Basic Instrumentation And Measurement - Function Generator

The Function Generator series are stable low distortion instruments, which generate signals in the frequency range up to 5MHz. Typical applications include a wide range of audio response testing application, vibration testing, servo system evaluation, ultra sound application and etc.

These instruments include the following features: logarithmic and linear sweep capabilities, together with a built in frequency counter. The sweep capability simplifies the task of finding resonant points of speakers, filter networks and other networks/structures. An oscilloscope may be connected to this instrument for the response to be displayed. The counter can be switched to measure and display the frequency of an external signal up to 150MHz.

Panel Control And Indicator

Front Panel

Rear Panel

FUNCTION DESCRIPTION

FRONT PANEL

1. Power Switch : Connect the AC power, then press power switch.
2. a) Gate Time Indicator : Press the power switch, Gate time indicator will start to flash (the gate of internal counter is 0.01 second)

2.   b) Gate Time Selector : Press the key to change gate time when use external           counter mode. The change order is according to 0.01s, 0.1s, 1s, 10s cycle by            pressing these keys.

3. Over Indicator : In the external counter mode, the indicator is illuminated when the output frequency is greater than the range selected.
4. Counter Display : Shows the external frequency by 6 x 0.3” green display, and shows the internal frequency by 5 x 0.3 green display.
5. Frequency Indicator : Indicate the current frequency value.
6. Gate Time Indicator : Indicate the current Gate time (external, counter mode use only)
7. Frequency Range Selector : To select the required frequency range by pressing the relevant push button on the panel as shown in Table 1 and Table 2.

Table 1 (for GFG-8215A/8216A/8217A/8219A)

Push bottom	1	10	100	1k	10k	100k	1M
Frequency Range	0.3Hz / 3Hz	3Hz / 30Hz	30Hz / 300Hz	300Hz / 3kHz	3kHz / 30kHz	30kHz / 300kHz	300kHz / 3MHz

 

Table 2 (for GFG-8250A/8255A)

Push bottom	1	10	100	1k	10k	100k	1M
Frequency Range	0.5Hz / 5Hz	5Hz / 50Hz	50Hz / 500Hz	500Hz / 5kHz	5kHz / 50kHz	50kHz / 500kHz	500kHz / 5MHz

 

8. Function Selector : Press one of the three push buttons to select the desired output waveform.
9. Duty Function : Pull out and rotate the knob to adjust the duty cycle of the waveform.
10. TTL/CMOS Selector : When push in the knob. The BNC terminal of (20) will output a TTL compatible waveform. If pull out and rotate the knob can adjust the CMOS compatible output (5-15 Vpp) from the output of BNC (20)
11. DC Offset Control : Pull out the knob to select any DC level of the waveform between ± 10V, turn clockwise to set a positive DC level waveform and invert for a negative DC level waveform.
12. Output Amplitude Control with Attenuation Operation : Turn clockwise for MAX, output and invert for a –20dB output. Pull the knob out for and additional 20dB output attenuation.

12. a) 20dB Attenuation : Press the knob to adjust a –20dB output.
13. MANU/SWEEP Selector and Frequency Adjustment (sweep On/Off) : Press and turn clockwise the knob for MAX frequency and invert for MIN frequency. (Keep the pointer within the scale range on the panel) Pull out the knob to start the auto sweep operation; the upper frequency limit is determined by the knob position.
14. Sweep Time Control and LIN/LOG Selector : I) Rotate the knob clockwise to adjust sweep time for MAX, or invert for MIN. II) To proceed Linear sweep mode by pushing in the knob, or select LOG sweep mode by pulling out the knob.
15. Control MOD ON/OFF Selector : Pull out the knob, the output can be modulated by internal 400Hz. Sine wave or an external signal via VCF/MOD in connector.
16. Sweep Width & Modulation Carrier & AM/FM Selector & FM Selector : I) Sweep width can be controlled from 0 to 1000 times. II) To adjust modulation ratio by turning the knob clockwise for MAX, or invert for MIN. III) Press the knob to get AM function or pull it out for FM function
17. INT/EXT MOD selector : When press the button once, the indicator will lighten, then the EXT MOD has been selected.

 REAR PANEL

18. INT/EXT Counter Selector : Select internal counter mode (count the frequency of model) or select EXT counter mode for an independent counter (input signal from BNC(19)).
19. EXT. counter Input Terminal: Accepts external signals for measurement.
20. TTL/CMOS Output Terminal : TTL/CMOS compatible signal output.
21. VCF/MOD Input Terminal : Used to connect the input voltage required to perform the “voltage control frequency” operation or the EXT modulation operation.
22. Main Output Terminal : Main signal output.
23. GCV Output : This is DC voltage output and its voltage amount will follow the change of Frequency.
24. Power Switch : 115V and 230 V selectable.

USAGE DESCRIPTION

First –step check:

1. Ensure that the voltage of the main supply is compatible with this instrument. The label on the rear panel states the required AC voltage.
2. Connect the instrument to the main supply using the power cord supplied.
3. Press PWR switch (1) and ensure all the rotary controls are pushed in, then rotate AMPL (12) knob to make the indication point up forward.
4. Rotate the FREQ (13) control fully anticlockwise.

 Triangle, square and sine wave.

1. First select Function (8), and select Range (7), rotate FREQ (13), to the set required frequency. (read out from display windows)
2. At this moment, connect Output (22), to oscilloscope for observing output signal, or connect to other experiment circuit.
3. Rotate AMPL (12) again to control waveform amplitude.
4. If attenuation output signal is required, pull out AMPL (12) knob to obtain 20dB attenuation or press (12a) knob for additional 20 dB attenuation.
5. The phase-relation of Output Waveform shown in Figure 1 as below: 

Pulse wave generation

1. First press the key (         ) of Function (8) ; then select Range (7) and rotate FREQ (13), to set required frequency range.
2. Connect output-terminal (22) to oscilloscope for observing output signal.
3. pull out and rotate Duty (9) to adjust the width of pulse waveform.
4. Adjust AMPL (12) knob to control pulse amplitude.
5. Pull out AMPL (12) knob to get 20dB attenuation of output.

 

Ramp wave generation

1. First press the key (          ) of Function (8), then select Range (7) rotate FREQ (13) switch to set required frequency range.
2. Connect output-terminal (22) to oscilloscope foe observing output signal.
3. Pull out and rotate DUTY (() to adjust the slope of ramp waveform.
4. Adjust AMPL (12) knob to control output amplitude of ramp waveform.
5. Pull out AMPL (12) knob to obtain 20dB attenuation of output.

 

TTL/CMOS signal output

1. First select Range (7), rotate FREQ (13) to set required frequency range.
2. Connect BNC connector of TTL/CMOS (20) to oscilloscope or to other experiment circuit for observing output signal.
3. At this moment, output is square waveform fixing to TTL level; suits for general TTL integrated circuit.
4. If square waveform of CMOS level is required, can pull out CMOS (10) knob to adjust voltage level.

 

Variation of external voltage-controlled frequency

This mode of operation allows the user to adjust the frequency of the function generator with an external DC control Voltage. It also provides an easy way for your adjustment.

1. Select Function (8) first, then select Range (7), rotate FREQ (13) to set required frequency range.
2. Connect external control voltage (0 ± 10V) to the VCF (21) connector via a suitable lead, and generate signal from Output (22)
3. Other adjustment, such as AMPL (12) switch can change amplitude of signal, or get attenuation; adjust Offset (11) for DC level, rotate Duty (9) switch can change output signal of pulse or ramp waveform etc.

Basic Instrumentation and Measurement - DC Power Supply

INTRODUCTION

 

The DC power supply is used to generate either a constant voltage (CV) or a constant current (CC). That is, it may be used as either a DC voltage source or a DC current source. We will be using it primarily as a voltage source. Recall that DC is an acronym for direct current. DC means constant with respect to time.

The voltage produced by the power supply is controlled by the knob labeled voltage. The current is limited by adjusting the knob labeled current. As long as the circuit does not attempt to draw more current than the value set by the current knob, the voltage will remain constant.

Current limiting allows the power supply to be set such that it will not generate more current than desired. This can be useful as a safety feature, preventing electrocution due to accidental contact with terminals. In addition, current limiting can prevent damage to equipment and parts which may be unable to handle excessive currents. More details about current limiting will be presented in the experimental procedure. 

Panel Control And Indicator

Front Panel Analog Type

Front Panel Digital Type

FUNCTION DESCRIPTION

FRONT PANEL

1. Power switch : ON/OFF the power input
2. Meter : Indicates the MASTER output voltage (Analog type)

 Indicates the MASTER output voltage or current (Digital type)

3. Meter : Indicates the SLAVE output voltage (Analog type)

 Indicates the SLAVE output voltage or current (Digital type)

4. Meter : Indicates the MASTER output current (Analog type)

A/V selects switch : selects the meter indicates of the slave of the MASTER output voltage or current (Digital type)

5. Meter : Indicates the SLAVE output current (Analog type)

A/V selects switch : selects the meter indicates of the SLAVE output voltage or current (Digital type)

6. Voltage control : for adjustment of the output voltage of the MASTER supply. Also functions as adjustment control for the maximum output voltage of the SLAVE supply when either parallel or series tracking operation.
7. Voltage control : for adjustment of the output voltage of the SLAVE supply when the independent operation.
8. Current control : for adjustment of the output current of the MASTER supply. Also functions as adjustment control for the maximum output voltage of the SLAVE supply when either parallel or series tracking operation.
9. Voltage control : for adjustment of the output current of the SLAVE supply
10. C.V indicator : lights when the MASTER supply is in the constant voltage operation. In either the Series or Parallel  tracking mode, both the MASTER AND SLAVE supplies are in the constant voltage operation.
11. C.V indicator : lights when the SLAVE supply is in the constant voltage operation.
12. C.C indicator : lights when the MASTER supply is in the constant current operation.
13. C.C indicator : lights when the SLAVE supply is in the constant current operation. Also lights when the TRACKING PARALLEL mode is selected.
14. Over load indicator : lights when load on 5 volt supply becomes too large.
15. TRACKING Mode switches: Two push-button switches that select INDEPENDENT mode, series tracking mode, or parallel tracking mode as follows : 

a)      When both switches are disengaged (out), the unit is in the INDEPENDENT mode and the MASTER and SLAVE power supplies are completely independent from one another.

b)      When the left switch is engaged (in) and the right switch is disengaged (out), the unit is in the TRACKING SERIES mode. In this mode, maximum voltage of both supplies is set using the MASTER VOLTAGE controls (voltage at output terminals of the SLAVE supply tracks the voltage at the output terminals of the MASTER supply). Also in this mode of operation the positive terminal (red) of the SLAVE supply is connected to the negative terminal (black) of the MASTER supply. This allows the two supplies to be used as one 0 to double rating voltage supply.

c)      When both switches are engaged (in), the units in the TRACKING PARALLEL mode. In this mode the MASTER and SLAVE supplies are wired together in parallel and both the maximum current and voltage are set using the MATERS controls. The MASTER and SLAVE outputs can be used as two individual (but tracking) power supplies or just the MASTER output can be used as a 0 to rating voltage supply with a 0 to double rating current capability.

16. Same switch as 15
17. “+” output terminal : Positive polarity output terminal for the MASTER supply.
18. “+” output terminal : Positive polarity output terminal for the SLAVE supply.
19.  GND terminal : Earth and chassis ground.
20. GND terminal : Earth and chassis ground.
21. “-“ output terminal : Negative polarity output terminal for the MASTER supply.
22. “-“ output terminal : Negative polarity output terminal for the SLAVE supply.
23. “-“ output terminal : Negative polarity output terminal for 5V supply
24.  “+“ output terminal : Positive polarity output terminal for 5V supply

Rear Panel

25. Fuse holder
26. Power socket
27.  AC select switch : With (28) HI-LO switch selects to permit operation from 100, 120, 220 or 240VAC, 50/60 HZ line voltage.
28.  HI-LO switch : HI position selects high voltage range (120, 240VAC inputs), LO position selects low voltage range (10V, 220VAC inputs)
29. Cooling fan : Ventilates the hot air out, to prevent output stage from thermo shock, and also improves the temperature coefficient.

USAGE DESCRIPTION

 Operation Mode

1. Independent : Two independent outputs and 5V fixed output

Output from 0 to rating volts and 0 to rating amperes.

2. Series : Output from 0 to ± rating volts at rating amperes each.

 Output from 0 to double rating volts at rating amperes.

3. Parallel : Output from 0 to double rating amperes at rating volts.

 Constant Voltage Operation

1. Output current range : 0 – rating voltage continuously adjustable
2. Regulation : Line regulation ≤ 0.01% + 3mV

        Load regulation ≤ 0.01% + 3mV (rating current ≤ 3A)

        Load regulation ≤ 0.02% + 5mV (rating current > 3A)

3. Recovery time : 100µs (50% load change, minimum load 0.5A)
4. Ripple & Noise : ≤ 1mV rms (5Hz-1MHz)
5. Temperature coefficient : ≤ 300 PPM/ºC

 Constant Current Operation

1. Output current range : 0 – rating current continuously adjustable.
2. Regulation : Line regulation ≤ 0.2 % + 3mA

        Load regulation ≤ 0.2% + 3mA

3. Ripple current : ≤ 3mA rms.

 Tracking Operation

1. Parallel Operation

Regulation : Line regulation ≤ 0.01% + 3mV

        Load regulation ≤ 0.01% + 3mV (rating current ≤ 3A)

                                  ≤ 0.02% + 5mV (rating current > 3A)

2. Series operation

Regulation : Line regulation ≤ 0.01% + 5mV

                    Load regulation ≤ 300mV

1. Positive and Negative supply (figure below)

Slave tracking error ≤ 0.5% + 10mV of the master.

B.  Single supply (figure below)

Meter

1. Digital Type
1. Display : 3 – ½ Digits panel meter x 2 (0.5” Red LED display)
2. Accuracy : ± ( 0.5% 0f rdg + 2 digits)
3. Voltmeter : 19.99V of full scale (rating voltage ≤18V), 199.9 of full scale (rating voltage ≥20V)
4. Ammeter : 1.999A of full scale (rating current <>

2. Analog Type
1. Display : Analog Voltmeter and Ammeter each two
2. Class : 2.5
3. Dimension : 50x50 (m/m)

 Insulation

Between chassis and output terminal : 20MΩ or above (DC 500V)

Between chassis and AC cord : 30MΩ or above (DC 500V)

OPERATION INSTRUCTIONS

1. Precaution

i.                    AC input : AC input should be within the range of line voltage ± 10% 50/60 Hz 

ii.                  Installation : Avoid using the supply in a place where ambient temperature exceeds 40ºC. the heat sink located at the rear of the supply must have sufficient air space for radiation.

iii.                Output voltage overshoot : Maybe voltage between output terminals exceeds the present value when the power is turned on or off.

2. Setting Current Limit

i.                    Determine the maximum safe current for the device to be powered.

ii.                  Temporarily short the (+) and (-) terminals of the power supply together with a test lead.

iii.                Rotate the VOLTAGE control away from zero sufficiently for the CC indicator to light.

iv.                Set the meter selection switch to A position to select the current metering mode (Digital type only)

v.                  Adjust the CURRENT control for the desired current limit. Read the current value on the Ammeter.

vi.                The current limit (overload protection) has now been preset. Do not change the CURRENT control setting after this step.

vii.              Remove the short between the (+) and (-) terminal hook up for constant voltage operation.

3. Operation mode

Independent Operation

i.                    Disengage both TRACKING mode switches (both switches out) so that the power supply is in the INDEPENDENT operating mode.

ii.                  Adjust “Voltage” control and “Current” control to the desired output voltage and current.

iii.                Turn off the power supply and the equipment to be powered during hook-up

iv.                Connect the positive polarity of the device being powered to the red (+) terminal of the power supply.

v.                  Connect the negative polarity of the device being powered to the black (-) terminal of the power supply.

vi.                Figure below illustrate the connection procedures.

Series Tracking Operation

i.                    Set the power supplies to the TRACKING SERIES mode by engaging the left TRACKING switch.

ii.                  Set the MASTER A/V switch to the V (voltage metering) position, and the SLAVE A/V switch to the A (current metering) position (digital type only)

(Be careful when connecting power supplies in series to achieve voltages higher than 60V DC total or 60V DC between any connection and earth ground)

iii.                Set the SLAVE CURRENT control to the fully clockwise position. The maximum current is set using the MASTER CURRENT control. Follow the instruction for “Setting Current Limit” (INDEPENDENT USE OF “MASTER” OR “SLAVE” SUPPLY) using the MASTER CURRENT control.

NOTE: Because the supplies are being used in series, either CURRENT control can be used to set maximum current. If desired, the MASTER CURRENT control can be rotated fully clockwise and the SLAVE CURRENT control can be used to adjust the maximum current value. Because current through the two supplies must be equal when they are being used in series, the lowest CURRENT control setting will set the maximum output current.

iv.                Adjust the output voltage to the desired level using the MASTER VOLTAGE controls.

v.                  Turn off the power supply and the equipment to be powered during hook-up

vi.                If “single supply” operation is desired, this allows the power supply to be used as twice the voltage and rating current simply by using the negative (black) terminal of the SLAVE supply and the positive (red) terminal of the MASTER supply. The configuration as shown in figure below

vii.                   If the chassis or  common of the equipment being powered is separate from both the positive and negative polarity power inputs. The output of the SLAVE (negative) supply tracking the output of the MASTER (positive) supply. Configuration as figure below.

Parallel Tracking Operation

i.                    Set the MASTER A/V switch to the V (voltage metering) position, and the SLAVE A/V switch to the A (current metering) position. Output voltage will now be read from the MASTER LED display. Output current is exactly double the value read from the SLAVE LED display (because each supply is providing the same amount of current) (Digital type only)

ii.                  Because both voltage and current of the SLAVE supply track the MASTER supply, the maximum current and voltage are setting using the MASTER controls. Using the MASTER supply output jacks, follow the instructions “Setting Current Limit”. Remember that the actual current output at the MASTER supply output jacks is double the reading on the SLAVE indicator meter.

iii.                Adjust the output voltage to the desired level using the MASTER VOLTAGE controls.

iv.                Turn off the power supply and the equipment to be powered during hook-up.

v.                  Connect the positive polarity of the device being powered to the red (+) terminal of the MASTER power supply.

vi.                Connect the negative polarity of the device being powered to the black (-) terminal of the MASTER power supply. The configuration as below: 

5V Fixed Power Supply Operation

i.                    Turn off the power supply and the equipment to be powered during hook-up.

ii.                  Connect the positive polarity of the device being powered to the red (+) terminal of the 5V supply.

iii.                Connect the negative polarity of the device being powered to the black (-) terminal of the 5V supply.

iv.                If the red OVERLOAD indicator lights, too much load has been placed on the supply. This will cause voltage and current to drop and prevent proper operation of the 5V supply. To correct this situation, the load on the supply must be decreased so that no more than 3 amps of current are required.

Basic Instrumentation and Measurement - Multimeter

A multimeter is a device used to find the electrical problems. It can be used to test resistance and to measure voltage. Resistance can be safely tested with the power off. However, voltage can only be measured with the power on. Because of the risk of electric shock, an individual trained in the use of a voltage tester should only conduct voltage tests.

Safety Information.

-          Don’t try to adjust , test or repair if you don’t have basic repair skills.

-          Always follow the manufacturer’s instructions.

-           Electric Shock can cause injury or death. Never assume the electricity is off. Before servicing an electrical device , disconnect it from its electrical source either by unplugging or turning off the power at the breaker or fuse box.

-          Mark the service panel with a note so that no one will restore power while you are working.

-          After turning off the power to the circuit, test the circuit to be certain that there is no power.

-          Some devices can store a hazardous electrical charge even when disconnected from an electrical source, always discharge these devices before attempting service. If you are unfamiliar with a device or its components, consult with a professional before attempting service.

-          When working with electrical equipment wear rubber-soled shoes, avoid damp locations and hold all tools by their insulated handles. Never touch conductive surfaces such as pipes or metal bracing.

-          Use a non-conductive fiberglass ladder when working with electricity. Avoid shorting electrical circuits.

-          The tests should be done when current is NOT present. Always unplug the device or turn off the main circuit breaker before attempting these tests. Always test your test equipment for proper operation before use.

-          Some multimeters include a fuse, which will sometimes prevent damage to the multimeter if it is overloaded. However the fuse often only protects the highest current range on the multimeter.

-          A common error when operating a multimeter is to set the meter to measure resistance or current and then connect it directly to a low-impedance voltage source; meters without protection are quickly damaged by such errors, and can sometimes explode causing injury to the operator.

-          Digital meters are category rated based on their intended application, as set forth by the CEN EN61010 standard. There are four categories:

o   Category I: used where current levels are low.

o   Category II: used on residential branch circuits.

o   Category III: used on permanently installed loads such as distribution panels, motors, and appliance outlets.

o   Category IV: used on locations where current levels are high, such as service entrances, main panels, and house meters.

Multimeter Layouts

The common multimeter is a small handheld device with an indicator needle over a measurement scale or a numeric LCD display. The device has a switch to select the type of test to be performed. A multimeter also has two wires, one red (+) and one black (-), with metal tips. They are called probes.

1.      Digital Multimeters

·         More accurate , durable and have extra features.

·         Display the measurement in numbers to avoid parallax error.

·         Auto ranging – select the correct range for the device under test to the most significant value are displayed.

·         Auto-polarity – for direct current reading , shows negative sign if it is opposite polarity.

·         Contemporary multimeters can measure many quantities. The common ones are:

                               i.      Voltage in volts.

                              ii.      Current in amperes.

                             iii.      Resistance in ohms.

                             iv.      Additionally, multimeters may also measure:

                             v.      Capacitance in farads.

                            vi.      Frequency in hertz

                           vii.      Duty cycle as a percentage.

                          viii.      Temperature in degrees Celsius or Fahrenheit.

                            ix.      Conductance in siemens.

                             x.      Inductance in henrys

                            xi.      Audio signal levels in decibels.

                            xii.      Digital multimeters may also include circuits for:

                            xiii.      Continuity that beeps when a circuit conducts.

                             xiv.      Diodes and Transistors

2.      Analog multimeters

·    Resolution is limited by scale pointer , vibration of the pointer , accuracy of printing scales , zero calibration , number of ranges and errors due to non-horizontal use of the mechanical display.

·    Error is due miscounting division markings , errors in mental arithmetic , parallax observation errors and less than perfect eyesight.

·    To improve resolution – mirrored scales and larger meter movements.

Probes

There are variety of test probes to connect to the circuit and device under test.

·         Crocodile clips

·         Retractable hook clips

·         Pointed probes

The connectors are attached to flexible, thickly-insulated leads that are terminated with connectors appropriate for the meter. Handheld meters typically use shrouded or recessed banana jacks, while benchtop meters may use banana jacks or BNC connectors. 2mm plugs and binding posts have also been used at times, but are not so common today.

Meters which measure high voltages or current may use non-contact attachment mechanism to trade accuracy for safety. Clamp meters provide a coil that clamps around a conductor in order to measure the current flowing through it.

Application Mode

 

Continuity Test

Continuity is to make sure the thing is electrically connected. We can use a resistance-tester (ohmmeter) to confirm the continuity because the resistance of wire is very small less than 100 Ohms. Sometimes there is buzzer to make the job easier during troubleshooting. This check is important for  :

·         To make sure the soldering is good.

·         To confirm if the wire is broken in the middle e.g inside the insulator.

·         To make sure something isn’t connected. E.g short circuit.

·         To do reverse engineering e.g to verify the design back to a schematic.

 

Analogue Multimeter

This test should be done when current is NOT present. Always unplug the device or turn off the main circuit breaker before attempting a continuity test.

A continuity test is done to determine whether a circuit is open or closed. To test the continuity of a circuit requires the use of a multimeter or multitester.

Set the multimeter to the ohm setting. The symbol for ohm is , the Greek letter omega. If there is more than one ohm setting, choose X1.

Note that while the probes are not touching anything, the multimeter will indicate a reading of infinity. A reading of infinity indicates that the circuit is open and cannot conduct current. When you touch the two probes together, the reading changes to zero. A reading of zero indicates that the circuit is closed and can conduct current. Touch each probe to one of the terminals (or poles) of the device. If the reading changes to zero the device has continuity.

To test a switch, place a probe on each pole of the switch. When you move the switch from the off to the on position, the meter reading should change from infinity to zero, which implies that the switch is working. To test a component such as a motor, touch a probe to each pole. A reading of zero indicates that motor has continuity and current can pass through it.

Digital Multimeters

Put the multimeter into the correct mode. Choose the icon of sound wave. Please refer to the picture.

 

Testing For Ground

This test should be done when current is NOT present. Always unplug the device or turn off the main circuit breaker before attempting a ground fault test.

A ground fault test is done to determine if current is passing from a circuit inappropriately. A ground fault is a potentially dangerous electrical shock hazard. A ground fault can also cause a device to malfunction.

Set the multimeter to the ohm setting. If there is more than one ohm setting, choose X1. Touch one probe to a terminal and touch the other probe to the device's housing or mounting bracket. Now move the first probe to another terminal. If the multimeter displays anything other than a reading of infinity for any of the test combinations, a ground fault exists and the device should be repaired or replaced. Do not use a component that has a ground fault.

 

Measuring Resistance

This test should be done when current is NOT present. Always unplug the device or turn off the main circuit breaker before attempting to measure resistance.

Resistance is how much the flow of current in a circuit is impeded. Resistance is necessary for heat to be generated in heating elements like those used in an electric stove or oven, dryer or hair dryer.

It is necessary to know what the proper resistance rating should be for a particular device in order to determine if it is functioning properly.

Analogue Multimeters

Set the multimeter to the ohm setting. Touch a probe to each of the terminals. The reading on the multimeter should change from infinity to the level of resistance detected in the element. Compare the measurement to the manufacturer's specification for the element.

 

Digital Multimeters

Set the multimeter to the Ohm setting. Touch a probe to each of the terminals. If it has different ranging meters it will have sub mode for different range but if it is auto ranging there will be only one.

 

Measuring for Voltage

·         To test whether the power supply is working.

·         To verify that the circuit is getting enough power.

·         To verify signals to and from chips.

·         Testing batteries , solar cells and power outlets.

·         Test the circuit only when the power is on.

·         Measure the voltage between 2 points. If we need to measure one point , put the negative probe (black) at ground.

·         If we are getting odd readings , we can use reference voltage. (e.g measure a battery)

·         Voltage is directional so make sure the black probe is put correctly at ground.

·         Please select the mode for AC and DC correctly unless told assume it is DC voltage.

Digital Multimeter

There are 2 separate modes for AC and DC. The V with 2 lines (dashed and one solid) is DC and the one with wave line is AC.

Select the correct range. When the probes are not connected it should display 0V.