电子秤翻译

In order to solve the weight problem often encountered in measuring the low-mass

objects

in

the

trade

and

daily

life

of

the

modern

business,

the

design

of

a

new

pocket- sized

electronic

scales.

This

pocket-sized

electronic

scales

Force

Sensor

gravity

signals

into

electrical

signals

to

measure,

and

measuring

the

results

of

the

digital display. The pocket-sized electronic scales with a small size, light weight, easy

to carry, intuitive display, measurement and high precision; complex structure, the

cost disadvantages. This article focuses on the load cell works, error compensation,

the main parameters of selection. And the technical and economic analysis.

1

A

needs

analysisIn

modern

commerce

and

trade

and

everyday

life,

often

encounter the problem of measuring the weight of the low-mass objects. Although

the

traditional

steelyard

can

solve

this

problem,

but

inconvenient

to

carry,

the

efficiency

is

not

high,

the

display

is

not

intuitive

and

low

measurement

accuracy;

mechanical

spring

balance

can

solve

this

problem,

but

the

inertia

inherent

low

frequency, high sensitivity, measurement accuracy is not high. With the progress and

update

of

the

micro-computer

technology,

integrated

circuit

technology,

sensor

technology, electronic scales rapid development, it has a responsive, high accuracy,

fully functional, the display is intuitive, compact, easy to use and so on.

For these reasons, in order to solve the low-mass objects weighing problem, if a

small

size,

light

weight,

portable,

digital

display

electronic

scales,

will

be

popular.

Discussed

below,

that

is,

the

scope of

a

weighing

5

kg

compact

electronic

scales.2

DesignThe principle of the structure of the pocket-sized electronic scales shown in

Figure 1. The main task is to design compact electronic scales weighing the choice of

the

force

sensors.

Dynamometer

sensor

types

to

achieve

the

weighing

and

digital

display, the key is to want to force (gravity) signals into electrical signals to measure

method is mainly divided into two categories: one is the direct method, namely the

use of pressure magnetic sensor, piezoelectric sensor, Piezoresistive sensors directly

to the force signal converted into electrical signals; the other is the indirect method,

the elastic element as the sensor will pull, pressure changes in strain, displacement,

or

frequency,

and

then

strain

sensors,

displacement

sensors,

or

frequency

sensor

strain, displacement or frequency changes for power. Comprehensive comparison of

a

variety

of

sensors,

use

the

indirect

method

of

strain

gauge

force

-sized electronic scale structural principle:

Sensor → amplifier → CPU → display → A?D converter

3 sensor device design

3.1 worksThe working principle of the strain gauge force

transducer

strain

gauge

pasted

into

force,

force-sensitive

elastic

element,

the

corresponding strain when the elastic element force deformation, the strain gauge

into

a

resistance

change,

which

led

to

the

voltage

measuring

circuit

changes

by

measuring

the

output

voltage

value,

and

then

through

the

conversion

can

be

obtained

by

the

measurement

of

body

weight.

Since

the

pocket- sized

electronic

scales

require

small

size,

weighing

in

scope,

precision

and

angle

even

consistency,

sensor

and

display

integration,

it

is

selected

parallel

to

the

two

holes

cantilever

beam strain gauge load-bearing sensor. Its characteristics are: high precision, ease of

processing,

simple

and

compact

structure,

strong

resistance

to

partial

load,

high

natural

gauge

choice

of a

metal

palisade

metal

mooring

paste on

the

insulating

substrate

parked

strain

gages,

mechanical

strain

resistance

strain

gauge

feelings

generally

10

-

10

-

2mm,

the

resistance

rate

of

change

of

the

attendant about 10 - 6 10 - 2 orders of magnitude, such a small change in resistance

measured using the general resistance of the instrument is hard to measure out, you

must use some form of measurement.

Circuit into small changes in resistance rates to changes in voltage or current, in

order

to

secondary

instrument

display.

Bridge

measurement

circuit

to

meet

this

requirement.

In

the

load

cell,

R

1,

R

2,

R

3,

R

44

strain

gauge

resistor

bridge

measurement

circuit

shown

in

Figure

3.

R

m

is

the

temperature

compensation

resistor, e is the excitation voltage, V is the output voltage.

The load cell is a quality signal into a measurable electrical signal output device.

Must consider the actual working environment of the sensor which sensor Yin, this is

essential for the correct selection of the load cell, and it is related to the sensor can

work as well as its safety and service life, and the whole weighing the reliability and

safety sex. On the basic concepts and methods of evaluation of the major technical

indicators of the load cell, the new and old GB qualitative differences.

The

traditional

concept,

the

load

sensor

weighing

sensors,

force

sensors,

collectively

referred

to

using

a

single

parameter

to

evaluate

its

measurement

properties.

Old

GB

will

be

completely

different

application

objects

and

the

use

of

environmental conditions

consider, not given to distinguish between the test and evaluation methods. Old GB

total

of

21

indicators,

were

tested

at

room

temperature;

and

non-linearity,

hysteresis

error,

repeatability

error,

creep,

the

additional

error

of

the

zero

temperature

and

the

maximum

error

in

the

six

indicators

of

the

rated

output

additional temperature error, to determine said The level of accuracy of the weight

sensor, respectively 0.02,0.03,0.05 said.

Proportion to convert the output signal can be measured. Taking into account

the different place of use of the acceleration due to gravity and air buoyancy on the

conversion,

the

main

performance

indicators

of

the

load

cell

linearity

error,

hysteresis

error,

repeatability

error,

creep,

zero-temperature

characteristics

and

temperature

sensitivity characteristics.

In

a

variety

of

weighing

and

measuring

the

quality of the system, usually the integrated error accuracy of the integrated control

sensors,

and

integrated

error

band

or

scale

error

band

(Figure

1)

linked

so

that

selection corresponds to a certain accuracy weighing weighing sensors. International

Organization

of

Legal

Metrology

(OIML)

requirements,

sensor

error

with

total

weighing instrument error δ with Δ of 70% of the load cell linearity error, hysteresis

error

within

the

specified

temperature

range

due

to

the

effect

of

temperature

on

the sensitivity of the error the sum can not exceed the error band of δ. This allows

the

manufacturer

of

the

components

that

make

up

the

total

measurement

error

adjustment to obtain the desired accuracy.