Heathkit IG-18 User Manual

84 pages

To Next Page

To Next Page

To Previous Page

To Previous Page

Page #60 background image

Loading...

Page #60 background image

Page

52

SQUARE WAVE TESTING

Square

waves

are

very

useful

for

testing

ampli-

fiers,

since

one

square

wave

will

perform

several

tests

simultaneously.

This

occurs

be-

cause

the

square

wave

is

actually

a

complex

waveform

made

up of

many

sine

waves,

which

are

the

fundam

ental

frequency·

and

all

of

the

odd

har-

monics

ofthat

frequency.

Therefore,

in

one

oper-

ation,

the

square

wave

tests

a

circuit

at

many

dif-

ferent

frequencies,

from

one

tenth

to

ten

times

the

fundamental

frequency.

The

flat

top

of

the

square

wave

tests

the

low

fre-

quency

response

of a

circuit.

This

happens

be-

cause

the

flat

top

more

closely

resembles

low

frequencies,

or

short

burst

of

DC

voltage.

The

vertical

portion

of

the

square

wave

contains

high

harmonic

frequencies

that

test

the

response

of

the

amplifier

to

about

ten

times

the

fundamen-

tal

frequency.

Thus,

two

settings,

100 Hz

and

10 kHz

would

check

the

frequency

response

of

an

amplifier

from

10 Hz

to

100,000 Hz.

Figure

8

shows

the

types

of

square

wave

re-

sponse

patterns

that

might

be

seen

on

an

oscil-

loscope.

If

the

corners

of

the

square

wave

are

rounded

off,

it

means

that

some

of

the

higher

harmonics

are

missing.

If

the

flat

top

portion

of

the

square

wave

is

tilted,

it

means

that

the

low

frequency

response

of

the

amplifier

is

faulty.

Square

wave

tests

are

also

an

excellent

way

to

test

the

response

of

the

vertical

amplifiers

of

an

oscilloscope.

Connect

the

square

wave

to

the

os-

GOOD

POOR

HIGH

FREQUENCY

RESPONSE

cilloscope

vertical

input

and

check

the

shape

of

the

square

wave

on

the

oscilloscope

screen.

The

sine

wave

and

square

wave

outputs

of

your

Generator

can

be

used

at

the

same

time

without

detrimental

effects

to

either

waveform.

This

makes

the

use

of

recurrent

sweep

oscilloscopes

especially

easy

with

this

instrument.

For

example,

when

making

stage

gain

measure-

ments

on

an

amplifier

with

an

oscilloscope,

connect

the

sine

wave

output

of

the

Generator

to

the

input

of

the

stage

being

measured.

Con-

nect

the

square

wave

output

to

the

external

sync

connector

of

the

oscilloscope.

Measurements

can

now

be

made

through

a

number

of

amplifier

stages

without

readjusting

the

oscilloscope

sync

controls,

of how

sm

all

or

how

large

the

signal

SPECIAL

GENERATOR APPLICATIONS

Impedance Measurements

Figures

how

to

measure

the

input

iIrIPE:ctalll(~e

an

amplifier

or

of a

similar

circuit.

m~~tllod

is

exact

if

the

impedance

if

it

is

reactive,

For

Impei::1aI1CE!S

that

are

high

com-

impedance,

use

the

9A.

It

may

be

V!ll'i,~hllp

resistors

of

several

as

10

100

kn,

1

Mn,

correct

indication

on

the

EXCESSIVE

HIGH

FREQUENCY

RESPONSE

Figure

8

Questions and Answers:

Need help?

Do you have a question about the Heathkit IG-18 and is the answer not in the manual?

Heathkit IG-18 Specifications

General

Brand	Heathkit
Model	IG-18
Category	Test Equipment
Language	English

Related product manuals

Heathkit IO-4550

Preview: Heathkit IT -3120

Heathkit IT -3120