 1540S have a 9-pin MDM connector for
powering and computer interface.

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4 - ELECTRICAL INTERFACE
The Model 1540 powers from a single input voltage that can range from +4.95 V to
+12 V. Six flying leads (#28 gauge Teflon insulated) are used to connect to the
1540, as shown in Figure 3.
Optionally, a 9-pin MDM connector can be used to connect to the system. The
pinouts for this connector are shown in Table 2for the Model 1540 (cylindrical
barrel) and in Table 3for the Model 1540S (rectangular barrel).
Figure 3. Model 1540 with Leads

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Table 2. Model 1540 Electrical Interface
Flying Lead Wire Color
Function
MDM Connector Pin
Orange
RS-232 serial IN
(or Y RS-422)
1 (black)
Yellow
RS-232 serial OUT
(or Z RS-422)
2 (brown)
Red
+4.95 VDC to +12 VDC
3 (red)
Orange / White
TTL serial IN
(or A RS-422)
4 (orange)
Black
Function
5 (yellow)
Yellow / White
RS-232 serial IN
(or Y RS-422)
6 (green)
Green
RS-232 serial OUT
(or Z RS-422)
7 (blue)
Purple
+4.95 VDC to +12 VDC
8 (purple)
Grey
TTL serial IN
(or A RS-422)
9 (grey)

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Table 3. Model 1540S Electrical Interface
Flying Lead Wire Color
Function
MDM Connector Pin
Black
RS-232 serial IN
(or Y RS-422)
1 (black)
Brown
RS-232 serial OUT
(or Z RS-422)
2 (brown)
Red
+4.95 VDC to +12 VDC
3 (red)
Orange / White
TTL serial IN
(or A RS-422)
4 (orange)
Yellow
Ground
5 (yellow)
Yellow / White
TTL serial OUT
(or B RS-422)
6 (green)
Green
X analog output
(optional)
7 (blue)
Purple
Y analog output
(optional)
8 (purple)
Grey
Z analog output
(optional)
9 (grey)

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4.1 - SETTING UP THE ELECTRICAL
CONNECTIONS
The Model 1540 serial communications interface is provided by the serial in and
serial out lines. These two lines operate at RS-232 or TTL logic levels. Use the TTL
interface to communicate with an internal microprocessor and the RS-232
interface to communicate with a PC through its COM port. The Model 1540 can
also use a four-wire RS-422 serial communication protocol, if the unit has been
wired for RS-422.
Serial communications default to a baud rate of 9600 and use 8 data bits, one
stop bit, and no parity bit. Additional baud rates can be selected by changing the
Model 1540 byte constants.
To connect the RS-232 interface to a PC COM port:
1. PC COM ports use 9-pin D connectors. Connect the 1540 communication
flying leads to a 9-pin PC female D connector as follows:
a. Connect the yellow 1540 wire (or the brown wire for Model 1540S) to
the connector pin 2. This wire provides serial communication from
the 1540.
b. Connect the orange 1540 wire (or the black wire for Model 1540S) to
the connector pin 3. This wire provides serial communication to the
1540.
c. Connect the black 1540 wire (or the yellow wire for Model 1540S) to
the connector pin 5. This wire provides ground for the 1540.
2. Connect +V to the red wire.
3. Connect a standard 9-pin COM port cable between the 1540 D connector
and a PC COM port connector on the computer.
4. Apply power to the + voltage and ground wires.
5. Adjust the input voltage to a value between +5 V and+12 V. The 1540 uses
low dropout linear regulators to produce internal working voltages of ±4.5
V, so the lower the input voltage the lower the power consumed by the
1540.
6. Ensure that the input voltage does not drop below 4.90 volts on the low end
to prevent the internal regulators from dropping out.

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7. Start terminal emulator software, such as Procomm or Windows
HyperTerminal, on the PC. Configure the terminal emulator for direct
connect to an available COM port and select the baud rate 9600 with one
stop bit and no parity.
8. To determine if communication with the 1540 has been established, look at
1540 sign on message that is transmitted at 9600 baud when power is
turned on. Apply power to the system and verify the unit transmits a start
up message similar to the following:
APS: S/N XYZ
VER: 3.85 Bd7716F
See Section 5 - COMPUTER INTERFACE for instructions on
communicating with and configuring the Model 1540.

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5 - COMPUTER INTERFACE
Terminal emulation software, such as Procomm or Windows HyperTerminal, can
be used for communication between a PC and the 1540 system. These programs
translate typed ACSII characters into a serial data stream sent to the 1540 and
also display characters sent from the 1540 on the PC display.
In this mode, whatever you type on the keyboard goes out the selected serial port
(for example, COM 1) and whatever comes in the serial port is displayed on the
computer video display.
If you use HyperTerminal, you must select the proper COM port (for example, COM
1, COM 2...) and set the baud rate to 9600 with one stop bit and no parity. Set the
port for direct connect and turn off handshaking.
Observe the PC display when the 1540 is powered up to see if communications
with the 1540 has been established. The 1540 will transmit a sign on message at
power up, which should appear in readable form on the PC display. If the sign on
message is unreadable, you may have selected an incorrect baud rate on the
computer.
After establishing communication with the 1540, data can be obtained from the
system using sensor commands.
5.1 – MODEL 1540 SENSOR COMMANDS
Sensor commands are used to view or change sensor configuration. Commands
are entered at the command line using terminal emulation software. Some sensor
commands use byte constants (and float constants) to view or change the value
of a constant.
You need to know the following when entering sensor commands.
• Sensor commands are not case sensitive. Examples in Table 4 show
commands entered in uppercase or lowercase.
• Sensor commands begin with a 0 zero (not the letter O).
• Press the Enter key after typing a command on the command line.
The 1540 operating characteristics are controlled by the values of byte constants.
These constants are stored in the system EEROM and can be changed using a two

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step process using sensor commands 0l and 0wc. The two step process is used to
ensure these constants are not accidentally changed.
• Enter the 0l command (zero and the letter L) before using the write
command 0wc. If you see the following error, you didn’t use the 0l
command using the write command.
Err: Not Enabled
Table 4. Model 1540 Commands shows the 1540 sensor commands, command
format and usage and output.
Table 4. Model 1540 Commands
Description
Command Format
Command Response
Send All Data
0SD
0SendData
MX:+0.2589726
MY:-0.3590045
MZ:+0.0540982
T: +23.219
Read a Float Constant
0SC<constant number>F
0SendConstant<>Float
0sc00F
1.00000000E+00
See Table 13. Model 1540 Float Constants
Read All Float Constants
0SC*F
0SendConstant*Float
* is a wildcard.
00: 1.00000000E+00
...
42: 0.00000000E+00
Read a Byte Constant
0SC<constant number>B
0SendConstant<>Byte
0sc00b
01
See Table 5. Commonly Used Byte Constants
Read All Byte Constants
0SC*B
0SendConstant*Byte
* is a wildcard.
00: 01
...
42: 00
Reset A/D
0RA
0ResetAnalogDigital
Done

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Test Serial Port
0TS
0TestSerialPort
OK
Return Software Version
0TV
0TestVersion
APS 0777 Ver:
3.85BD7716F
Enable Writing
0L
Enabled!
Write to a Float Constant
0WC<constant
number>F<value>
0WriteConstant<>Float<>
Done
See Table 13. Model 1540 Float Constants
Write to a Byte Constant
0WC<constant
number>B<number>
0WriteConstant<>Byte<>
Done
See Table 5. Commonly Used Byte Constants
Normal Data
02B02
0WV0
DataDisplayMode =
NORMAL
Done
MX:-0.0032105
MY:-0.0033949
MZ:-0.0062852
T: +24.726
See Section 5.4 - ASCII AND BINARY MODE
Data Only
02B02
0WV1
DataDisplayMode = DATA
ONLY
Done
-0.0032105 -0.0033949 -0.0062852 +24.711

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5.2 – MODEL 1540 BYTE CONSTANTS
System constants include byte constants and float constants.
Byte constants are used to configure the 1540 system and are used when
operating the 1540. See Table 5. Commonly Used Byte Constants
Float constants are used for system calibration, diagnostics, and
troubleshooting and generally not used when operating the 1540. For more
information about float constants, see Table 13. Model 1540 Float Constants
Table 5. Commonly Used Byte Constants
Byte
Constant
Function
00
Command Echo Flag
00 ⁄ 0 Commands are echoed.
00 = 0 Commands are not echoed. Only command responses are
displayed.
01
Autostart Flag
01 = 5A Executes the selected autostart option on power up.
02
Correction Level
02 = 0 A/D Counts
02 = 2 Ortho calibrated data (vector sensor data)
08
Auto Start Mode. On power up start accepting commands and
then:
08
If 01 = 00 and 08 = 10 Send All Data in text mode once.
08
If 01 = 00 and 08 = 11 Send All Data in binary mode once.
08
If 01 = 00 and 08 = 12 Send All Data in IEEE mode once.
08
If 01 = 5A and 08 = 10 Send All Data in text mode in a loop until
AutoStart (01) is not 0x5A.
08
If 01 = 5A and 08 = 11 Send All Data in binary mode in a loop until
AutoStart (01) is not 0x5A.
08
If 01 = 5A and 08 = 12 Send All Data in IEEE mode in a loop until
AutoStart (01) is not 0x5A.
09
Baud Rate Lock
09 ⁄ 5A The sensor will use 9600 baud.
09 = 5A The sensor is using a baud rate other than 9600.

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10
User power on baud rate. -- Use With Caution --
For this target baud rate ==> Use a number below for byte constant
10.
10
75
==> 37
10
150
==> 36
10
300
==> 35
10
600
==> 34
1200
==> 33
2400
==> 32
4800
==> 31
9600
==> 30
19200
==> 5
38400
==> 6
10
Power cycle the unit or the change in baud rate will not take effect.
23
Average control (2, 4, 8, 16).
35
RTS Delay is the time in ~2 millisecond units.
5.3 – MODEL 1540 FLOAT CONSTANTS
In addition to byte constants, the 1540 has a number of float constants. Float
constants are used to store the calibration data in the 1540 Flash memory and are
used for diagnostics and troubleshooting. Although float constants generally
aren’t used when operating the 1540 system,they are included in Appendix A.2 –
MODEL 1540 FLOAT CONSTANTS for reference.
5.4 - ASCII AND BINARY MODE
The Model 1540 sensor transmits data in the following formats: ASCII and binary.
ASCII - The ASCII protocol is based sending ASCII characters (commands) to the
1540 to obtain data. Data transmitted in response to a command is sent out as an
ASCII data stream complete with returns and line feeds so that it can be easily
displayed on a PC display terminal (provided a TTL to RS-232 conversion box is
used). There are two types of ASCII responses, standard and data-only.