### Physics 2225: Working With Electronic Equipment How the

Physics 2225: Working With Electronic Equipment
Purpose
Learn how to use basic electronic
equipment:
•
•
•
•
Digital multi meter
Oscilloscope
Function generator
Apply and verify Ohm’s laws.
Physics 2225: Working With Electronic Equipment
Digital Multi Meter (“DMM”)
A DMM is a device to measure
• voltage,
• current,
• resistance,
• and more….depending on the model
There are two modes to measure voltage and current:
•“AC” (alternating current)
•“DC” (direct current)
Note: We use the term “DC” or “AC” also for voltages, even though
The “C” stands for “Current” (Example: 5V DC).
You need to know whether you are measuring an “AC” or “DC”
current/voltage and set your DMM accordingly. Otherwise your
measurement is wrong.
Physics 2225: Working With Electronic Equipment
Measuring AC with a DMM
V or I
A
 0.707 A
2
A
AC
average value
time
If you measure this AC voltage/current in the “DC” mode, the result is the
average (averaged over time) value (in this case zero).
If you measure this AC voltage/current in the “AC” mode, the result is the
the peak value divided by 2 (assuming a sinusoidal oscillation around zero).
 Always measure AC in the AC mode.
Physics 2225: Working With Electronic Equipment
Measuring DC with a DMM
V or I
DC
average value
time
If you measure this voltage/current in the “DC” mode, the result is the
average (averaged over time) value, which equals the DC value.
 Always measure DC in the DC mode.
Physics 2225: Working With Electronic Equipment
Setting AC or DC on DMM (Fluke 87)
DC voltage
AC voltage
Current:
Switch between
DC and AC by
pushing the
blue button.
Physics 2225: Working With Electronic Equipment
Setting AC or DC on DMM (MultiTec 320)
Voltage:
Put dial to “V”.
Switch between
DC and AC by
pushing the
DC/AC button.
Current:
Put dial to mA or A.
Switch between
DC and AC by
pushing the
DC/AC button.
Physics 2225: Working With Electronic Equipment
Measuring a Voltage with the DMM
Voltmeters have very high resistance.
 Very little current will flow through a voltmeter even if V is high.
 It is hard to damage a voltmeter.
Voltmeters are connected “in parallel” to measure the voltage
between two points.
A very tiny amount of current
(ideally almost zero) goes
through the voltmeter.
0.003
5V
current
Resistor
GND
=0V
V
COM V
Important: Use COM (ground) and V ports for voltage measurement!
Physics 2225: Working With Electronic Equipment
Measuring a Current with the DMM
Current meters (“amp meters”) have very low resistance.
 When hooked up to an even small voltage difference, a large current would
flow through a current meter.
 It would be easy to damage a current meter.
 Current meters are protected by a fuse (if you blow the fuse the current
meter will no longer work until the fuse is replaced).
Amp meters are connected “in series” to measure the current in a circuit.
5V
current
0.003
A
Resistor
GND
=0V
mA COM V
Important: Use COM (ground) and mA or A (large currents) ports for current measurement!
Physics 2225: Working With Electronic Equipment
NEVER DO THIS !!!!!!!!!!!!!!!!!!!!!!!!!!!
huge current 5 V
0.003
A
Resistor
GND
=0V
A COM V
Fuse will blow out !!!
Because the amp meter has almost no resistance, it gives the electrons an easy path
between 5V and ground.  Huge current through amp meter will blow the fuse.
Physics 2225: Working With Electronic Equipment
The Correct Way, Again
5V
current
0.003
A
Resistor
GND
=0V
mACOM V
Notice
If you follow the path of the current you can see that it is forced to go through the resistor,
which limits its current (by Ohm’s law….Current = Voltage / Resistance).
Physics 2225: Working With Electronic Equipment
The Function Generator
•
•
•
•
•
Time-varying voltage/current.
Three different wave shapes (sinusoidal, square, triangular).
Variable frequency.
Variable amplitude of the signal.
DC offset of signal.
Physics 2225: Working With Electronic Equipment
The Function Generator – Wave Shape
Selection
Sinusoidal Wave
Square Wave
Triangular
(“Sawtooth”)
Wave
Physics 2225: Working With Electronic Equipment
The Function Generator – Frequency Range
Within each range you can vary the frequency (see next slide).
Up to 5 Hz
Up to 50 Hz
Up to 500 Hz
Physics 2225: Working With Electronic Equipment
The Function Generator – Frequency Variation
Display of frequency:
For low frequencies
you need to wait a few
seconds for the correct
value to show (it takes
time to measure it).
Coarse regulation
Fine regulation
Physics 2225: Working With Electronic Equipment
The Function Generator – Output Level
of the signal at
“Output Level”.
Signal output: Connect
BNC cable here.
Physics 2225: Working With Electronic Equipment
What is “DC Offset” ?
No “DC offset”
0 Volt
2 Volt
0 Volt
Signal has “DC offset”
of + 2 Volts (the signal
fluctuates around
+2 V instead of 0 V).
Physics 2225: Working With Electronic Equipment
The Function Generator – Generating a “DC
Offset”
Push “DC OFFSET”
Button IN to enable
DC offset here.
Physics 2225: Working With Electronic Equipment
because you can use it
to “breed” electric
circuits.
The board allows you
before you build a
permanent version.
Physics 2225: Working With Electronic Equipment
The Heathkit “Bread Board” – the Actual “Board”
This is the board:
Makes connecting
electric components
(resistors, capacitors,
integrated circuits…)
EASY.
Physics 2225: Working With Electronic Equipment
How the “Holes” are Connected
5 holes in a
“column” are
electrically
connected.
But:
Red and Green
are NOT connected
across the center break.
The center break
Physics 2225: Working With Electronic Equipment
How the “Holes” are NOT Connected
Holes in a
“row” are
electrically
NOT connected.
Physics 2225: Working With Electronic Equipment
How the “Holes” are NOT Connected
Top break
Holes are NOT
connected
across the top break.
boards do not have the
double row above the top
break any more.
Physics 2225: Working With Electronic Equipment
Power Supply to the Bread Board
Main Power: Switches all voltages
ON or OFF.
GND = 0 Volts (“Ground”)
Example:
To get 5 Volts:
Use GND and +5
Physics 2225: Working With Electronic Equipment
Example of Setting up a Simple Circuit
R
Circuit Diagram
5V
5V
Resistor
GND
A more pictorial view of the
same circuit.
Physics 2225: Working With Electronic Equipment
And How it Looks on the Bread Board
Physics 2225: Working With Electronic Equipment
And from Another Angle…..
Notice, how we
of the hidden
connections
between the
holes in a
column.
Physics 2225: Working With Electronic Equipment
Binary Numbers
In digital electronics information is coded as binary numbers which
contain only Ones and Zeroes.
Example: 1001 (binary) = 1x23+0x22+0x21+1x20 = 9 (decimal)
Any decimal number can be converted to a binary number and stored
electronically (e.g., in a computer).
1’s and 0’s are often stored as High (5Volt) and Low (0 Volt) voltages.
For example, the number shown above (1001) could be represented
by 4 “data lines” that have either high or low voltages.
1
0
5V 0V
0
1
0V 5V
Physics 2225: Working With Electronic Equipment
Data Switches, Logic Indicators
“Data Switches”
providing “High” and
“Low” voltage for digital
logic .
Switch
Output
(low or high)
0V
(SW4 down)
5V
(SW2 up)
LEDs (Light Emitting
Diodes) which act as
logic indicators (a quick
way to find out whether a
voltage is “High” or
“Low”).
Physics 2225: Working With Electronic Equipment
Resistor Color Code
Our resistors have 4 colored bands on them. See your manual for color
code.
Gold = 5% uncertainty
First band
Red = 2
Second band
Black = 0
Third band
Brown = Multiplier 10 W
Resistance = 2 0 * 10 W = 200 W  10 W
Physics 2225: Working With Electronic Equipment
The Oscilloscope
A device to display a voltage as a function of time (useful for voltages that vary
with time – e.g. oscillating signals). You can display 2 signals simultaneously
using the two input channels (Ch.1 and 2).
Voltage
time
Channel 1 input
Channel 2 input
Physics 2225: Working With Electronic Equipment
Changing the Horizontal (Time) Scale
Change horizontal
time scale here.
Physics 2225: Working With Electronic Equipment
Changing the Vertical Scale on Channel 1
The little knob
shifts the signal
up or down (unless
the cursor is used).
For more options
on how to use
channel 1 press
Change the vertical
scale here.
Physics 2225: Working With Electronic Equipment
Using the Cursor
Press the CURSOR
button to enable the
cursors.
Once the cursor
button is pushed
these two knobs
move the two
cursors.
Physics 2225: Working With Electronic Equipment
Using the Cursor
Change the type of
cursor between
voltage cursor or
time cursor with this
button.
Indicates voltage
difference between
cursor 1 and 2.
Indicates voltage at
which cursors 1 and
2 are.
Physics 2225: Working With Electronic Equipment
Time Cursor Selected
The two time
cursors.
Physics 2225: Working With Electronic Equipment
Connectors and Their Names
Center pin
“BNC” cable
“Shield”
A BNC cable is basically a double cable:
One “cable” is the center conductor ending in the center pin.
The other “cable” is the “shield”.
 A BNC cable can do the job of two parallel wires.
Physics 2225: Working With Electronic Equipment
An Adaptor Used in this Lab
BNC (female)
to Banana (male)
“Ground” indicator:
Indicates that this side
of the banana end connects
to the “Shield” of the BNC
connector.
The other banana end connects
to the center conductor of the
BNC.
Physics 2225: Working With Electronic Equipment
Suggestion for Using Cables and DMM
BNC
small clips easily
attach to resistors etc.
The “Ground” plug
on the BNC/Banana
the small black clip.
Use adapter to plug into DMM
Physics 2225: Working With Electronic Equipment
More…..
• More and different types of cables can be throughout room
405 hanging on the walls.
• There are also more and other types of adapters in the
brown cabinet labeled “L” to the left of the entrance or
they may be on the shared table.
• Should – against all warnings – you blow a fuse on your