Omega Products HHMA2 Installation Manual

HHMA2

DC / TRUE RMS AC

NON-CONTACT MILLIAMMETER

Instruction Manual

Manual UN-01-249
Item 359934
April, 1999
Rev. -­OMEGA Engineering Inc.
All rights reserved.

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

DESCRIPTION....................................................... 1-1

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

SECTION-2 SPECIFICATIONS

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

SECTION-3 OPERATING INSTRUCTIONS

OPERATOR SAFETY....................................................... 3-1

OPERATING FEATURES................................................. 3-3

MEASUREMENT PROCEDURES..................................... 3-7

Instrument Preparation............................... 3-7

DC Current Measurements......................... 3-8

Low Frequency AC Current

Measurements........................................ 3-10

High Frequency AC Current

Measurements........................................ 3-11

Measurement Hints.................................... 3-11

GENERAL MAINTENANCE............................................... 3-13

SECTION-4 WARRANTY

i

List of Tables

Table 2-1 HHMA2 Specifications........................ 2-1

List of Illustrations

Figure 3-1 Conductor Voltage Limit Warning ........ 3-1

Figure 3-2 Bare Conductor Warning...................... 3-2

Figure 3-3 Auxiliary Power Connection Warnings.. 3-2

Figure 3-4 Product Features.................................. 3-3

Figure 3-5 Battery Installation and AC Adapter

Connection........................................

Figure 3-6 Probe Connection................................. 3-8

Figure 3-7 DC Zeroing Process.............................. 3-9

3-7

ii

Section 1

Introduction

DESCRIPTION

The HHMA2 is a battery-powered, clamp-on instrument that
measures dc and ac current as low as 1 mA and as high as 2000
mA, at frequencies up to 100 kHz. The HHMA2 consists of a
palm-sized meter and a detachable probe. The probe clamps
around the conductor to be measured. There is no need to
disconnect the conductor or to make physical contact with the
circuit being measured. The current-carrying conductor is
surrounded by a magnetic field that is proportional to the amount
of current that is flowing through it. The probe senses the
magnetic field and provides a signal to the meter. The meter
then translates this signal into a milliamp current value.

The probe features a unique aperture mechanism that retracts
easily and closes smoothly. The probe can accommodate
conductors up to 5.3 mm (0.21 in) in diameter.

The meter operates on two standard 9-volt alkaline batteries, or it
can be operated with an ac adapter. Two ranges can be selected
(199.9 mA or 1999 mA full scale) in addition to three modes of
measurement: dc, low-frequency ac or high-frequency ac. The
meter contains a 3 ½ digit display that provides dc and true rms
ac readings. In addition, an analog output provides a 1 mV / mA
voltage signal proportional to the current being measured. This
output can be connected to a voltmeter, oscilloscope or recorder.

The meter, probe and accessories are protected between uses
by a sturdy carrying case.

1-1

INTRODUCTION

APPLICATIONS

• Diagnosis and general maintenance of 4 - 20 mA process

control loops.

Troubleshooting of low-to-medium current devices in

•

automobiles, such as lamps, relays, motors and
communications lines.

Detection of leakage current in battery-operated devices.

•

Monitoring charge current in battery charging systems.

•

Testing of low level signal lines in electronic equipment.

•

Monitoring serial communications bit streams (RS-232).

•

1-2

Section 2

Specifications

ELECTRICAL

Range / Resolution: (displayed reading)

LOW (200 mA): 0.1 to 199.9 mA dc or rms ac
HIGH (2000 mA): 1 to 1999 mA dc or ac peak

Accuracy: (% of reading, ± 3 counts for the displayed reading or

± 0.15% of range for the analog output.
Meter zeroed prior to measurement in DC or
AC-LOW mode.)

dc: 1%
ac low: 2%
ac high (200 Hz - 400 Hz): 4%
ac high (400 Hz - 40 kHz): 2%
ac high (40 kHz - 100 kHz): 3%

Repeatability: 0.5% of reading, ± 3 counts for the

displayed reading or ± 0.15% of
range for the analog output.

Output noise: less than 100 µV rms

2-1

Table 2-1 HHMA2 Specifications

2-2

Frequency Range: (displayed reading)

dc: 0 Hz

ac low: 10 Hz to 200 Hz
ac high: 200 Hz to 100 kHz

Frequency Range: (analog output)

dc: 0 Hz to 200 Hz

ac low: 0 Hz to 200 Hz
ac high: 200 Hz to 100 kHz

Frequency response: (-3 dB point)

ac low: 400 Hz
ac high: 250 kHz

Rise Time:

ac low: 750 µs.
ac high: 1 µs.

Analog output scaling: 1 mV / mA

Analog output load: 10 kΩ min., 100 pF max.

Current • Frequency Limit: 80 A • kHz maximum

Probe Inductance: less than 1 µH

2-3

Table 2-1 HHMA2 Specifications (cont.)

2-4

GENERAL

Battery Type: 9 Vdc alkaline (NEDA 1640A)

(two required)

Battery Life: 15 hours typical (based on equal
usage of all three modes: DC,
AC-LOW and AC-HIGH).

Auxiliary Power: 15 to 18 Vdc, 100 mA minimum.
(Certified for the country of use)

Auxiliary Power 2.5 mm, center post is positive (+)
Connector: polarity.

Analog Output Connector: BNC

Probe aperture size: 5.3 mm (0.21 in)

Probe dimensions:
Length: 15.9 cm (6.25 in)
Diameter: 3.0 cm (1.2 in)

Meter dimensions:
Length: 13.2 cm (5.2 in)

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

Weight:
Probe/Cable: 178.6 g (6.3 oz)

Meter w/batteries: 357.2 g (12.6 oz)
Shipping: 1.758 kg (3 lb, 14 oz)

2-5

Table 2-1 HHMA2 Specifications (cont.)

Safety: IEC 1010 Cat.2 (300 volt), Pollution Degree 2
Standards: EN61010-1/1993
EN61010-1 A2/1995
EN61010-2-032/1995

EMC: RF Immunity: EN50140:1993
IEC 1000-4-3:1995

ESD Immunity IEC 801-2:1991
IEC 1000-4-2:1995

Radiated & Conducted Emission:
EN55011:1991

Temperature coefficient: 0.01% / ºC

Operating temperature range: 0 to +50 ºC (+32 to +122 ºF)
Storage temperature range: -25 to +70 ºC (-13 to +158ºF)

Reference Condition: This instrument is designed to comply with

IEC1010-1, Installation Category II, 300V, Pollution Degree 2 and
is for use with conductors having a suitable insulation. This
instrument is designed to be safe at least under the following
conditions:

- Indoor use;

- Altitude up to 2000 m;

- Temperature 0 to 50 C

- Maximum relative humidity 80% for temperatures up to 31C
decreasing linearly to 50% relative humidity at 40C.

2-6

Table 2-1 HHMA2 Specifications (cont.)

2-7

Section 3

Operating Instructions

OPERATOR SAFETY

This symbol appears on the instrument and probe. It refers the
operator to additional information contained in this instruction
manual, where it is identified by the same symbol.

The following safety rules must be followed during the operation
and servicing of the HHMA2. Strict adherence to these rules is
essential for safe operation. OMEGA Engineering, Inc. assumes
no liability for the failure to comply with these rules.

Do not clamp around conductors with voltages equal to or

exceeding 300 Vdc or rms ac.

Fig. 3-1

Conductor Voltage Limit Warning

3-1

OPERATING INSTRUCTIONS

Do not clamp the probe around bare conductors. Conductor
must have a suitable insulation.

Fig. 3-2

Bare Conductor Warning

Do not connect the auxiliary power connector to an ac power
source. Do not exceed 18 Vdc. Do not reverse the polarity. Use
only AC power supply certified for country of use.

3-2

Fig. 3-3

Auxiliary Power Connector Warnings

OPERATING FEATURES

OPERATING INSTRUCTIONS

Fig. 3-4

Product Features

1 Aperture trigger. When the trigger is pulled back, the
aperture 2 opens. When the trigger is released, the
aperture will close slowly. Do not force the aperture

closed by pushing on the trigger or damage may occur.

2 Probe aperture. The aperture can accommodate up to

5.33 mm (0.21 inch) diameter conductors. The aperture
is opened by pulling back on the trigger 1 . It is
important that the aperture be free of contaminants that
might prevent the aperture from fully closing; otherwise,

3-3

OPERATING INSTRUCTIONS

the earth’s magnetic field may affect instrument accuracy.
Use only isopropyl alcohol and a cotton swab to clean the
aperture area. Never use a sharp instrument or a stiff

brush to clean the aperture or damage will occur !

3 Display. LCD containing 3 ½ digits of numeric
information and the LOW BAT annunciator. In all modes, the
value displayed is in milliamps-dc current in the DC mode and
true rms ac current in the AC-LOW and AC-HIGH modes.

4 Coarse zero adjust control. With the aperture closed

and no current flowing through the aperture, adjust this
control so that the displayed reading is as close to zero as
possible.

5 Fine zero adjust control. With the aperture closed and

no current flowing through the aperture, adjust this control
so that the displayed reading is zero. If this is not
possible, readjust the coarse zero control 4 .

6 Power switch. Sliding the switch to the “ON” position
turns the meter on.

7 Range switch. The range switch affects the displayed
reading only. Sliding the switch to the “200 mA” position
results in a measurement range of 0.0 - 199.9 mA.
Sliding the switch to the “2000 mA” position results in a
measurement range of 0 - 1999 mA. The analog output is
not affected by the range switch and always provides an
output of 1 mV / mA.

3-4

OPERATING INSTRUCTIONS

8 DC/AC-LOW/AC-HIGH switch. This three-position switch

selects the type of current to be measured. It affects both
the displayed reading and the analog output, although
differently.

Sliding the switch to the “DC” position allows for the
display of dc current. The analog output will contain both
the dc component and any ac component up to
frequencies of 200 Hz.

Sliding the switch to the “AC-LOW” position allows for
the display of rms ac current in the frequency range of
10 Hz to 200 Hz. The analog output will contain both the
dc component and any ac component up to frequencies of
200 Hz.

Sliding the switch to the “AC-HIGH” position allows for the
display of rms ac current in the frequency range of 200 Hz
to 100 kHz. The analog output will contain any ac
component in the same frequency range.

9 Auxiliary power connector. This is an industry-standard,

2.5 mm, dc power connector. The HHMA2 will accept
a dc voltage in the range of 15 - 18 Vdc at 100 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 18 Vdc. Do not reverse the
polarity.

3-5

OPERATING INSTRUCTIONS

10 Analog output connector. A voltage signal

representative of the current being measured is available
at this BNC connector. Calibration is set to 1 mV / mA.
Minimum load is 10 kΩ.

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

12 Batteries. Install two 9-Volt alkaline batteries (NEDA­ 1640A) in the positions shown. The connections are
polarized to prevent accidental battery reversal. It is
suggested that both batteries be replaced at the same
time with new batteries.

13 Battery compartment door. This cover slides off as
shown in Figure 3-4.

14 Meter stand. This retractable stand allows the meter
to be viewed when placed on a horizontal surface. A
notch in the stand allows the meter to be mounted to a
vertical surface.

3-6

OPERATING INSTRUCTIONS

MEASUREMENT PROCEDURES

Instrument Preparation

1) With the power switch in the “OFF” position, remove the
battery compartment door by pressing down at the two points
shown in Figure 3-5 and sliding the door off. Install two 9-Volt
alkaline batteries. Replace the battery compartment door.

NOTE: Batteries are not required if using an ac adapter.

Fig. 3-5

Battery Installation and AC Adapter Connection

2) Connect the probe by matching the keyway on the probe’s
connector to that of the mating socket in the meter. Push the
connector in until it locks in place.

3-7

OPERATING INSTRUCTIONS

NOTE: The probe and meter are calibrated together. Probes
are not interchangeable. If the probe has to be replaced, the
meter must be recalibrated with the new probe.

Fig. 3-6

Probe Connection

3) Slide the power switch to the “ON” position and allow the
probe to settle for a few seconds.

DC Current Measurements

Initially, the probe and meter may contain magnetic and electrical
offsets that will be displayed as an actual current reading. This
“false” reading must be removed to obtain a true current reading.
This process is called “zeroing” and should be performed as
follows, referring to Figure 3-7:

1) Slide the DC/AC-LOW/AC-HIGH switch to “DC”.

2) Select the desired range, either “200 mA” or “2000 mA”.

3-8

OPERATING INSTRUCTIONS

3) Open and close the aperture one time. Do not clamp around
the conductor to be measured. Stay away from sources of strong
magnetic fields.

4) Using the smaller coarse “zero” knob, adjust the reading to as
close to zero as possible.

5) Using the larger fine “zero” knob, adjust the reading to zero.
Readjust the coarse knob if this is not possible.

6) Pull back the trigger and clamp onto the conductor to be
measured. Release the trigger and allow the aperture to fully
close before taking a reading. Once the aperture closes, do

not push the trigger or drop or bump the probe against any
other object. Any mechanical stress or shock can cause a dc
offset and thus an error in the reading.

NOTE:

When the meter is first turned on, the aperture should

be opened and closed at least once before zeroing.

Fig. 3-7

DC Zeroing Process

3-9

OPERATING INSTRUCTIONS

If the reading appears as a “1“, the current level exceeds the
selected range of the meter. Select the “2000 mA” range, and
repeat Steps 3 through 6 above. If already on the “2000 mA”
range, the current exceeds the measurement range of this
instrument. An arrow appears on the probe near the aperture. If
the reading is positive, the current is flowing in the direction of the
arrow. If negative, the current is flowing in the opposite direction.

A voltmeter or oscilloscope can be connected to the analog
output connector. The output is a voltage proportional to the
current being measured and is scaled to 1 mV / mA, regardless of
the range switch setting. This signal will contain the dc level as
well as any ac components up to 200 Hz. The coarse and fine
“zero” adjustments also affect the dc level of the analog output.

Low Frequency AC Current Measurements

To measure ac current in the frequency range of 10 Hz to 200
Hz, select the “AC-LOW” setting and select the desired range
(“200 mA” or “2000 mA”). Clamp around the conductor. The
displayed readings will be the true rms values of the ac current.
The coarse and fine “zero” adjustments have no effect on the
displayed readings.

A voltmeter or oscilloscope can be connected to the analog
output connector. The output is a voltage proportional to the
current being measured and is scaled to 1 mV / mA, regardless of
the range switch setting. This signal will contain the dc level as
well as any ac components up to 200 Hz. Since the coarse and
fine “zero” adjustments affect the dc level of the analog output,
the meter must be zeroed. This procedure is described in the
previous section entitled “DC Current Measurement”, Steps 3
through 6.

3-10

OPERATING INSTRUCTIONS

High Frequency AC Current Measurements

To measure ac current in the frequency range of 200 Hz to 100
kHz, select the “AC-HIGH” setting and select the desired range
(“200 mA” or “2000 mA”). Clamp around the conductor. The
displayed readings will be the true rms values of the ac current.
The coarse and fine “zero” adjustments have no effect on the
displayed readings.

A voltmeter or oscilloscope can be connected to the analog
output connector. The output is a voltage proportional to the
current being measured and is scaled to 1 mV / mA, regardless of
the range switch setting. This signal will contain only ac
components from 200 Hz to 100 kHz. The coarse and fine “zero”
adjustments have no effect on the analog output.

Prolonged operation under conditions such that the product of

•

the current and frequency exceeds 80 A

kHz can cause

permanent damage to the probe!

Measurement Hints

• It is important that the

aperture be free of
contaminants that might
prevent the aperture from
fully closing, otherwise the
earth’s magnetic field may
affect instrument accuracy.
Use only isopropyl alcohol
and a cotton swab to clean
the sensing element surfaces. Never use a sharp instrument
or a stiff brush to clean the aperture or damage will occur !

3-11

OPERATING INSTRUCTIONS

• In the “DC” current mode, the process of “zeroing” the meter

is vital for accurate measurements. The meter should be
zeroed each time prior to clamping on to the conductor.
Check the zero point often. When the meter is first turned on,
the aperture should be opened and closed at least one time
before zeroing.

• Once the aperture closes, do not push the trigger or drop or

bump the probe against any other object. Any mechanical
shock or stress can cause a dc offset and thus an error in the
reading. If this happens, remove the probe from the
conductor, zero the meter and repeat the measurement.

• Whenever possible, allow current to flow through the

conductor before clamping the probe around the conductor.
In the “DC” current mode, sudden large changes in the dc
current, or current exceeding the range of the instrument,
can induce an offset that will affect the accuracy of the meter,
or could cause the meter to overrange. Examples include
motor or lamp circuits, where inrush currents far exceed the
normal operating current. If this occurs, open and close the
probe aperture and rezero the meter, or allow the inrush to
occur and then clamp the probe around the conductor.

• The sensitivity of the measurement can be increased by

wrapping several turns of the same conductor through the
aperture. The turns must be circulating in the same direction.
The actual current can be calculated by dividing the reading
by the number of turns. For instance, suppose there are 8
turns and the reading is 3.2 mA. The actual current flow is

3.2 mA / 8 = 0.4 mA

• If the conductor being measured is too large, the aperture will

not fully close and the reading will be inaccurate.

3-12

OPERATING INSTRUCTIONS

• A common mistake made when using clamp-on probes is

attempting to measure dual conductors carrying current in
opposite directions (e.g., - a lamp cord). Each conductor
produces a magnetic field, but the fields oppose one another
for a net magnetic field of zero. It is necessary to split the
conductor pair and make the measurement on one conductor
only.

• When the LO BAT annunciator appears, readings may not be

accurate. Either use an ac adaptor (see the Specifications
section for voltage ratings) or replace both batteries at the
same time. Replacing only one battery will not damage the
unit, but will reduce the normal life of the new battery.

GENERAL MAINTENANCE

• Use only isopropyl alcohol and a cotton swab to clean the

aperture area. Never use a sharp instrument or a stiff brush

to clean the aperture or damage will occur!

WARNING!

The probe is a precision instrument with no servicable parts
and no adjustment points. Under no circumstances attempt
to disassemble the probe!

• Gently clean the display and case with a soft, dry cloth (do

not use chemicals!).

• If the meter is to be idle for an extended period of time,

remove the batteries. Battery corrosion can damage the
meter.

3-13

OPERATING INSTRUCTIONS

3-14

Section 4

Warranty

Omega warrants each instrument of its manufacture to be free of defects in
material and workmanship. Our obligation under this warranty is limited to
servicing or adjusting any instrument returned to our factory for that purpose,
and to replace any defective parts thereof. This warranty covers instruments
which, within one year after delivery to the original purchaser, shall be returned
with transportation charges prepaid by the original purchaser, and which upon
examination shall disclose to the manufacturer’s satisfaction to be defective. If
it is determined that the defect has been caused by misuse or abnormal
conditions of operation, repairs will be billed at cost after submitting an estimate
to the purchaser.

Omega reserves the right to make changes in design at any time without
incurring any obligation to install same on units previously purchased.

THE ABOVE W ARRANTY IS EXPRESSLY IN LIEU OF ALL OTHER W ARRANTIES
EXPRESSED OR IMPLIED AND ALL OTHER OBLIGATIONS AND LIABILITIES ON THE
PART OF OMEGA, AND NO PERSON INCLUDING ANY DISTRIBUTOR, AGENT OR
REPRESENTATIVE OF OMEGA IS AUTHORIZED TO ASSUME FOR OMEGA ANY
LIABILITY ON ITS BEHALF OR ITS NAME, EXCEPT TO REFER THE PURCHASER TO
THIS W ARRANTY. THE ABOVE EXPRESS W ARRANTY IS THE ONLY WARRANTY
MADE BY OMEGA. OMEGA DOES NOT MAKE AND EXPRESSLY DISCLAIMS ANY
OTHER W ARRANTIES, EITHER EXPRESSED OR IMPLIED, INCLUDING WITHOUT
LIMITING THE FOREGOING, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR
A PARTICULAR PURPOSE OR ARISING BY STATUE OR OTHERWISE IN LAW OR
FROM A COURSE OF DEALING OR USAGE OR TRADE. THE EXPRESS W ARRANTY
STATED ABOVE IS MADE IN LIEU OF ALL LIABILITIES FOR DAMAGES, INCLUDING
BUT NOT LIMITED TO CONSEQUENTIAL DAMAGES, LOST PROFITS OR THE LIKE
ARISING OUT OF OR IN CONNECTION WITH THE SALE, DELIVERY, USE OR
PERFORMANCE OF THE GOODS. IN NO EVENT WILL OMEGA BE LIABLE FOR
SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES EVEN IF OMEGA HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

This warranty gives you specific legal rights, and you may also have other rights
that vary from state to state.

4-1