Omega Products HHG-23 Installation Manual

Model HHG-23

GAUSS / TESLA METER

Instruction Manual

This symbol appears on the instrument and probe. It

refers the operator to additional information

contained in this instruction manual, also identified

by the same symbol.

NOTICE:

See Pages 3-1 and 3-2

for SAFETY

instructions prior to first use!

Table of Contents

SECTION-1 INTRODUCTION

Understanding Flux Density.............................................. 1-1

Measurement of Flux Density............................................

Product Description........................................................... 1-5

Applications.......................................................................

SECTION-2 SPECIFICATIONS

Instrument......................................................................... 2-1

Standard Transverse Probe.............................................. 2-5

Standard Axial Probe........................................................ 2-6

Optional Probe Extension Cable....................................... 2-7

Zero Flux Chamber............................................................ 2-8

SECTION-3 OPERATING INSTRUCTIONS

Operator Safety.................................................................

Operating Features........................................................... 3-3

Instrument Preparation......................................................

Power-Up.......................................................................... 3-8

Power-Up Settings............................................................ 3-9

Low Battery Condition....................................................... 3-10

Overrange Condition......................................................... 3-11

AC or DC Measurement Selection..................................... 3-12

UNITS of Measurement Selection..................................... 3-13

RANGE Selection.............................................................. 3-14

HOLD Mode Selection....................................................... 3-16

MIN / MAX Hold Usage...................................................... 3-17

Peak Hold Usage.............................................................. 3-18

ZERO Function.................................................................. 3-20

Automatic ZERO Function................................................. 3-21

Manual ZERO Function..................................................... 3-23

RELATIVE Mode............................................................... 3-25

Automatic RELATIVE Mode.............................................. 3-28

1-2 1-6

3-1 3-6

Manual RELATIVE Mode................................................... 3-30

ANALOG OUTPUT Function............................................. 3-31

Analog Output Usage........................................................ 3-33

Sources of Measurement Errors........................................ 3-35

More details on AC Mode Operation................................. 3-38

More details on DC Mode Operation................................. 3-40

SECTION-4 REMOTE OPERATION

RS-232 Interface Parameters............................................

RS-232 Interface Connection............................................ 4-1

Remote Command Standards........................................... 4-3

Command Format.............................................................. 4-4

Message Terminators........................................................

Error Buffer........................................................................

Status Registers................................................................ 4-5

Status Byte and Request For Service (RQS).................... 4-6

Standard Event Register................................................... 4-9

Measurement Event Register............................................ 4-10

Operation Event Register.................................................. 4-10

Questionable Event Register............................................. 4-11

“Common” Command Syntax............................................ 4-11

“Common” Commands………........................................... 4-13

SCPI Command Syntax..................................................... 4-16

SCPI Commands............................................................... 4-18

Error Messages and Commands....................................... 4-21

Status Commands............................................................. 4-23

MODE Commands............................................................ 4-25

RANGE Commands.......................................................... 4-26

HOLD Commands............................................................. 4-27

ZERO Command............................................................... 4-28

RELATIVE Commands...................................................... 4-28

MEASUREMENT Command............................................. 4-29

ANALOG OUTPUT Command.......................................... 4-30

Intermixing Common and SCPI commands....................... 4-31

Using Query Commands................................................... 4-31

4-1

4-4 4-5

Using the Operation Complete Status............................... 4-32

Example Program.............................................................. 4-33

WARRANTY....................................................................

5-1

List of Tables

Table 4-1 Common Command Summary.................. 4-13

Table 4-2 SCPI Command Summary........................ 4-18

List of Illustrations

Figure 1-1 Flux Lines of a Permanent Magnet............ 1-1

Figure 1-2 Hall Generator............................................

Figure 1-3 Hall Probe Configurations.......................... 1-4

Figure 2-1 Standard Transverse Probe.......................

Figure 2-2 Standard Axial Probe................................. 2-6

Figure 2-3 Optional Probe Extension Cable................

Figure 2-4 Zero Flux Chamber.................................... 2-8

Figure 3-1 Auxiliary Power Connector Warnings.........

Figure 3-2 Probe Electrical Warning........................... 3-2

Figure 3-3 Operating Features.................................... 3-3

Figure 3-4 Battery Installation..................................... 3-6

Figure 3-5 Probe Connection...................................... 3-7

Figure 3-6 Power-Up Display...................................... 3-8

Figure 3-7 Missing Probe Indication............................ 3-9

Figure 3-8 Low Battery Indication................................ 3-11

Figure 3-9 Overrange Indication ................................ 3-11

Figure 3-10 MODE (AC-DC) Function........................... 3-12

Figure 3-11 UNITS Function.......................................... 3-13

Figure 3-12 RANGE Function....................................... 3-15

1-3 2-5 2-7 3-1

iii

Figure 3-13 HOLD Function.......................................... 3-17

Figure 3-14 Automatic ZERO Function......................... 3-22

Figure 3-15 Manual ZERO Function.............................. 3-24

Figure 3-16 RELATIVE Function................................... 3-28

Figure 3-17 Automatic RELATIVE Function................ 3-29

Figure 3-18 Manual RELATIVE Function...................... 3-31

Figure 3-19 OUTPUT Function...................................... 3-32

Figure 3-20 LO and HI Analog Output Displays............ 3-34

Figure 3-21 Adjusting the DC Offset of the Analog

Output........................................................

3-35

Figure 3-22 Probe Output versus Flux Angle................ 3-36

Figure 3-23 Probe Output versus Distance................... 3-37

Figure 3-24 Flux Density Variations in a Magnet........... 3-37

Figure 3-25 Low AC Signal Indication........................... 3-39

Figure 4-1 9-Pin Interface Connector.......................... 4-2

Figure 4-2 Serial Port Connection Schemes............... 4-3

Figure 4-3 Condition, Event and Enable registers.......

Figure 4-4 Status Byte and Enable registers...............

4-6

4-7

Figure 4-5 Standard Event register............................. 4-9

Figure 4-6 Measurement Event register...................... 4-10

Figure 4-7 Operation Event register............................ 4-10

Figure 4-8 Questionable Event register....................... 4-11

Section 1

Introduction

UNDERSTANDING FLUX DENSITY

Magnetic fields surrounding permanent magnets or electrical conductors can be visualized as a collection of magnetic flux lines; lines of force existing in the material that is being subjected to a magnetizing influence. Unlike light, which travels away from its source indefinitely, magnetic flux lines must eventually return to the source. Thus all magnetic sources are said to have two poles. Flux lines are said to emanate from the “north” pole and return to the “south” pole, as depicted in Figure 1-1.

Figure 1-1

Flux Lines of a Permanent Magnet

One line of flux in the CGS measurement system is called a maxwell (Mx), but the weber (Wb), which is 108 lines, is more commonly used.

Flux density, also called magnetic induction, is the number of flux lines passing through a given area. It is commonly assigned the symbol “B” in scientific documents. In the CGS system a gauss (G) is one line of flux passing through a 1 cm2 area. The more

1-1

INTRODUCTION

commonly used term is the tesla (T), which is 10,000 lines per cm2 . Thus

1 tesla = 10,000 gauss 1 gauss = 0.0001 tesla

Magnetic field strength is a measure of force produced by an electric current or a permanent magnet. It is the ability to induce a magnetic field “B”. It is commonly assigned the symbol “H” in scientific documents. The unit of “H” in the CGS system is an oersted (Oe), but the ampere/meter (A/m) is more commonly used. The relationship is

1 oersted = 79.6 ampere/meter

1 ampere/meter = 0.01256 oersted

It is important to know that magnetic field strength and magnetic flux density are not the same. The only time the two are considered equal is in free space (air). Only in free space is the following relationship true:

1 G = 1 Oe = 0.0001 T = 79.6 A/m

MEASUREMENT OF FLUX DENSITY

A device commonly used to measure flux density is the Hall generator. A Hall generator is a thin slice of a semiconductor

material to which four leads are attached at the midpoint of each edge, as shown in Figure 1-2.

1-2

INTRODUCTION

Figure 1-2

Hall Generator

A constant current (Ic) is forced through the material. In a zero magnetic field there is no voltage difference between the other two edges. When flux lines pass through the material the path of the current bends closer to one edge, creating a voltage difference known as the Hall voltage (Vh). In an ideal Hall generator there is a linear relationship between the number of flux lines passing through the material (flux density) and the Hall voltage.

The Hall voltage is also a function of the direction in which the flux lines pass through the material, producing a positive voltage in one direction and a negative voltage in the other. If the same number of flux lines pass through the material in either direction, the net result is zero volts. This sensitivity to flux direction makes it possible to measure both static (dc) and alternating (ac) magnetic fields.

The Hall voltage is also a function of the angle at which the flux lines pass through the material. The greatest Hall voltage occurs when the flux lines pass perpendicularly through the material. Otherwise the output is related to the cosine of the difference between 90° and the actual angle.

1-3

INTRODUCTION

The sensitive area of the Hall generator is generally defined as the largest circular area within the actual slice of the material. This active area can range in size from 0.2 mm (0.008”) to 19 mm (0.75”) in diameter. Often the Hall generator assembly is too fragile to use by itself so it is often mounted in a protective tube and terminated with a flexible cable and a connector. This assembly, known as a Hall probe, is generally provided in two configurations:

TRANSVERSE PROBE

AXIAL PROBE

Figure 1-3

Hall Probe Configurations

In “transverse” probes the Hall generator is mounted in a thin, flat stem whereas in “axial” probes the Hall generator is mounted in a cylindrical stem. The axis of sensitivity is the primary difference, as shown by “B” in Figure 1-3. Generally transverse probes are used to make measurements between two magnetic poles such as those in audio speakers, electric motors and imaging machines. Axial probes are often used to measure the magnetic field along the axis of a coil, solenoid or traveling wave tube. Either probe can be used where there are few physical space limitations, such as in geomagnetic or electromagnetic interference surveys.

1-4

INTRODUCTION

Handle the Hall probe with care. Do not bend the stem or

apply pressure to the probe tip as damage may result. Use

the protective cover when the probe is not in use.

PRODUCT DESCRIPTION

The MODEL HHG-23 GAUSS / TESLAMETER is a portable instrument that utilizes a Hall probe to measure magnetic flux density in terms of gauss, tesla or ampere/meter. The measurement range is from 0.01 mT (0.1 G or 0.01 kA/m) to

2.999T (29.99 kG or 2387 kA/m). The instrument is capable of measuring static (dc) magnetic fields and alternating (ac) fields.

The MODEL HHG-23 consists of a palm-sized meter and various detachable Hall probes. The meter operates on standard 9 volt alkaline batteries or can be operated with an external ac-to-dc power supply. A retractable bail allows the meter to stand upright on a flat surface. A notch in the bail allows the meter to be wall mounted when bench space is at a premium. The large display is visible at considerable distances. The instrument is easily configured using a single rotary selector and two pushbuttons.

Three measurement ranges can be selected or the meter can automatically select the best range based on the present flux density being measured. A “zero” function allows the user to remove undesirable readings from nearby magnetic fields (including earth’s) or false readings caused by initial electrical offsets in the probe and meter. Included is a “zero flux chamber” which allows the probe to be shielded from external magnetic fields during this operation. Another feature called “relative mode” allows large flux readings to be suppressed so that small variations within the larger field can be observed directly. Both the “zero” and “relative” adjustments can be made manually or automatically.

1-5

INTRODUCTION

Other features include three “hold” modes, allowing either the arithmetic maximum, minimum or true peak values to be held indefinitely until reset by the user. An analog signal is available from a standard BNC connector that is representative of the magnetic flux density signal and is calibrated to ± 3 volts full scale in dc mode or 3 Vrms in ac mode. This output can be connected to a voltmeter, oscilloscope, recorder or external analog-to-digital converter.

The meter can be fully configured and flux density readings acquired from a remote computer or PLC using the RS-232 communications port. This is a standard 9-pin “D” connector commonly used in personal computers. The commands follow widely accepted protocols established by the IEEE-488.2 and SCPI-1991 standards.

The meter, probes and accessories are protected when not in use by a sturdy carrying case.

APPLICATIONS

• Sorting or performing incoming inspection on permanent

magnets, particularly multi-pole magnets.

• Testing audio speaker magnet assemblies, electric motor

armatures and stators, transformer lamination stacks, cut toroidal cores, coils and solenoids.

• Determining the location of stray fields around medical

diagnostic equipment.

• Determining sources of electromagnetic interference.

• Locating flaws in welded joints.

• Inspection of ferrous materials.

• 3-dimensional field mapping.

• Inspection of magnetic recording heads.

1-6

Section 2

Specifications

INSTRUMENT

RANGE RESOLUTION

gauss tesla A/m gauss tesla A/m

300 G

3 kG 300 mT 238 kA/m

30 kG

ACCURACY (reading on display and from RS-232 port, including probe)

dc mode: ± 1 % of reading, ± 3 counts ac mode:

20 - 10,000 Hz: ± 2.5 % of reading, ± 5 counts 10,000 - 20,000 Hz: ± 5 % of reading, ± 5 counts

ACCURACY (analog output, including probe)

dc mode: ± 1 % of reading, ± 5 mV. ac mode, low range:

20 - 2000 Hz: ± 3 % of reading, ± 5 mV 10,000 Hz: - 3 dB

ac mode, mid and high range: 20 - 4000 Hz: ± 3 % of reading, ± 5 mV 15,000 Hz: - 3 dB

WARMUP TIME TO RATED ACCURACY: 15 minutes

30 mT

3 T 2388 kA/m

23 kA/m

0.1 G 1 G

10 G

0.01 mT 0.01 kA/m

0.1 mT 1 mT

0.1 kA/m 1 kA/m

2-1

SPECIFICATIONS

MIN / MAX HOLD ACQUISITION TIME: dc mode: 180 ms typical

ac mode: 300 ms typical

PEAK HOLD ACQUISITION TIME: dc mode: 1 ms typical

ac mode: 1 ms typical

ANALOG OUTPUT SCALING: dc mode: ± 3 Vdc ac mode: 3 Vrms

ANALOG OUTPUT NOISE: 4 mV rms typical ANALOG OUTPUT LOAD: 10 kΩ min, 100 pF max. ACCURACY CHANGE WITH

TEMPERATURE (not including probe): ± 0.02 % / ºC typical

BATTERY TYPE: 9 Vdc alkaline (NEDA 1640A) BATTERY LIFE: 8 hours typical (two batteries,

analog output and RS-232 port not used)

AUXILIARY POWER: 6 to 12 Vdc, 300 mA minimum. AUXILIARY POWER CONNECTOR: Standard 2.5 mm I.D. / 5.5 mm

O.D. connector. Center post is positive (+) polarity.

ANALOG OUTPUT CONNECTOR: BNC OPERATING TEMPERATURE: 0 to +50ºC (+32 to +122ºF)

2-2

SPECIFICATIONS

STORAGE TEMPERATURE: -25 to +70ºC (-13 to +158ºF) METER DIMENSIONS: Length: 13.2 cm (5.2 in)

Width: 13.5 cm (5.3 in) Height: 3.8 cm (1.5 in)

WEIGHT: Meter w/batteries: 400 g (14 oz.)

Shipping: 1.59 kg (3 lb., 8 oz.) REGULATORY INFORMATION:

Compliance was demonstrated to the following specifications as listed in the official Journal of the European Communities:

EN 50082-1:1992 Generic Immunity

IEC 801-2:1991 Electrostatic Discharge Second Edition Immunity IEC 1000-4-2:1995

ENV 50140:1993 Radiated Electromagnetic IEC 1000-4-3:1995 Field Immunity

EN 50081-1:1992 Generic Emissions

EN 55011:1991 Radiated and Conducted Emissions

2-3

SPECIFICATIONS

COMMUNICATIONS PORT: Format: RS-232C

Lines supported: Transmit, receive, common. Connector type: 9-pin “D” female Cable length: 3 m (9.8 ft.) maximum Receive input resistance: 3 kΩ minimum Receive voltage limit: ± 30 V maximum Transmit output voltage: ± 5 V min, ± 8 V typical Baud rate: 2400 Stop bits: 1 Character length: 8 Parity: None Standards supported: IEEE-1987.2, SCPI-1991

EMC APPLICATION NOTE

Use only high quality, double shielded cables for RS-232 connection. Keep the length of the cables less than 3 meters (9.8 ft.). Long cables (>3m) with insufficient EMI shielding can cause excessive emissions or may be susceptible to external interference.

2-4

SPECIFICATIONS

STANDARD TRANSVERSE PROBE

MODEL NUMBER: STD58-0404 FLUX DENSITY RANGE: 0 to ± 3 T (0 to ± 30 kG) FREQUENCY BANDWIDTH: 0 - 20 kHz OFFSET CHANGE WITH

TEMPERATURE: ± 30 µT (300 mG) / ºC typical ACCURACY CHANGE WITH

TEMPERATURE: - 0.05% / ºC typical OPERATING TEMPERATURE RANGE: 0 to +75 ºC (+32 to +167ºF) STORAGE TEMPERATURE RANGE: -25 to +75 ºC (-13 to +167ºF)

Figure 2-1

Standard Transverse Probe

2-5

SPECIFICATIONS

STANDARD AXIAL PROBE

MODEL NUMBER: SAD58-1904 FLUX DENSITY RANGE: 0 to ± 3 T (0 to ± 30 kG) FREQUENCY BANDWIDTH: 0 - 20 kHz OFFSET CHANGE WITH

TEMPERATURE: ± 30 µT (300 mG) / ºC typical ACCURACY CHANGE WITH

TEMPERATURE: - 0.05% / ºC typical OPERATING TEMPERATURE RANGE: 0 to +75 ºC (+32 to +167ºF) STORAGE TEMPERATURE RANGE: -25 to +75 ºC (-13 to +167ºF)

2-6

Figure 2-2

Standard Axial Probe

SPECIFICATIONS

OPTIONAL PROBE EXTENSION CABLE

MODEL NUMBER: X5000-0006 OPERATING TEMPERATURE RANGE: 0 to +75 ºC (+32 to +167ºF) STORAGE TEMPERATURE RANGE: -25 to +75 ºC (-13 to +167ºF)

Figure 2-3

Optional Probe Extension Cable

2-7

SPECIFICATIONS

ZERO FLUX CHAMBER

MODEL NUMBER: YA-111 CAVITY DIMENSIONS:

Length: 50.8 mm (2”) Diameter: 8.7 mm (0.343”)

ATTENUATION: 80 dB to 30 mT (300 G) PURPOSE: To shield the probe from

external magnetic fields during the ZERO or RELATIVE operations.

2-8

Figure 2-4

Zero Flux Chamber

Section 3

Operating Instructions

OPERATOR SAFETY

Do not connect the auxiliary power connector to an ac power

source. Do not exceed 15 Vdc. Do not reverse polarity. Use

only an ac-to-dc power supply certified for country of use.

Figure 3-1

Auxiliary Power Connector Warnings

3-1

OPERATING INSTRUCTIONS

Do not allow the probe to come in contact with any voltage

source greater than 30 Vrms or 60 Vdc.

Figure 3-2

Probe Electrical Warning

This instrument may contain ferrous components which will exhibit attraction to a magnetic field. Care should be utilized when operating the instrument near large magnetic fields, as

pull-in may occur. Extension cables are available to increase the probe cable length, so that the instrument can remain in a

safe position with respect to the field being measured with

the probe.

3-2

OPERATING INSTRUCTIONS

OPERATING FEATURES

Figure 3-3

Operating Features

1 Display. Liquid crystal display (LCD). 2 Manual ZERO / RELATIVE Control. In the ZERO and

RELATIVE modes of operation the user can manually adjust the zero or relative point using this control.

3 Function Selector. This control allows the operator to change the meter’s range, units of measure, ac or dc measurement, hold modes and operation of the analog output. It also engages the ZERO, RELATIVE and MEASURE modes of operation.

4 RS-232 Port. Shielded 9-pin “D” connector supporting RS-232-C serial communications.

5 Battery Compartment Cover. This cover slides open to allow one or two 9 volt batteries to be installed.

3-3

OPERATING INSTRUCTIONS

6 Power Switch. Push-on / push-off type switch to apply

power to the meter. 7 SELECT Switch. Momentary pushbutton used in

conjunction with the Function Selector 3 to configure the meter’s range, units of measure, ac or dc measurement, hold modes and operation of the analog output.

8 AUTO/HOLD RESET Switch. Momentary pushbutton used to reset the held reading when one of the HOLD modes is being used, or to start an automatic ZERO or RELATIVE operation when in the ZERO or RELATIVE modes.

9 Auxiliary Power Connector. This is an industry standard

2.5 mm I.D. / 5.5 mm O.D. dc power connector. The meter will accept a dc voltage in the range of 6 - 15 Vdc at 300 mA minimum current. The center pin is positive (+). The internal batteries are disconnected when using this connector.

Do not connect the auxiliary power connector to an ac power

source. Do not exceed 15 Vdc. Do not reverse polarity. Use

only an ac-to-dc power supply certified for country of use.

3-4

OPERATING INSTRUCTIONS

10 Analog Output Connector. A voltage signal

representative of the magnetic flux density being measured is available at this BNC connector. Calibration is set to ± 3.0 V full scale dc or 3.0 Vrms ac, depending upon the mode of operation . Minimum load is 10 kΩ. The analog output will be active when the ANALOG ON/OFF function has been turned ON using the Function Selector 3 .

11 Probe Connector. The Hall probe or probe extension cable plugs into this connector and locks in place. To disconnect, pull on the body of the plug, not the cable !

12 Meter Stand. Retractable stand that allows the meter to stand upright when placed on a flat surface. A notch in the stand allows the meter to be mounted to a vertical surface.

3-5

OPERATING INSTRUCTIONS

INSTRUMENT PREPARATION

1) With the power switch turned off (POWER pushbutton in the full up position) apply pressure to the battery compartment cover at the two points shown in Figure 3-4. Slide the cover open and remove.

2) Install one or two 9 volt alkaline batteries (two batteries will provide longer operating life). The battery compartment is designed so that the battery polarity cannot be reversed. Reinstall the battery compartment cover.

3-6

Figure 3-4

Battery Installation

OPERATING INSTRUCTIONS

3) If using an ac-to-dc power supply review Figure 3-1 for safety notes and the SPECIFICATIONS section for voltage and current ratings. When using a power supply the batteries are automatically disconnected.

4) Install the probe or probe extension cable by matching the key way in the connector to that in the mating socket in the meter. The connector will lock in place. To disconnect, pull on the body of the plug, not the cable!

Figure 3-5

Probe Connection

3-7

OPERATING INSTRUCTIONS

POWER-UP

Depress the POWER switch. There will be a momentary audible beep and all display segments will appear on the display.

Figure 3-6

Power-Up Display

The instrument will conduct a self test before measurements begin. If a problem is detected the phrase “Err” will appear on the display followed by a 3-digit code. The circuitry that failed will be retested and the error code will appear after each failure. This process will continue indefinitely or until the circuitry passes the test. A condition in which a circuit fails and then passes should not be ignored because it indicates an intermittent problem that should be corrected.

If the self test is successful the meter will perform a self calibration. During this phase the meter will display the software revision number, such as “r 1.0”. Calibration will halt if there is no Hall probe connected. Until the probe is connected the phrase “Err” will appear accompanied by a flashing “PROBE” annunciator as shown in Figure 3-7.

3-8

OPERATING INSTRUCTIONS

Figure 3-7

Missing Probe Indication

After power-up the position of the FUNCTION selector switch will determine what happens next. For instance if the selector is in the RANGE position the meter will wait for the user to change the present range. If in the MEASURE position flux density measurements will begin.

Allow adequate time for the meter and probe to reach a stable temperature. See the SPECIFICATIONS section for specific information.

POWER-UP SETTINGS The meter permanently saves certain aspects of the instrument’s

setup and restores them the next time the meter is turned on. The conditions that are saved are:

RANGE setting (including AUTO range) MODE (ac or dc) UNITS of measure (gauss, tesla or ampere/meter) HOLD mode (min, max or peak)

3-9

OPERATING INSTRUCTIONS

Other aspects are not saved and default to these conditions: RELATIVE mode (turned OFF)

RELATIVE value (set to 0) ZERO mode (inactive) OUTPUT function (turned OFF and output set to 0 Vdc)

NOTE: The present setup of the instrument is saved only when the FUNCTION selector is returned to the MEASURE position. For example assume the meter is in the MEASURE mode on the 30 mT range. The FUNCTION selector is now turned to the RANGE position and the 300 mT range is selected. The meter is turned off and on again. The meter will be restored to the 30 mT range because the FUNCTION selector was never returned to the MEASURE mode prior to turning it off.

LOW BATTERY CONDITION

The meter is designed to use one or two standard 9V alkaline batteries (two batteries will provide longer operating life). When the battery voltage becomes too low the battery symbol on the display will flash, as shown in Figure 3-8. Replace the batteries or use an external ac-to-dc power supply.

Instrument specifications are not guaranteed when a low

battery condition exists !

3-10

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