DATA PRECISION 1350 User Manual

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62-5008

MODEL

1350

Chapter

4

PRINCIPLES

OF

OPERATION

4.1

GENERAL

Model

1350

DMM

employs

the

ratiometric

technique

of

a

dual

ramp

inte

grating

A/D

converter

to

obtain

a

digitized

value

for

display.

The

AID

conversion

is

accomplished

in

a

monolithic

integrated

circuit

in

which

a

dc

voltage

proportional

to

the

measured

parameter

(voltage,

current,

resistance)

is

"ratioed"

with

respect

to

a

standard

reference

voltage.

This

chapter

includes

a

description

of

how

each

input

parameter

is

trans

formed

into

a

scaled

dc

voltage

according

to

the

selected

measuring

func

tion,

signal

conditioning

mode,

and

range

scale.

It

also

includes

descrip

tion

of

the

operation

of

the

circuit

elements

that

digitize

and

display

the

measured

value.

4.2

SYSTEM

BLOCK

DIAGRAM

(Figure

4-1)

As

shown

in

Figure

4-1,

voltages

or

resistances

to

be

measured

are

con

nected

between

input

terminals

J400

and

J402.

Voltages

are

attenuated

by

a

factor

determined

by

the

range

selection,

and

the

attenuated

signal

either

by-passes

or

is

connected

to

the

AC/DC

converter

as

determined

by

the

front

panel

selection

of

dc

or

ac

respectively.

The

resulting

dc

signal,

at

a

sensitivity

of

0.1

volts

per

1000

counts,

is

one

input

to

the

integrating

AID

converter.

A

reference

supply

of

0.1

volts

is

the

refer

ence

input

for

voltage

and

current

measurements

(as

described

later).

The

voltage

developed

across

a

range-scale-selected

standard

resis

tance

is

the

reference

voltage

for

kilohm

measurements.

Currents

to

be

measured

are

connected

via

input

terminals

J401

and

J402

through

a

range-selected

shunt

resistance

so

that

the

resulting

vol

tage

is

scaled

at

a

sensitivity

of

0.1

volts

per

1000

counts

(100

millivolts

full

scale).

In

all

measurements,

the

range

selection

that

attenuates

the

input,

or

that

determines

the

standard

resistance

in

kilohms

measurement,

automati

cally

positions

the

decimal

point

in

the

display

for

direct

reading

capability.

The

measuring

function

selection

also

controls

the

power

to

the

polarity

display

digits

so

that

the

sign

(-i-

or

-)

can

be

lighted

for

dc

measuring

functions

only

(voltages

and

currents).

^Copyright

1977.

Data

Precision

Corporation.

All

rights

reserved.

4~

1

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DATA PRECISION 1350 Specifications

General

Brand	DATA PRECISION
Model	1350
Category	Multimeter
Language	English