Transcript basics_of_dmm-utilit..

Basics of Digital Meters
Utility Applications
© 2007 Ideal Industries
www.idealindustries.com
Basics of Digital Meters- Utility Applications
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Understanding the basics
• Basic Electricity
•
•
•
•
Safety
Analog or Digital
Manual or Auto-ranging
Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Basic Electricity
• Fluid Dynamics
– How water flows
• Electrical Theory
– How electricity flows
• Types of Sources
– AC vs. DC
– Measuring AC
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Fluid Dynamics to Electrical
Theory
How water flows
• Water Pressure
• Voltage (V)
– Pressure created by a pump
or stored in towers
• Flow or Current
– The amount of water
flowing through a pipe
– Pressure applied to the
conductor
• Amperes or Amp (I or A)
– Flow of electrons in the
conductor
• Impedance
–
• Impedance or resistance
Anything that impedes the
()
flow of current
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– Impedes or resist the flow of
electrons
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AC Source
• Alternating Current (AC)
– Most common
– Produced by a generator
– Has a positive and
negative component
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DC Source
• Direct Current (DC)
– Stored energy or
derived from AC with
electronic rectifier
– Positive component
only
– Used to power
electronic devices
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Understanding the Basics
• Basic Electricity
• Safety
• Analog or Digital
• Manual or Auto-ranging
• Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Why should we be
Concerned?
• An electrician
troubleshooting a live
480V motor control center
receives serious secondand third-degree burns
from an electric arc. The
cause?
– Meter was incorrectly
switched to resistance on
his multimeter instead of
voltage.
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Why should we be
Concerned?
• Two electricians are severely
burned — one fatally — while
testing for voltage in a motor
starter. One held the multimeter
while the other applied the
meter's probes to energized
terminals. One electrician's
movement caused one test lead
banana plug (energized from the
circuit under test) to pull loose
from the multimeter jack.
– The plug made contact with
the starter's grounded metal
enclosure and initiated a
high-energy arc.
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Common Mistakes Made
• Test Leads in the Current
input ports and user
mistakenly makes an AC
or DC Voltage
– In this example there were
two errors made by the end
user.
• AC voltage measurement
with the Test leads in the
current input.
• Improper fuse had been
used in the meter from a
past error.
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Common Mistakes Made
Current
If Voltage is measured, Leads in Current input
Protection
Fuse
• Here is what happens.
– If the unit is not fused it can lead
to damage of meter or to the
operator
– Current inputs are very low
resistance. Most current inputs
are less that 1 Ω. This is like
applying a short to the line.
– For current input protection
most DMMs’ are Fused.
– The better ones use high energy
fusing.
Ideal 61-490 series gives a probe
error message and High audible
warning if this mistake to made
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Common Mistakes Made
• Function Switch in wrong
function for attempted
measurement
– Most common is AC or DC
voltage measurement with meter
in the Ohms function
– Most IDEAL meters are Overload
Protected and the protected levels
are listed in the operation
manual.
Ideal 61-700, 61-760 and 61-770 series will
give you a Hi-V light and audible warning if
you make this Mistake
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Common Mistakes Made
• Using a meter in an area
above its stated rating
– Example: 2,300 voltage
measurement with an
instrument rated for Low
Voltage (600V AC/DC.)
– Overload Protected can not
protect you from this Kind
of mistake.
– Most Overload protected is
rated based on instruments
highest voltage
measurement rating.
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There are Bold Electricians and
Old electricians, but not many
Bold-Old ones
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Common Safety Hazards
• Electrical Shock from
accidental contact from
live electrical circuits or
devices
– Use double insulated rated
leads
– Shrouded input jacks with
finger guards
– Test for proper continuity
often.
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Common Safety Hazards
• High Voltage transients
from lightning, large
inductive loads being
switched on and off, or
capacitive discharge.
– Select meter with the proper
UL/IEC Category rating for
the environment that user is
going to be working in.
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Certified Devices and
Equipment
• Look for tools that are
Certificated by an independent
lab,
– UL , IEC, CSA.
• Pay close attention to the safety
rating on the equipment.
– Never use equipment that is not
properly rated, Check Sp
IEC Cat ratings
• Never use accessories that are not The New UL 61010 standard
recommended or rated for your incorporates features of the IEC
601010 standard. This standard has
tester or environment.
improved safety benefits over the old
UL 1244 standard
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IEC Category Ratings
• If a lighting strike was to hit your
electrical service a certain amount
of energy or impulse would travel
and be dissipated by the electrical
service.
The closer to the source of the
impulse the Higher available fault
current.
• IEC 61010 defines as four
Categories:
– CAT IV “Origin of
installation”,
– CAT III Distribution Level,
– CAT II Local level,
– CAT I Signal Level,
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Safety Practices
• Visually inspect the
test tool.
– Check for any contaminate on the test
leads, tester case, holsters, and
accessories.
– Never use testers that have signs of
cracked cases, or loose components.
– Never use a tester in an environment
that is beyond the capabilities
described in the specifications
– Use manufactures recommended
replacement components, like leads
and fuses.
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Safety Practices
• Visually inspect Test
Leads
–
–
–
–
–
Proper Category rating
Double insulation
Shrouded connectors
Finger guards
Insulation not damaged: not melted,
cut, cracked, stretched
– Connectors: no insulation pulled away
from end connectors
– Probe tips: not loose or broken off (too
short)
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Before you get Started
• Whenever possible, work on de-energized circuits.
• Use well maintained tools and appropriate safety gear
• Safety glasses, insulated tools, insulating gloves,
flash suits, insulating mats, etc.
• Follow proper safety precautions and Lockout /Tag out practices.
• Never Work alone when making measurements on live circuits.
• Always do a performance test on your tester before making a
measurement on an unknown circuit.
– Use the 3 point method. Measure a known test point , Make the unknown
measurement, then back to the known test measurement.
– Change battery when indicated
– Check test leads regularly
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Before you get Started
• Quick Check of your Test Tool
–
–
–
–
•
Digital Multimeter or Digital Clamp meter
Check the Test Leads
Place the DMM in the lowest resistance range and short the Test Leads
Move the test lead at in input of the meter at the ankle of the leads. Watch that the
resistance is less than 0.5 ohms. Do the same at the leads grip and tips. If at any
time during this test the resistance exceeds 0.5 ohms the leads my need to be
replaced.
It is also a good Idea to check the DC voltage and Ac voltage with a known
source before beginning the day.
– This doesn't negate the “Three point measurement” method.
•
•
If the unit has current, check the Fuse, and remember to replace with only the
manufacturer recommended replacement part.
Remember to always be aware of your battery usage. Digital instruments will
become erratic or can give improper readings once the power drops below
normal operating levels
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Know your tester
•
•
•
•
Packaging
– Material,
• Insulation rating
• Environmental rating,
Splash proof or not.
Features
– MIN/MAX, Peak, Hold
Measurement Functions
– AC Volts, DC Volts
Capacitance, etc
– Measurement range and
Maximum input
– Input protection.
Safety
– CATegory rating, UL, CE
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Electrical Testers
• Analog solenoid Testers
– Very low input impedance
– AC Voltage
– Continuity testing on some
models
– Low Accuracy and resolution
• Digital Testers
–
–
–
–
Low input impedance
AC or DC Voltage
Continuity testing
Good Accuracy and Resolution
• Added Features
– NCV (Non-contact Voltage
– Current
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Digital Multimeter and
ClampMeter
• Multimeter
– Full Voltage ranges
– Full Resistance ranges
– Low current measurement
through internal shunts
• ClampMeter
– One or two Voltage ranges
– Limited Resistance ranges
– High Current through the
fixed jaw (current
transformer)
The IDEAL TightSight™
ClampMeter is also a Full
functional Digital
Multimeter
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Understanding the Testers
• Basic Electricity
• Safety
• Analog or Digital
• Manual or Auto-ranging
• Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Function Switch
• Most DMMs have rotary dial to change test
functions.
• Manual ranging DMMs
– Require manual setting of the range
• Lower cost
• Forces you to “think” before testing
• Faster response time
• Auto Ranging DMMs
– Automatically chooses the range
• Simpler to use
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Understanding the Testers
•
•
•
•
Basic Electricity
Safety
Analog or Digital
Manual or Auto-ranging
• Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Display Count
Typical displays are 2000
or 4000 counts”
–Ranges
on the dial are in
series of 2’s or 4’s
–No
Function information is
displayed.
Auto ranging meters will
have function symbol
– They are also visible on
the LCD Display
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Range and Resolution
• Range determines
– The maximum reading
– The number of decimal places
displayed
• Resolution determines how
many digits after the decimal
point
– Higher resolution = more
decimal places displayed
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200V on the 600V Range
1V Resolution
200V on the 400V Range
0.1V Resolution
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Range and Resolution
If we measure a
240V supply with
a 2000 count
Meter we would
be on the 600V
range and read
240V
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Range
600
200
20
2
200m
Reading
600
199.9
19.99
1.999
199.9
Basics of Digital Meters- Utility Applications
Resolution
1
.1
.01
.001
.1mV
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Range and Resolution
Measure the same
240V supply with a
4000 count Meter
you will be on the
400 Range and have
one more digit of
resolution 240.0V
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Range
600
400
40
4
400m
Reading
600
399.9
39.99
3.999
399.9
Basics of Digital Meters- Utility Applications
Resolution
1
.1
.01
.001
.1mV
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Measurement Functions
V
AC Voltage
Measures amount of AC
Electrical pressure
V
DC Voltage
Measures amount of DC
Electrical pressure
mV
Milli Volts
.001V or 1/1,000 V
A
Amperes
mA
Milli Amperes
µA
Micro Amperes
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Measures amount of
electron flow
.001A or 1/1,000 A
.000001A or 1/1,000,000A
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Measurement Functions

))))
Ohms
Measure of the resistance to
electron flow
Diode
Device used to control direction
of electron flow
Audible Continuity Audible indication of
continuity
HZ
°F
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Capacitance
Device used to store electrical
potential
Hertz
Measurement of Frequency or
number of cycles per/sec
Degrees Fahrenheit Temperature Measurement
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Measuring AC
• Average responding meters take
a single sample to measure the
waveform.
– Only accurate where a clean 60Hz
sine wave exists
• True RMS meters take several sample
to improve accuracy of measurement
– Found in commercial and
industrial environments
– Caused by electronic lighting,
computers Equipment and Industrial
electronic control loads
– NEC recommends True RMS meters for
testing all electrical power systems
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Numerical System
Term
Numerical value
Term
Numerical value
Giga
1,000,000,000
Milli
.001
Mega
1,000,000
Micro
.000001
kilo
1,000
Nano
.000000001
Term
giga mega kilo Base milli micro nano
Symbols
Expressio
n
G
M
k
m
m
n
6
3
-3
-6
X10
X10
X10
X10
X10
X10
X10
9
9
0
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Understanding the Testers
•
•
•
•
•
Basic Electricity
Safety
Analog or Digital
Manual or Auto-ranging
Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Break
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Understanding the Testers
•
•
•
•
•
Basic Electricity
Safety
Analog or Digital
Manual or Auto-ranging
Displays
– Range and Resolution
– Icon Symbols
– Numerical System
• Basic Measurement
– DC Volts& AC Volts
– Resistance, Capacitance
– Current
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Primary DMM Test Functions
• Voltage (V) - measured in volts
– Pressure created by a power supply
• Current (A) - measured in amps
– The amount of electricity flowing
through a conductor
• Resistance () - measured in ohms
– Anything that impedes the flow of
current
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Taking Measurements
•
•
•
•
•
•
•
•
AC Voltage
DC Voltage
AC Current
DC Current
Resistance
Continuity
Capacitance
Frequency
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IDEAL Test Board
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The Port Panel
• Black lead always placed
in Common Port (COM)
• Red lead is placed in Red
Port for the function to be
measured
• For Voltage connect to the
– ( VΩHz) Port
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DC Voltage Measurement
• DC Voltage Measurement
• Connect the leads to the
VΩHz and COM inputs
• Select VDC or
– If manual ranging select
proper range
• For 9V, Select the 20V
range
• Measure the 9 Volt battery
– If connected to the test
board look for ( +●
Battery● -) test points.
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Parallel Circuit
• In a parallel circuit,
Voltage is applied
equally to each load
connected to the circuit
– This is how our
receptacles in our homes
wired.the value
Ifare
I change
of the resistor in this
circuit will it change
the voltage across the
light???
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AC Voltage Measurements
• AC Voltage Measurement
• Connect leads to the
VΩHz and COM inputs
• Select VAC or
– If manual ranging select
proper range
• For 120V, Select the 200V
Range
• Measure receptacle, or
using test points on a line
splitter
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Never make a Voltage measurement with
the leads of the meter in the current input
ports
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Single Phase 3 Wire Meter
(Common Residential)
Class 100/200 (100/200 Amp)
4 Terminal, 240 Volt
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Single Phase 3 Wire Meter
(Common Residential)
Class 100/200 (100/200 Amp)
4 Terminal, 240 Volt
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Single Phase 3 Wire Meter
(Common Residential)
Class 100/200 (100/200 Amp)
4 Terminal, 240 Volt
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Average vs. True RMS
• True RMS responding
– The Meter calculates
the true effective
(heating) value of the
waveform.
– Average sensing
meters will not
correctly display the
effective (heating)
value on a “nonsinusoidal waveform.
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True RMS
• Measures the area under
the sine wave using a root
mean square calculation
• Gives an accurate AC
measurement when
harmonics are present
• NEC recommends True
RMS meters for testing
all electrical power
systems
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Current Measurements
ClampMeter or Clamp Adapter
• AC Current
–
–
–
–
–
Measures the magnetic field around a wire
Converts measurement to an amp reading
Only a single conductor can be tested
Magnetic fields of hot and neutral cancel out
Requires a line splitter in power cords
• DC Current
– DC current is measured using a Hall Effect
• An electronic device which measure the EMI of
AC and DC current.
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Test & Measurement
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AC Current Measurement
• AC Current Measurement
– Must be made on a single
conductor.
• Plug hairdryer into line
splitter
• Plug line splitter into
receptacle
• Clamp jaws around line
splitter
• Measure the current draw of
the hairdryer
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Series Current Measurement
• In a series circuit, loads within
the circuit have an effect on
the flow of electricity to the
other devices or loads
If I increase the value of the
resistor will it effect the brightness
of light.??
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Current Measurements
Series Method
• Requires an open circuit
– electrician must interrupt power
– Best to us a meter with fused inputs for safety.
• 1 to 10A Max on most DMM’s
• Primarily used to measure small Currents
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DC Current Measurement
4-20mA Control Loop
DC current measurement of a 4
to 20mA control loop
• A break must be made between
the transmitter and Controller.
• Place the Test leads in the
proper input ports. And select
DC mA
– 4 mA typically corresponds to
zero
– 20 mA typically corresponds to
Full scale.
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Continuity Measurement
• Continuity measurement
• Connect the leads to the
VΩHz and COM input
port
• Select the continuity
function
– Touch leads together
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“OL”
Customer breaker(s)
open
“Numerical
Value”
Breaker(s) closed
“0.0 to 0.8”
SHORT
on customer wiring
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Resistance Measurement
• Resistance Measurement
• Connect the leads to the
VΩHz and COM input
port
• Select the Ω ohms
Function.
– If manual ranging select
proper range
• Measure the Resistor on
the Test Board
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“OL”
Customer breaker(s) open
“Numerical
Value”
Breaker(s) closed
“0.0 to 0.8”
SHORT on customer wiring
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“OL”
Customer breaker(s) open
“Numerical
Value”
Breaker(s) closed
“0.0 to 0.8”
SHORT on customer wiring
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Diode Measurement
• Diode measurement
• Connect the leads to
the VΩHz and COM
input port
• Select the diode function
– Place Red lead on + and black
lead on – for “Forward bias”
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Capacitance
• Function used in testing
capacitors
– Storage devices that give
motors an initial energy
boost
• Capacitance is the ability
of a capacitor to hold its
charge
• Measured in
microfarads (MFD)
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Capacitance Measurement
• Capacitance Measurement
• Connect the leads to the
proper input posts
– On some units this isn’t the
Volt/Ohms port
• Select the Capacitance
Function
, MFD or mF
• Measure the capacitor on
the PC board
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Basic Advanced Features
• Basic of Advance
features found on most
high end DMM’s and
ClampMeters
– Hold or Data Hold
– Peak Hold
• Peak Min/Max
– Min/Max
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Measurement Functions
• Functions button
operation
– Primary Function
MIN/MAX press for 1
Second
– Press MIN/MAX To
cycle through Max/Min.
• Note display
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Measurement Functions
• To exit a Function
– Primacy Function
• Press for 1 second toggles
function A”ON”
• Press and hold for 2
seconds toggles function
“OFF”
– Secondary Function
• Press and hold for >2
seconds toggles function
“ON” or “OFF”
• Note display
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Hold Measurement Functions
• Hold or data hold is
used to lock the
current measurement
reading on the display
– While making a
measurement, press the
Hold button. Remove
test leads and observe
the displayed reading.
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Measurement Functions
• Peak Hold Records the
Maximum amplitude of a
voltage waveform.
• Peak min/max Records
the maximum and
minimum amplitude of a
voltage waveform.
Peak = RMS x 1.414
Example: 169.68= 120V x 1.414
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Min/Max Measurement
Functions
• Min/Max Records the minimum and maximum value
of a measurement. Each time a new min/max level is
achieved the new value will be recorded .
– Some DMM will also indicate new recorded values by an
audible beep.
This Function is
not fast enough to
capture Power
Quality Voltage
Event.
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Voltage Performance
Monitor
Key Points for comparison
•
High speed Even capture
•
Only important events are logged
•
Events are sorted by Time (log)
•
Events are sorted by Type (event)
•
Waveform shape is measured for THD
© 2007 Ideal Industries
www.idealindustries.com
Basics of Digital Meters- Utility Applications
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Clamp-On Ground Resistance
Test
• Advantage is that the
ground electrode doesn’t
need to be disconnected
from the electrical
system.
• The jaws of the clamp
must be placed in the
electrical path of the
systems grounding wire
to the ground rod
© 2007 Ideal Industries
www.idealindustries.com
Basics of Digital Meters- Utility Applications
69 of 69