Omega Products HHG 21 Installation Manual

Model HHG 21

Manual UN-01-244
April, 2001
Rev. A
 OMEGA
All rights reserved.

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

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

Applications....................................................................... 1-6

SECTION-2 SPECIFICATIONS

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

Standard Transverse Probe.............................................. 2-3

Standard Axial Probe........................................................ 2-4

Optional Probe Extension Cable....................................... 2-5

Zero Flux Chamber............................................................ 2-6

SECTION-3 OPERATING INSTRUCTIONS

Operator Safety................................................................. 3-1

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

Instrument Preparation...................................................... 3-5

Power-Up.......................................................................... 3-7

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

Low Battery Condition....................................................... 3-9

Overrange Condition......................................................... 3-10

UNITS of Measure Selection............................................. 3-11

RANGE Selection.............................................................. 3-12

ZERO Function.................................................................. 3-13

Automatic ZERO Function................................................. 3-14

Manual ZERO Function..................................................... 3-16

Sources of Measurement Errors........................................ 3-18

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

4-1

i

List of Illustrations

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

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

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

Figure 2-1 Standard Transverse Probe....................... 2-3

Figure 2-2 Standard Axial Probe................................. 2-4

Figure 2-3 Optional Probe Extension Cable................ 2-5

Figure 2-4 Zero Flux Chamber.................................... 2-6

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

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

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

Figure 3-4 Battery Installation..................................... 3-5

Figure 3-5 Probe Connection...................................... 3-6

Figure 3-6 Power-Up Display...................................... 3-7

Figure 3-7 Missing Probe Indication............................ 3-8

Figure 3-8 Low Battery Indication................................ 3-9

Figure 3-9 Overrange Indication ................................ 3-10

Figure 3-10 UNITS Function.......................................... 3-11

Figure 3-11 RANGE Function....................................... 3-12

Figure 3-12 Automatic ZERO Function......................... 3-15

Figure 3-13 Manual ZERO Function.............................. 3-17

Figure 3-14 Probe Output versus Flux Angle................ 3-19

Figure 3-15 Probe Output versus Distance................... 3-19

Figure 3-16 Flux Density Variations in a Magnet........... 3-20

ii

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 (M
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 cm

), but the weber (Wb), which is 108 lines, is more

x

2

area. The more

1-1

INTRODUCTION

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

2

. Thus

cm

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. It is important to know that magnetic field
strength and magnetic flux density are not

the same.

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

Figure 1-2

Hall Generator

INTRODUCTION

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.

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.

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:

1-3

INTRODUCTION

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.

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.

1-4

INTRODUCTION

PRODUCT DESCRIPTION

The MODEL HHG-21 GAUSS / TESLAMETER is a portable
instrument that utilizes a Hall probe to measure static (dc)
magnetic flux density in terms of gauss or tesla. The
measurement range is from 0.1 mT (1 G) to 1.999T (19.99 kG).

The MODEL HHG-21 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.

Two measurement ranges can be selected. 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. The “zero” adjustment can
be made manually or automatically.

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

1-5

INTRODUCTION

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 Gauss tesla

2 kG 200 mT 1 G 0.1 mT

20 kG 2 T 10 G 1 mT

ACCURACY (including probe): ± 4 % of reading, ± 3 counts

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

WARMUP TIME TO RATED
ACCURACY: 15 minutes

OPERATING TEMPERATURE: 0 to +50ºC (+32 to +122ºF)

STORAGE TEMPERATURE: -25 to +70ºC (-13 to +158ºF)

BATTERY TYPE: 9 Vdc alkaline (NEDA 1640A)

BATTERY LIFE: 8 hours typical (two batteries)

AUXILIARY POWER: 9 Vdc, 300 mA

AUXILIARY POWER CONNECTOR: Standard 2.5 mm I.D. / 5.5 mm

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

2-1

SPECIFICATIONS

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

2-2