Using the EEDM504D DVOM

DVOM stands for: DIGITAL VOLT OHM METER

DVOM – DMM - Multimeter A DVOM can also be called a digital multi-meter DMM stands for: Digital Multi Meter The term Multimeter may also be used

Other functions Besides measuring volts and ohms most DVOMS can also measure : Amps Frequency Duty cycle Both AC and DC voltage and Amperage can be measured The EEDM504D DVOM in your toolset can also measure capacitance

Analog meters Analog meters display electrical measurements using semi-circular dials and needles Analog meters are not as accurate as DVOM and are harder to read Due to the low impedance of Analog meters some electronic circuits can be damaged if the meter is used incorrectly Analog meters are obsolete and rarely used in automotive diagnostic applications

Digital meters Digital meters display electrical measurements as numbers on a LCD screen Digital measurements are more accurate than analog and are much easier to read The high impedance of the meter makes it safe to use on delicate electronic circuits Features such as ‘Hold’ and ‘Min / Max’ are only available on digital type meters

All DVOMs are sold with a minimum of two test leads - one red and one black There is no electrical difference between the two color leads Test Leads The two colors help prevent confusion as to which lead is connected to the terminal sockets

Test leads The end of the lead is called a probe The tip of the probe is very sharp so that it can penetrate through any corrosion that may be present at the point in the circuit being tested

CATII Test Leads The test leads that come with the EEDM504D are CAT II certified for voltages up to 1000Vdc The EEDM504D meter with the supplied test leads should be safe for testing the high voltage electrical systems on hybrid and battery electric vehicles

CAT III rating The EEDM504D DVOM is rated as CAT III multimeter This means that the meter is safe to use in high voltage applications such as testing terminal voltage on the battery array of a hybrid vehicle The test leads used with the DVOM are rated CAT II The ISO symbol shown here means ‘Danger – High Voltage’ It serves as a reminder to the technician that there is the potential for electric shock when working with high voltage equipment

‘Banana’ plugs type jacks Most DVOMs use sheathed female ‘banana’ type plug sockets to connect the test leads to the meter This type of socket is found on most DVOM There are a wide variety of test leads and adapters that will plug right into the DVOM that can be purchased at parts stores or via the internet

Sheathed ‘Banana’ plugs The ends of the test leads that connect to the DVOM are called ‘banana’ plugs Sheathed banana plugs protect the technician from electric shock when working on high voltage systems Unsheathed banana plugs should only be used when working on low voltage system [normal automotive service] Unsheathed Sheathed

Probe tip sleeves The EEDM504D comes with protector sleeves screwed onto the probe tips The sleeve prevents accidental shocks from contact with the probe tip They can be removed when working on low voltage systems

Alligator clips Two booted alligator clip adapters are included with the meter The alligator clip adapters screw onto the threads at the probe tips

Alligator clip test leads Test leads with alligator clip ends are more useful – especially for the ground lead They can be easily clipped to a jumper wire or paper clip that is in contact with the electrical terminal They allow the technician to make measurements with one or both hands free … this is especially useful when it is necessary to goose the throttle or toggle a switch while observing voltage, current etc.

Homemade custom test leads Banana plugs can be purchased at Radio Shack or through the internet You can easily make your own custom test leads using wire and terminal ends scavenged from old electrical chords and junk found around the shop This ground clamp test lead was made from the power cord of an old 12 volt drop light

Modular test leads Modular test leads have a sheathed banana plug at both ends Different types of probes or clamps may be attached to the lead wire without removing the entire lead wire from the meter

Modular test leads A wide range of test lead ends are available through parts stores and the internet Insulation piercing adapter Large alligator clip Terminal back probe adapter Standard probe tip Wire end clamping adapter

Back probing electrical connectors Rubber gasket Nearly all the connectors on modern automotive electrical systems are sealed to prevent corrosion at the copper electrical connections Since there are no exposed places to make an electrical connection for testing a thin metal pin is inserted into the back side of the electrical connector until contact with the copper terminal is made

Back probing electrical terminals An inexpensive method of back probing is to insert a paper clip between the wire and rubber gasket that seals the electrical connector Filing or grinding down the end of the paper clip can make it easier to insert Back probing electrical terminals

Back probing electrical terminals Inexpensive back probe adapters are available for modular test leads that are faster and easier to use than paper clips

Meter Display Screen The EEDM504D uses a segmented LCD [liquid crystal] screen to display measurements When the DVOM is first turned on all segments will appear for about 3 seconds Each time you use the meter you should check to see if all segments are visable

Low Battery Warning If this symbol is displayed in the upper left corner of the display after the meter has gone through the 3 second LCD display check, the batteries are low and need to be replaced The meter uses two ‘AAA’ batteries Do not use NiMh rechargeable batteries – these batteries have a rapid self discharge rate and need charging every month A set of AAA batteries should last a year or more in normal use The batteries are accessible by loosening the three #1 Philips screws on the rear cover

Bar graph display The horizontal graph at the bottom of the display is used to graphically display electrical measurements When the digits on the display are changing rapidly it is impossible to make any sense of what is happening The back and forth movement of the graph makes it easy to see the upper and lower limits of the changes

Bar graph display Display Value = 40 As the value rises additional lines appear on the right side of the graph When the measured value exceeds 4xxx all of the lines except the first 4 will clear This allows the bar graph to display more data without being too difficult to read Display Value = 41

Auto – ranging turned on By default the meter is set to auto ranging Auto ranging automatically moves the decimal point and display values to the left or right to make the measured value as accurate as possible When the measured voltage changes from above 10 volts to a level less than 10 volts but more than 1 volt the decimal point moves one position to the left Auto ranging turned on

Auto – ranging turned off Auto-ranging is turned off by pushing the ‘Range’ button until the decimal point is in the desired location Auto ranging eliminates the leading zeros so that there is more room for less significant data to the right of the decimal point Auto ranging turned on

Returning back to Auto-Ranging mode Depress the ‘Range’ button for two seconds until ‘AUTO’ appears on the left side of the display Auto-ranging is not available in all test modes

Over Limit warning When the DVOM is set to manual ranging the letters ‘OL’ will appear on the screen if the unit measured is greater than the range currently selected Testing a voltage that exceeds the range will not damage the DVOM

APO Mode The APO [Auto Power Off] Mode powers down the display circuit when there has not been any activity for 15 minutes or more If you are monitoring a circuit for more than 15 minutes you can override the APA mode by pressing the REC button to set the meter to record mode The APO function is disabled in record mode Depress and hold the REC button for 3 seconds to exit the APO mode

APO resume When the DVOM turns itself off after 15 minutes you must turn the function selector to ‘Off’ and then back to any function to resume using the meter

REC mode [MIN / MAX] When in REC mode ‘APO’ is no longer displayed The REC mode lets you monitor maximum and minimum values over an extended period of time The REC mode can be used to monitor voltage, amperage and resistance Only MAX or MIN values can be viewed in REC mode – the current [live] value is not displayed

Battery #1 reference voltage The relative difference mode [Delta] is used when you want to no the difference between two measurements Delta mode Battery #1 reference voltage Connect the test leads to the circuit you want to measure then press the ‘REL’ button

Battery #1 reference voltage The value that was being measured when the ‘REL’ button was pressed is now held in the meters memory Delta mode The readings on the display are now the difference between the current measurement and the measurement held in memory Battery #2 Battery #1 reference voltage

Delta mode When the Delta symbol is displayed on the screen there is a value stored in memory The reading on the screen is the difference between the recorded value and the currently measured value The delta function can be used with voltage, amperage and resistance

Function selector knob The rotary function selector knob allows the technician to select the type of electrical measurement to be made

Function modifier buttons Additional buttons are arrayed below the LCD screen to change the display type, select alternative functions and to turn some features on and off

‘Com’ socket The black test lead is connected to the ‘COM’ socket for all test modes

‘Volt/Ohm /Hz’ socket The red test lead is connected to the ‘Volt/Ohm/Hz’ socket The red lead should be connected to this socket when measuring: Voltage Resistance [Ohms] Frequency [Hz] Diode test

10A Socket The red test lead is connected to the ‘10a’ socket when measuring amperage [without an amp clamp] Make sure you remove the red lead from the ‘10a’ socket after testing amps If the lead remains in the ‘10a’ socket when you try to measure volts the internal fuse will be blown and the meter may be damaged !!!!!

MilliAmp / MicroAmp Socket The socket labeled mAA is used when testing very low circuit amperage – less than .5 amps You will probably never use this function

Lead connections for voltage measurement For AC and DC voltage testing the black test lead is connected to the COM socket and red test lead is connected to the V socket

CAUTION! Do not attempt to make a voltage measurement if a test lead is plugged in the A or mAuA input jack Instrument damage and/or personal injury may result.

Measuring DC voltage Connect the black test lead to the ‘COM’ socket Connect the red test lead to the V socket Rotate the function selector knob to the DC voltage position

Function – DC Voltage When this function selector knob is turned to this symbol the meter is set to measure DC voltage DC [direct current] is found throughout the vehicles electrical system 95% of the time that you spend with your DVOM will probably be measuring DC voltage When the DC volt function is selected the meter will read the average voltage in a pulsed DC circuit

Measuring DC voltage Connect the voltmeter leads in parallel to the circuit being measured Fuse Light switch Negative Terminal The red lead is connected to the higher voltage The black lead is connected to the lower voltage

Absolute voltage measurement When the black test lead is connected to the battery negative terminal or to chassis ground all voltage measurements will be absolute voltages Light switch Negative Terminal Fuse

Voltage drop measurement Measuring the difference in voltage from one point in a circuit to another is called Voltage Drop measurement Measured voltage = 0.12 V Absolute voltage = 12.53 V Fuse Switch Positive Terminal Absolute voltage = 12.65 V The red lead is connected to the higher voltage The black lead is connected to the lower voltage

Black lead is connected to a good body ground Measuring Voltage In this illustration the electrical connector for the parking light bulb has been disconnected to determine if there is voltage at the connector Red lead is connected to the parking light power feed terminal

Voltage drop measurement Voltage drop measurement is used to find resistance in a circuit Voltage drop may be measured on both the power side and ground side of a circuit Measured voltage = 0.086 V Negative Terminal Absolute voltage = 0.86 V Fuse Switch Absolute voltage = 0.0 V If there is no resistance between two points in a circuit the voltage drop should be zero Ground Terminal

Voltage drop – ground side To measure resistance using a voltage drop test electrical power must be flowing through the circuit Red lead is connected harness connector ground pin Black lead is connected to body ground In this test the parking light is connected to the harness terminal and the lights have been turned on The red lead is connected to the circuit by ‘back probing the terminal’

The best way to determine if the battery is fully charged is to measure battery voltage when the ignition is turned off Turn on the headlights for 30 seconds and then turn them off Connect the black lead to the battery negative terminal and the red lead to the positive terminal Measuring Battery SOC

Battery State of Charge At 70 F 100% - 12.60 volts or more 75 -100% - 12.4 – 12.6 volts 50 - 75% - 12.2 – 12.4 volts 25 - 50% - 12.0 – 12.2 volts 0 - 25% - 11.7 – 12.0 volts Completely Discharged < 11.7 volts

Reversed test lead polarity If the test leads are accidentally reversed – so that the black lead [COM] is connected to the higher voltage and the red lead is connected to the lower voltage no damage will occur. The meter will read normally except that there will be a negative sign to the left of the voltage display Negative Terminal

Pulsed DC voltage On Off When the DC volt function is selected the meter will read the average voltage in a pulsed DC circuit Modern electronic controls normally control the speed of small electric motors and the intensity of lights by turning the circuit on and off hundreds of times each second

50% Duty Cycle 5 milliseconds [mS] 12 volts 0 volts 5 mS In the circuit shown here the current is turned on and off 100 times each second If the circuit is turned on for 50% of the time and off for the remainder, the DVOM will measure 6 volts

10% Duty Cycle 1 mS 12 volts 0 volts 9 mS If the current is turned on for 10% of the time and is off for the remaining 90% the DVOM will measure 1.2 volts

Hold function Hold Indicator Pressing the ‘HOLD’ button will freeze the screen display The feature is handy when you are performing a test where you need measure voltage while to looking at something else Pressing the ‘HOLD’ button a second time returns the meter to normal operation

Function - Millivolts When millivolts function is selected you will need to select AC or DC using the function modifier button Press the AC/DC button until the desired current type is displayed on the LCD

Millivolts display screen Millivolt indicator Current type Auto ranging is turned on The screen shown here indicates a measurement of 1237 millivolts or 1.237 volts Note: since the reading is above 1000 mV there is no decimal point displayed

Importance of the decimal point 1.237 volts The only difference between these two display screens is the decimal point between the first two digits The display at the top shows 1000 times more voltage than the bottom display 0.001237 volts

Function – AC Voltage When this function selector knob is turned to this symbol the meter is set to measure AC voltage AC [Alternating current] is found in ABS wheel speed sensors, crankshaft position sensors and vehicle speed sensors [VSS]

Measuring AC Voltage You can check the AC voltage calibration of your meter by inserting the probes into the female terminals of an extension cord Insert the test leads with the extension cord disconnected

Measuring AC Voltage Set the meter for AC voltage then plug the extension cord into a wall socket The meter should read about 120 Vac

Measuring AC voltage The most common use for AC voltage measurement is in testing the output of ABS wheel speed sensors Since there is no positive or negative terminal in AC current it doesn’t matter which lead gets connected to the sensor terminals Manually spin the tire while observing voltage Since the voltage increases as tire speed increases auto ranging should be turned off Wheel speed sensor

Connecting to sensor The most common junction point for the wheel speeds sensors at the wheel hub Back probe adapters Some wheel speed sensors have long pigtail leads that join the vehicle’s wiring harness inside the cabin

Testing ABS Wheel speed sensor voltage Set the meter to read AC volts Spin the tire by hand Normal voltage when the wheel is spun by hand is less than on Volt AC The ABS wheel speed sensor generates its own voltage – the faster it spins the higher the generated voltage

Function - Resistance -  When the resistance function is selected as small amount of current is sent from the DVOM through the circuit being tested The DVOM measures the amount of amperage that passes through the circuit, calculates the amount of resistance and displays the value in ohms on the LCD screen

 Function – lead test The red lead is connected to the V socket and the black lead is connected to the COM socket Connect the red and black test probes and check to make sure the meter reads .2 or less

Function - Resistance -  Resistance testing is often used when bench testing magnetic coils in relays, solenoids, ignition coils and electric motors When measuring resistance there is no AC or DC mode to setup …. resistance is the same no matter what type of current normally flows through the circuit When measuring resistance in circuits on the car the circuit must be powered down and disconnected from the rest of the electrical system

Fuel level sending unit Measuring Resistance Resistance [Ohms] is measured with the circuit or component unpowered and electrically disconnected from the rest of the vehicle’s electrical system Fuel level sending unit Float Fuel pump

Testing ABS wheel speed sensor resistance When testing the output voltage and frequency of ABS wheel speed sensor test the resistance of the coil winding to insure that you have a good connection between the DVOM and the sensor Normal resistance is typically between 800 and 1200  1.097 k Function selector set to  Note: Do not spin the tire when DVOM is in  mode

OL warning in  function Infinite resistance is displayed on the DVOM with the letters ‘OL’ OL stands for ‘Over Limit’ but it does not mean anything bad will happen If OL is displayed when measuring resistance it means there is no complete electrical path for current to flow through the circuit between the two test leads – the circuit is ‘Open’ This condition is also called no continuity

Audible continuity test Turning on the audible continuity test buzzer allows you to test for opens [broken circuit] between two points in the circuit without having to look at the meter When this function is activated the buzzer will sound if there is a closed electrical path between the two test leads

Audible continuity test Audible continuity test indicator The circuit cannot be powered and should be disconnected from the rest of the electrical system to prevent current flowing through other electrical components …. giving the test a false positive result The circuit resistance needs to be less than a few ohms to activate the buzzer

Diode Test Use the diode/buzzer button to toggle the meter between  measurement, diode test and continuity [buzzer] test modes

Diodes Diodes are one way valves for electrical current Diode Symbol Diodes are found inside relays and solenoids and are sometimes found in the fuse box Diodes prevent damage to sensitive electronic components from voltage spikes when electromagnets are turned off Diodes are also found in rectifiers – devices that convert AC current into DC There are 6 diodes mounted on a heat sink inside every alternator

Diode test function indicator In the diode test mode the meter sends a very low voltage through the test leads – less than 1/10th of a volt If no current flow is detected the meter increases the voltage until a small amount of current flow is detected The meter reads the voltage that is required to turn on [forward bias] the diode

Diode test – forward biased When the diode is forward biased the voltage reading will be very low About .3 volts for germanium diodes About .6 volts for silicon diodes Black band

Diode test - reverse biased When the position of the leads is reversed the diode should not conduct any electric current When the meter reaches peak voltage [about 3 volts] and there is no flow of electricity through the diode the reading displayed will be ‘OL’ Black band

Measuring current Select Amps AC/DC to measure current The AC/DC function modifier button is used to toggle between AC and DC current The maximum amount of current that the EEDM504D can measure is 10 Amps If the meter is connected to a circuit carrying more than 10 Amps the fuse will blow and the meter can be damaged !!

Measuring current Connect the Red lead to the ‘A’ socket on the far left Connect the Black lead to the ‘COM’ socket

Wiring harness connector Measuring DC current When measuring DC current the meter is connected in Series with the circuit being tested Fuel pump relay Fuse Wiring harness connector Fuel pump Jumper wire Note: This test should be performed with the fuel pump in the car. Never power up a fuel pump that is outside the fuel tank

Measuring DC current Since the amount of current flowing through a circuit with only one load is the same at every point in the circuit a simpler method of testing current is to connect the DVOM across the fuse terminals in the fuse box Fuel pump relay Wiring harness Fuse socket Fuel pump Note: This test should be performed with the fuel pump in the car. Never power up a fuel pump that is outside the fuel tank

Measuring parasitic draw Parasitic draw is the amount of current flowing from the battery to the electrical system when the ignition key is turned off Disconnect the negative battery cable Connect the black probe to the battery neg post and the red probe to the battery ground cable Normally there is less than ½ amp used by the computer system’s standby and memory functions

Measuring parasitic draw With the ignition turned off and the doors closed disconnect the battery negative cable Connect the black lead to the negative battery post and the red lead to the battery negative [ground] cable Function selector set on AMPS

Measuring parasitic draw Open the drivers door and the meter should jump to ½ amp or more This additional amperage is current draw of the interior lights Black lead connected to battery negative post Red lead connected to ground cable

Isolating excess parasitic draw If there is excessive parasitic draw the battery may completely discharge overnight Removing fuses and measuring the draw on each circuit can isolate the source of the drain

Measuring current at the fuse socket Remove the fuse using the fuse puller [located inside fuse box]

Measuring current at the fuse socket A fuse socket jumper makes it easy to connect the DVOM to the fuse terminals in the fuse box

Standard automotive terminal width and spacing Fuse socket jumper Inexpensive fuse jumpers are available for different size fuse sockets that allow you to connect you DVOM the fused circuit The top of the jumper has ¼” male spade terminals that allow you to build custom test leads using crimped wire terminal ends ¼” spade Standard automotive terminal width and spacing

Ammeter check Before using the DVOM to measure DC amps you may want to check the operation of the meter and 10A ammeter fuse Connect the DVOM and your test light in series with the battery The test light should light up and the meter should read ¼ to ½ amp

Ammeter check Red lead connected to positive battery terminal Black lead connected to test light probe tip Test light alligator clip connected to negative batter terminal If the test light illuminates and the ammeter reads about ¼ to ½ amp the fuse in the DVOM is good and the meter is working properly

Measuring frequency When the function selector is set to Hz the meter will measure frequency The unit of measure is in Hertz [Hz] The term Cycles Per Second [CPS] may also be used Frequency is normally associated with AC current but is also used in measuring pulsed DC current

Measuring frequency Frequency measurement is done mostly on speed sensors The sensor most often tested is the ABS wheel speed sensor Measuring frequency is a better test of the wheel speed sensor than measuring AC voltage

Measuring frequency Connected the test leads to the sensor terminals – it doesn’t make any difference which wire is connected to red and which wire gets connected to black The test leads are connected to the ‘COM’ and V sockets on the DVOM Rotate the tire by hand The faster you spin the tire – the higher the frequency

Measuring duty cycle On Off Solenoids valves that control the flow of liquids and vapor are throttled electronically by pulse width modulation The electric current controlling the solenoid is turned on and of many times each second The portion of time that the solenoid is turned on is called ‘duty cycle’

Duty cycle Connect the black lead to ‘COM’ and the Red lead to VHz Turn the function knob to select Hz Press Hz/Duty until ‘%’ is displayed

Duty cycle The range of duty cycle is from 0.1% to 99.9% Normally what you are looking for is the duty cycle measurement to change rapidly as the engine or transmission responds to changes in the operating conditions

Measuring capacitance There is not much use for capacitance testing on modern automobiles You can use the function to test the condenser on a very old car that has ignition points The condenser must be disconnected from the ignition system The condenser here measures 369.3 nano-Farads

Accessories You can purchase accessories that expand the DVOMs testing abilities: High amperage inductive current probes allow you to measure electrical current up to 1000 amps without disconnecting any wires Temperature probes are helpful in diagnosing heating and air conditioning problems and can be useful in troubleshooting engine performance problems Pressure transducers allow you to measure hydraulic pressure in automatic transmissions while driving the vehicle

Inductive Amps Clamp The inductive amps clamp measures the strength of the magnetic field surrounding a conductor The circuitry inside the amps produces a voltage signal that is directly proportional to the amount of current passing through the conductor The amps clamp plugs directly into the ‘COM’ and ‘VHz’ input jacks

Amps Clamp The amps clamp is powered by a 9 volt battery A Hall-effect sensor detects the magnetic field and produces one millivolt for each ampere of current passing through the conductor The clamp must be zeroed before each use to compensate for the decrease in voltage as the 9V battery discharges

Inductive Amps Clamp To use the amps clamp set the DVOM to mV DC Set the range so that the decimal point is one place from the right Turn the zero adjust wheel until the meter reads 000.0 Wrap the clamp around the conductor wire to be measured Turn on the circuit and record the measurement

Measuring Amps with the Amp Clamp When wrapping the amps clamp around a wire make sure to separate the wires so that only the conductor being measured is within the clamp jaws

Incorrect Amps clamp setup If the jaws of the amps clamp surround both the power and ground wires the magnetic fields surrounding the two wires are phased in opposite directions The two magnetic fields will cancel each other out No matter how many amps pass through the circuit the meter will read zero

Polarity arrow The amps clamp should be positioned so the polarity arrow on the clamp faces the direction of current flow If the clamp is positioned in the opposite direction a negative sign will be displayed to the left of the amperage measurement

Meter maintenance The batteries and fuses are accessible by loosening the three #1 Philips screws on the rear cover

Batteries The EEDM504D uses two AAA batteries to power the measurement, logic, display, diode test and resistance testing circuitry When the battery voltage approaches the limit of its ability to power the meter the ‘battery’ symbol on the display will appear

Fuses The EEDM504D has two fuses 10 amp for 10A ammeter circuit 500 milliAmp for the milli/micro ammeter circuit

Testing internal fuses To check the condition of the 10A internal fuse without removing the rear cover Set the DVOM to Diode test mode Connect the red lead to the VKz jack Touch the red test lead probe to the A input jack – make sure to touch the metal contact inside the socket If the meter reads anything other than OL the fuse is good If the meter reads OL the fuse is blown Repeat the test on the mA input socket to test the 500 mA fuse

Replacement fuses Replacement fuses EEDM5O4B1 10A 600 volt ceramic EEDM504B2 500 mA 600 volt ceramic Snap-On part numbers Warning!!! …. if 250 volt fuses are substituted for the 600 volt fuses specified by the manufacturer the meter is no longer safe to operate on high voltage systems

Cleaning Do not clean the meter case or display screen with anything other than a damp cloth and a few drops of mild soap Strong solvents like Brakeklean or carburetor cleaner can damage the plastic case and LCD screen