Amprobe AM-140-TRMS Operating Manual

USER'S
MANUAL

AM-140
AM-140 TRMS
AM-160
AM-160 TRMS

Digital
Multimeters

1

1) SAFETY

This manual contains information and warnings that must be followed for operating the
instrument safely and maintaining the instrument in a safe operating condition. If the
instrument is used in a manner not specified by the manufacturer, the protection
provided by the instrument may be impaired. The meter is intended for indoor use only.

The meter is protected by double insulation per EN61010-1 and IEC61010-1 2nd
Edition (2001) to CAT III 1000V & CAT IV 600V. The meter also meets UL3111-1
(1994)* and CSA C22.2 No. 1010-1-92* to CAT III 1000V.

AM-140 Terminals (to COM) ratings:

V : Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.
A / mAµA : Category III and Category IV* 500 Volts AC and 300 Volts DC.

AM-160 Terminals (to COM) ratings:

V / A : Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.
mAµA : Category III and Category IV* 600 Volts AC and 300 Volts DC.

*Category IV safety standard (for DMMs) was first released in IEC61010-1 2nd Edition
in year 2001, and was not adopted as an UL published standard at the time this
manual was written.

Per IEC61010-1 2nd Ed. (2001) Measurement Category

OVERVOLTAGE CATEGORY II

Equipment of OVERVOLTAGE CATEGORY II is energy-consuming equipment to be
supplied from the fixed installation.
Note – Examples include household, office, and laboratory appliances.

OVERVOLTAGE CATEGORY III

Equipment of OVERVOLTAGE CATEGORY III is equipment in fixed installations.
Note – Examples include switches in the fixed installation and some equipment for
industrial use with permanent connection to the fixed installation.

OVERVOLTAGE CATEGORY IV

Equipment of OVERVOLTAGE CATEGORY IV is for use at the origin of the
installation.
Note – Examples include electricity meters and primary over-current protection
equipment.

2

TERMS IN THIS MANUAL

WARNING identifies conditions and actions that could result in serious injury or even

death to the user.

CAUTION identifies conditions and actions that could cause damage or malfunction in

the instrument.

WARNING
To reduce the risk of fire or electric shock, do not expose this product to rain or moisture.
To avoid electrical shock hazard, observe the proper safety precautions when working
with voltages above 60 VDC or 30 VAC rms. These voltage levels pose a potential shock
hazard to the user. Do not touch test lead tips or the circuit being tested while power is
applied to the circuit being measured. Keep your fingers behind the finger guards of the
test leads during measurement. Inspect test leads, connectors, and probes for damaged
insulation or exposed metal before using the instrument. If any defects are found, replace
them immediately. Do not measure any current that exceeds the current rating of the
protection fuse. Do not attempt a current measurement to any circuit where the open
circuit voltage is above the protection fuse voltage rating. Suspected open circuit voltage
should be checked with voltage functions. Never attempt a voltage measurement with the

test lead inserted into the µA/mA or A input jack. Only replace the blown fuse with the
proper rating as specified in this manual.

CAUTION
Disconnect the test leads from the test points before changing functions. Always set the
instrument to the highest range and work downward for an unknown value when using
manual ranging mode.

INTERNATIONAL ELECTRICAL SYMBOLS

!

Caution ! Refer to the explanation in this Manual
Caution ! Risk of electric shock

Earth (Ground)

Double Insulation or Reinforced insulation

Fuse

AC--Alternating Current

DC--Direct Current

2) CENELEC Directives

The instruments conform to CENELEC Low-voltage directive 73/23/EEC and
Electromagnetic compatibility directive 89/336/EEC

3) PRODUCT DESCRIPTION

Panel Illustration

3

1) 5-4/5 digits 500000
counts LCD display

2) Push-buttons for
special functions &
features

3) Selector to turn the
Power On or Off and
Select a function

4) Input Jack for 10A (+)
(20A for 30sec) current,
and for T2 (-) function

5) Input Jack (+) for all
functions EXCEPT

current (

A, mA, A) and

µ

T2 functions

6) Common (Ground
reference) Input Jack (-)
for all functions EXCEPT
T2 function

7) Input Jack (+) for
milli-amp, micro-amp,
and T2 (+) functions

4

Average sensing RMS calibrated

RMS (Root-Mean-Square) is the term used to describe the effective or equivalent DC
value of an AC signal. Most digital multimeters use average sensing RMS calibrated
technique to measure RMS values of AC signals. This technique is to obtain the
average value by rectifying and filtering the AC signal. The average value is then
scaled upward (calibrated) to read the RMS value of a sine wave. In measuring pure
sinusoidal waveform, this technique is fast, accurate, and cost effective. In measuring
non-sinusoidal waveforms, however, significant errors can be introduced because of
different scaling factors relating average to RMS values.

AC True RMS

AC True RMS, normally refers as True RMS, identifies a DMM function that is AC
coupled, and responds accurately only to the effective RMS AC component value
regardless of the waveforms. However, DC component plays an important role in the
distorted non-symmetrical waveforms, and will also be of interest sometimes. A full
wave rectified sine waveform is a good example, and the AC true RMS function will
only give the AC component reading which is at 43.6% of the total effective DC+AC
RMS reading.

DC+AC True RMS
DC+AC True RMS calculates both of the AC and DC components given by the
expression

when making a measurement, and can respond
accurately to the total effective RMS value regardless of the waveform. Distorted
waveforms with the presence of DC components and harmonics may cause:

1) Overheated transformers, generators and motors to burn out faster than normal

2) Circuit breakers to trip prematurely

3) Fuses to blow

4) Neutrals to overheat due to the triplen harmonics present on the neutral

5) Bus bars and electrical panels to vibrate

AC Bandwidth

AC bandwidth of a DMM is the range of frequencies over which AC measurements can
be made within the specified accuracy. It is not the frequency measurement function,
and is the frequency response of the AC functions. A DMM cannot accurately measure
the AC value with frequency spectrums beyond the AC bandwidth of the DMM.
Therefore, wide AC bandwidth plays an important role in high performance DMM. In
reality, complex waveforms, noise and distorted waveforms contain much higher
frequency spectrum than its fundamental.

5

NMRR (Normal Mode Rejection Ratio)
NMRR is the DMM's ability to reject unwanted AC noise effect that can cause
inaccurate DC measurements. NMRR is typically specified in terms of dB (decibel).
This series has a NMRR specification of > 60dB at 50 and 60Hz, which is a good and
definite ability to reject the effect of AC noise when making DC measurements.

CMRR (Common Mode Rejection Ratio)

Common mode voltage is voltage present on both the COM and VOLTAGE input
terminals of a DMM, with respect to ground. CMRR is the DMM's ability to reject
common mode voltage effect that can cause digit rattle or offset in voltage
measurements. This series has a CMRR specifications of > 90dB at DC to 60Hz in
ACV function; and > 120dB at DC, 50 and 60Hz in DCV function. If neither NMRR nor
CMRR specification is specified, a DMM's performance will be uncertain.

Analog bar-graph

The analog bar graph provides a visual indication of measurement like a traditional
analog meter needle. It is excellent in detecting faulty contacts, identifying
potentiometer clicks, and indicating signal spikes during adjustments. Analog bar-graph
is not available in AC+DC True RMS Voltage & Current modes.

4) OPERATION
AC Voltage, DC Voltage, DC+AC Voltage, &

Hz Line Level Frequency

In AC Voltage, press SELECT button momentarily to toggle between AC and dBm. In
DC Voltage, press SELECT button momentarily to toggle between DC, and DC+AC. In
mV Voltage, press SELECT button momentarily to select DC, AC, or DC+AC. The new
settings will be saved automatically to the non-volatile memory as power up default. In
DCV and DCmV, press 500000 button momentarily to toggle between 4-4/5 digits and
5-4/5 digits readings. In voltage or current functions, press the

Hz push button
momentarily to activate or to exit Line Level Frequency measuring function. Line Level
Frequency measuring function is designed especially for noisy electrical high voltage
signals.

Note: In dBm function, power up default reference impedance will be displayed for 1
second before displaying the dBm readings. Press dBm-Ω (RANGE) button
momentary to select different reference impedance of 4, 8, 16, 32, 50, 75, 93, 110,
125, 135, 150, 200, 250, 300, 500, 600, 800, 900, 1000, up to 1200Ω. The new
impedance value will be saved automatically to the non-volatile memory as power up

default.