DATA PRECISION 1350 User Manual

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62-5008

MODEL

1350

this

step

causes

all

ac

noise

components

of

the

conditioned

Input

that

have

a

whole

number

of

cycles

In

this

Interval

to

average

out

to

zero.

All

50

or

60

Hz

noise

components,

or

multiples

thereof,

meet

this

condition,

and

will

contribute

zero

effects

to

the

output

when

the

Interval

is

exactly

100

milliseconds.

Integration

of

a

Reference

Voltage,

Step

3,

the

voltage

on

the

Integrat

ing

capacitor

(see

Step

2

above)

Is

reduced

at

a

constant

rate

until

end

of

conversion,

when

the

net

Integrator

output

voltage

Is

zero.

The

time

Inter

val

for

this

reduction

Is

"counted",

and

the

accumulated

count

Is

the

digitized

value

of

the

conditioned

Input

signal.

If

the

digitizing

counter

reaches

2000

counts

before

the

Integrator

voltage

Is

reduced

to

zero,

then

the

three

less

significant

digits

are

blanked.

Indicating

an

out-of-

range

conditioned

Input

signal

to

the

A/D

converter.

Step

3

Is

programmed

for

200

milliseconds.

When

end-of-converslon

occurs

within

this

Interval

for

In-range

signals,

the

control

signals

switch

the

circuit

Into

autozero

action

for

the

balance

of

this

step.

This

autozero-

Ing

Is

In

addition

to

the

autozero

of

Step

1.

The

timing

diagram

of

Figure

4-2

summarizes

the

sequence

described

above.

4.4

SIGNAL

CONDITIONING

DETAILS

4.4.1

DCV

Signal

Conditioning

As

shown

In

the

simplified

schematic

of

Figure

4-3,

the

Input

signal

Is

direct-connected

to

the

A/D

Input

for

the

100-mllllvolt

range

(.1),

but

It

Is

connected

across

a

voltage

attenuator

network

for

all

other

range

scale

selections.

Capacitor

03

Introduces

a

filtering

action

along

with

the

series

resistance

of

the

divider

network.

Surge

suppression

components

RV1-

RV5

protect

against

6000V

for

500

nanoseconds.

4.4.2

DCmA

Signal

Conditioning

As

shown

In

the

simplified

schematic

of

Figure

4-4,

the

dc

current

Input

Is

connected

In

series

with

a

protective

fuse

(F301

=

2

amps),

and

then

through

a

shunt

whose

resistance

is

range-selected

to

generate

a

scaled

dc

voltage

output.

The

Input

circuit

Is

protected

by

back-blasing

diodes

CR1

and

CR2

to

limit

the

voltage

that

could

be

developed

across

the

shunt

to

about

1.7

±

0.3V.

4-4

^Copyright

1977.

Data

Precision

Corporation.

All

rights

reserved.

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DATA PRECISION 1350 Specifications

General

Brand	DATA PRECISION
Model	1350
Category	Multimeter
Language	English