Download Practice use of the Digital Multimeter.

CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Name:
Derek Molloy
Title:
E3 The Digital Multimeter (DMM).
Class:
CIMC2
Report Date:
05 May 2007
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Practical Technologies (CIMC2): E3 The Digital Multimeter
1) Abstract:
This report discusses a lab experiment to practice the use of the Digital Multimeter by
taking measurements of many different components.
The report shows the competence of the user in verifying component values and taking
circuit readings.
____________________________________________
2) Introduction:
As part of this Lab exercise I’ve given details of my personal DMM. I’ve also supplied
a note on safety precautions to be aware of when carrying out voltage and current
measurements. This is followed by detailed information on the how to set up the meter
for the different applications.
The main body of the exercise covers the measurements and calculations taken on
the 13th of January 2007 where resistances, currents and voltages were taken of
combinations of resistors. An oscilloscope was used on the day to compare and verify
RMS voltage readings. Theoretical calculations were used to compare and verify
readings. The forward break down voltage of a diode was measured. Finally the values of
capacitors were measured.
____________________________________________
3) Main body of Report
All readings were taken with my own personal Multimeter details below:
Fluke 789 ProcessMeter™
Double your power.
Fluke combined a loop calibrator and a
DMM to give process technicians double
the power in one tool (the Fluke 787). Now
we made it even better "the ultimate loop
calibration multimeter" the Fluke 789
ProcessMeter. The 789 has a display that's
not only twice as large, but also twice as
bright with two levels of backlighting. With
its built-in, selectable 250 ohm HART®
resistor, it eliminates the need to carry a
separate resistor with you. Now process
technicians can do a lot more while
carrying a lot less.
Figure 1
Key features of the Fluke 789

24 V Loop power supply
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Practical Technologies (CIMC2): E3 The Digital Multimeter

HART mode setting with loop power (adds 250 ohm resistor)

100 % larger dual display

1,200 ohm drive capability on mA source

Enhanced backlight with two brightness settings

0-100 % mA Span Check buttons to toggle between 4 and 20 mA

Infrared I/O serial port compatible with FlukeView? Forms Software Version 2.1
(available Feb. 2003)

Externally accessible fuses for easy replacement

DMM designed to meet 1000 volt IEC 1010 CAT III standards

Precision 1000 V, 440 mA true-rms digital multimeter

Frequency measurement to 20 kHz

Min/Max/Average/Hold/Relative modes

Diode Test and Continuity Beeper

Simultaneous mA and % of scale readout

20 mA dc current source / loop calibrator / simulator

Manual Step (100 %, 25 %, Coarse, Fine) plus Auto Step and Auto Ramp

Externally accessible battery for easy battery changes

IR communication port allows data to be logged to optional FlukeView Forms®
software for graphical analysis and reporting
Safety:
Conforms to European Union
Directive 73/23/EEC
EN61010-1, CAT III and CAT IV
Note: to practice the use of the Digital Multimeter by taking measurements of many
different components. It is essential that the DMM is set up to the correct mode and that
the leads are in the correct sockets. Further more it is essential to ensure that there is no
voltage present for resistance or diode tests and that the maximum voltage or current
measurement limits are not exceeded to prevent damage to the DMM or the user.
The user has to ensure that all precautions are taken to avoid electrocution when taking
measurements on high voltage circuits and charged capacitors (when constructing
circuits involving capacitors it is essential that they are orientated correctly to avoid them
burning out). Only a competent user should be using the equipment. If there is any
uncertainty regarding the safe use of the equipment of safety to them selves they should
seek advice prior to use of the equipment.
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Practical Technologies (CIMC2): E3 The Digital Multimeter
To measure resistance
Setup meter mode to read resistance.
Connect the leads across the CAT III 1000V
The meter can be left on “Auto Range” or “Manual Range”.
Table 1
To measure voltage
Setup meter mode to read either AC voltage.
Setup meter mode to read either DC voltage
Connect the leads across the CAT III 1000V
The meter can be left on “Auto Range” or “Manual Range”.
Table 2
To measure current
Setup meter mode to read either AC or DC current (Automatic
selection).
Connect the leads across the 0.44A FUSED for AC or DC up to
0.44A
Connect the leads across the 30mA FUSED for DC up to 30mA
The meter can be left on “Auto Range” or “Manual Range”.
Table 3
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Practical Technologies (CIMC2): E3 The Digital Multimeter
Part (1). Resistor Values and DMM Voltage.
Set up DMM to measure resistance (as in Table 1). Connect the leads across the
selected resistors and record the resistance values (Results in Table 4)
Set up DMM to measure voltage (as in Table 2). Connect the leads across the selected
resistors and record the voltage values (Results in Table 4)
Resistor Values
DMM Voltage Units
Units (Ohms)
(Volts DC)
119.6
2.316
148.1
2.316
180.0
2.316
56.0
2.681
Table 4
Part (2). Resistor Values and DMM Current.
Set up DMM to measure resistance (as in Table 1). Connect the leads across the
selected resistors and record the resistance values (Results in Table 5)
Set up DMM to measure current (as in Table 3). Connect the leads in line the selected
resistors and record the current values (Results in Table 5)
Resistor Values
Units (Ohms)
119.6 + 56 (L1 + L4)
148.1 + 56 (L2 + L4)
180.0 + 56 (L3 + L4)
(119.6, 148.1, 180.0) + 56 (L4)
Table 5
DMM Current
Units (Amps DC)
0.028
0.024
0.021
0.047
Part (3). Resistor Values, Oscilloscope Route Mean Square (RMS)
Amplitude and DMM RMS Voltage.
Set up DMM to measure resistance (as in Table 1). Connect the leads across the
selected resistors and record the resistance values (Results in Table 6)
Set up DMM to measure voltage (as in Table 2). Connect the leads across the selected
resistors and record the voltage values (Results in Table 6)
Verify the measured voltage with Oscilloscope set to read RMS Amplitude Volts AC.
Resistor Values
Oscilloscope RMS Amplitude
DMM RMS Voltage
Units (Ohms)
Units (Volts AC RMS)
Units (Volts AC RMS)
119.6
0.509
0.51
148.1
0.509
0.51
180.0
0.509
0.51
825.0
7.07
6.96
3300.0
7.07
6.96
Table 6
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Practical Technologies (CIMC2): E3 The Digital Multimeter
Comparison of DMM RMS Voltage versus Oscilloscope RMS Amplitude
0.001
0.51  0.509  0.001 
 0.002 X 100  0.2%
0.51
&
0.11
6.96  7.07  0.11 
 0.0158 X 100  1.58%
6.96
Part (4). Measured AC current through the parallel combination of the
3.3kΩ and 820Ω resistors:
Set up DMM to measure current (as in Table 3). Connect the leads in line the selected
resistors and record the current values (Results in Table 7)
0.011Amps AC
( at 7.43Volts AC)
Table 7








7.43
Volts


 Amps 
Verification:
  0.0113125 A
Re sis tan ce






 

1
1


  656.796 
 1

1  
1

  3300  820   656.796 

 



Part (5). Calculated effective resistance of the combination:
Set up DMM to measure resistance (as in Table 1). Connect the leads across the
selected resistors and record the resistance values.
Verification:

 





1

   1   660
1   1 
 1


 

 3300 825   660 
Part (6). Theoretical value of the combination:

 


 

1
1


  656.796
1  
1
 1



 

 3300 820   656.796 
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Practical Technologies (CIMC2): E3 The Digital Multimeter
Part (7). Condition of a diode using the diode test function of the DMM:
To measure diode condition.
Setup meter mode to read the forward break down voltage of the
diode by selecting the mode and pressing the blue button.
Connect the leads across the CAT III 1000V
The meter will read “Manual Range 4” and give DC voltage reading.
Table 8
Part (7). (Continued)
Set up DMM to measure diode condition (as in Table 8). Connect the leads across the
selected diode and record the voltage values (Results in Table 6)
0.495 Volts DC
Table 9
Part (8). Values of the capacitors measured with DMM:
Set up DMM to measure capacitance. Connect the leads across the selected capacitor
and record the capacitance values (Results in Table 10)
Capacitor Value
Units ( µF )
10
15
22
DMM Measured Capacitance
Units (µF)
7.16
14.9
20.8
Table 10
____________________________________________
4) Conclusion:
The objective of this lab to practice taking measurements of resistors, capacitors
and diodes using a digital multimeter is to develop and improve the proficiency of a new
user to the use of a digital multimeter. The exercise shows the variations likely to be
found between the recorded value versus the stated value of different devices. Also the
possibility of inaccuracies due to errors being introduced through various quality of
connection to devices, the allowable tolerances of the devices, the addition of test leads
and the possibility of errors in the measurement instrument.
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Practical Technologies (CIMC2): E3 The Digital Multimeter
The values of the resistances fell within the tolerances stated on the devices. The
Comparison of DMM RMS Voltage versus Oscilloscope RMS Amplitude gave an
accuracy of 0.2 to 1.58% which is very good because of the combination of allowable
tolerances in the DMM and the Oscilloscope. The larges errors were found between the
capacitors values and the measured value of the DMM which could have been due to
quality of connection to devices, the allowable tolerances of the devices, the addition of
test leads and the possibility of errors in the measurement instrument.
But over all the values recorded come second to the experience gained from the
exercise.
____________________________________________
5) References:
http://www.hach-korea.com/data/789-05.jpg
http://us.fluke.com/usen/products/Fluke+789.htm?catalog_name=FlukeUnitedStates
Back to home Page:
http://Derek.Molloy.ie/
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