Heathkit IM-4100 - Page 49

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GSeguEeatTHKIT?

Unknown

Frequencies

To

measure

an

unknown

frequency,

push

the

POWER/TIME

BASE

switch

to

kHz.

Then

apply

the

unknown

frequency

to

the

counter

input.

If

the

OVERRANGE

indicator

lights

up,

the

frequency

is

higher

than

99.999

kHz

and

the

POWER/TIME

BASE

switch

should

be

pushed

to

MHz.

If

the

display

then

constantly

changes

in

a

random

manner,

the

frequency

is

higher

than

the

Counter’s

capability,

or

the

input

level

is

too

low.

The

Display

Frequencies

lower

than

100

kHz

can

be

read

directly

to

a

resolution

of

+1

Hz

in

the

kHz

position

of

the

POWER/TIME

BASE

switch.

Frequencies

of

100

kHz

and

higher

(within

the

range

of

the

Counter)

can

be

read

to

+1

Hz

by

using

both time

base

positions.

A

frequency

of

12,345,678

Hz

would

be

displayed

as

follows:

POWER/TIME

BASE

Display

Overrange

Switch

Indicator

MHz

12.345

~

Off

kHz

45.678

On

ACCURATE

LOW

FREQUENCY

MEASUREMENTS

Your

Frequency

Counter

counts

and

displays

low

frequency

signals.

However,

the

display

error

will

be

+1

count

because

the

clock

in

the

Counter

is

not

synchronized

with

the

incoming

signal.

To

measure

a

low

frequency

signal

more

accurately,

position

the

POWER/TIME

BASE

switch

to

mS

and

the

MODE

switch

to

PER.

Then

solve

for

the

equation

f

=

1/period.

Page

43

Example:

Accurately

count

a

10

Hz

signal

from

a

signal

generator.

The

period

display

is

99.991

mS.

Solve

for

f

=

1/period

=

1/.099991

=10.0009

Hz.

NOTES:

ie

Noise

on

the

input

signal

can

cause

large

errors

in

this

type

of

measurement

as

noise

will

make

the

Schmitt

trigger

switch

either

early

or

late.

2%

When

possible,

use

fast

rise-time

signals

(square

waves

instead

of

sine

waves).

Noise

on

square

wave

signals

has

less

time

to

influence

the

Schmitt

trigger

and

thus

error

is

substantially

reduced.

TOTALIZE

MEASUREMENTS

In

the

TOL

mode,

the

Counter

adds

up

(totalizes)

the

input

pulses

until

the:

1.

Input

pulses

stop.

2

RESET

button

is

pushed.

(This

clears

the

count

to

zero

so

the

count

will

be

1

with

the

next

input

pulse.)

3.

Count

is

stopped

by

a

logic

O

at

the

rear

panel

INPUT/OUTPUT

connectors

when

__

the

OSCILLATOR

switch

is

in

the

EXT

position.

12-VOLT

OPERATION

The

Counter

will

operate

normally

on

DC

power

except

the

POWER/TIME

BASE

switch

does

not

turn

the

Counter

off.

The

Counter

will

remain

on

as

long

as

the

DC

power

is

applied.