Physics 2225: Working With Electronic Equipment How the

wistfultitleElectronics - Devices

Nov 24, 2013 (3 years and 6 months ago)

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Physics
2225: Working
With Electronic Equipment

Purpose


Learn how to use basic electronic
equipment:


D
igital
multi
meter


Oscilloscope


F
unction generator


B
read board


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)

You need to know whether you are measuring an “AC” or “
DC”
current/voltage
and
set your DMM accordingly
. Otherwise
your
measurement
is wrong.

Note: We use the term “DC” or “AC” also for voltages, even though

The “C” stands for “
C
urrent” (Example: 5V DC).

Physics
2225: Working
With Electronic Equipment

Measuring AC with a DMM

V or I

time

AC

If you measure this AC voltage/current in the
“DC” mode,

the result is the

average (averaged over time) value (in this case zero).

average value

If you measure this AC voltage/current in the
“AC” mode,

the result is the

the peak value divided by (assuming a sinusoidal oscillation around zero).

2
A

A
A
707
.
0
2



Always measure AC in the AC mode.

Physics
2225: Working
With Electronic Equipment

Measuring DC with a DMM

V or I

time

DC

If you measure this voltage/current in the
“DC” mode,

the result is the

average (averaged over time) value, which equals the DC value.

average 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.

0.003

COM

V

V

Resistor

5 V

GND

= 0 V

current

A very tiny amount of current

(ideally almost zero) goes

through the voltmeter.

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.

0.003

COM

V

A

Resistor

5 V

GND

= 0 V

current

Important:

Use COM (ground) and
mA

or A (large currents) ports for
current
measurement!

mA

Physics
2225: Working
With Electronic Equipment

NEVER DO THIS !!!!!!!!!!!!!!!!!!!!!!!!!!!

0.003

COM

V

A

Resistor

5 V

GND

= 0 V

huge current

Because the amp meter has almost no resistance, it gives the electrons an easy path
between 5V and ground.


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A

Fuse will blow out !!!

Physics
2225: Working
With Electronic Equipment

The Correct Way, Again

0.003

COM

V

A

Resistor

5 V

GND

= 0 V

current

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).

mA

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

Up to 5 Hz

Up to 50 Hz

Up to 500 Hz

Within each range you can vary the frequency (see next slide).

Physics
2225: Working
With Electronic Equipment

The Function Generator


Frequency Variation

Coarse regulation

Fine regulation

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).

Physics
2225: Working
With Electronic Equipment

The Function Generator


Output Level

Signal output: Connect

BNC cable here.

Adjust the amplitude

of the signal at

“Output Level”.

Physics
2225: Working
With Electronic Equipment

What is “DC Offset” ?

0 Volt

No “DC offset”

0 Volt

2 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 adjustments.

Adjust the amount of

DC offset here.

Physics
2225: Working
With Electronic Equipment

The
Heathkit

“Bread Board”

Called “Bread Board”

because you can use it

to “breed” electric

circuits.


The board allows you

to test your circuits

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
.


Note: Many of our bread
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

Resistor

5 V

GND

5V

R

Circuit Diagram

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

take advantage

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) = 1x2
3
+0x2
2
+0x2
1
+1x2
0

= 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.

5V

5V

0V

0V

1 0 0 1

Physics
2225: Working
With Electronic Equipment

Data Switches, Logic Indicators

The bread board has
“Data Switches”
providing “High” and
“Low
” voltage
for digital
logic .

The bread board also has
LEDs (
L
ight
E
mitting
D
iodes) which act as

logic indicators (a quick
way to find out whether a
voltage is “High” or
“Low”).

Switch

Output

(low or high)

5V

(SW2 up)

0V

(SW4 down)

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).

time

Voltage

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

Change the vertical

scale here.

For more options

on how to use

channel 1 press

the MENU button.

The little knob

shifts the signal

up or down (unless

the cursor is used).

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 at

which cursors 1 and

2 are.

Indicates voltage

difference between

cursor 1 and 2.

Physics
2225: Working
With Electronic Equipment

Time Cursor Selected

The two time

cursors.

Physics
2225: Working
With Electronic Equipment

Connectors and Their Names

“BNC” cable

“Shield”

Center pin

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

Adapter:

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.

Use adapter to plug into DMM

The “Ground” plug

on the BNC/Banana

adapter connects to

the small black clip.

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


DMM, ask your TA for a replacement.

Physics
2225: Working
With Electronic Equipment

Checking Fuse on Mutitec320 DMM is Easy

Just dial to “
mA
” and the

display should look like this.

This symbol indicates

a broken fuse.

Other types of DMMs

have no indicator.