Weighing technology has been valued by people since ancient times, as a
A measurement method, widely used in industry and agriculture, scientific research, transportation,
Various fields, such as domestic and foreign trade, are closely connected with people's lives.
The electronic automatic scale is a kind of electronic weighing instrument, and the weighing instrument is a national law
Fixed measuring instruments are important for national defense construction, national economy and people's livelihood, domestic and foreign trade,
Indispensable measurement equipment for scientific research, technical level of weighing instruments
level, it will directly affect the modernization level of all walks of life
flat improvement. The weighing device is not only a monomer that provides weight data
instruments, but also as industrial control systems and business management systems
An integral part that advances the automation and management of industrial production
modernization. The advanced and precise electronic sorting scale will surely shorten the work
time, improved operating conditions, reduced energy and material consumption,
Improve product quality, strengthen enterprise management, and improve business management.
The application of weighing devices has spread to all fields of the national economy, and has achieved
significant economic benefits. At present, our country has been replaced by traditional mechanical
Weighing instrument step into the set of sensors, microelectronics technology, computer technology
The stage of development of electronic weighing instruments with integration. due to electronic scales
Fast weighing, convenient reading, able to work under harsh conditions, convenient
Combining with computer technology to realize weighing technology and process control
The automation characteristics have been widely used in industrial and mining enterprises, energy
Various directions such as transportation, commercial trade and science and technology. This article is
It is based on the wide application of weighing sensors at present, and the current
How to choose the appropriate sensor in the manipulator.
Sensor selection is a very complicated issue, its
Correct or not will directly affect the success or failure of the test system. usually
We are based on factors such as sensitivity, maximum and minimum scale values, etc.

to consider.

2 Selection of the number of sensors and range
The choice of the number of sensors is based on the use of the electronic scale, scale body
Depends on the number of support points required. In general, there are several support points
Just choose a few load cell sensors.
The measuring range of the sensor is based on the number of sensors, the maximum scale
The weighing value, the self-weight of the scale, and the dynamic load factor are determined.
The following is a calculation derived from a lot of experience
Formula: C=K0×K1×K2×K3 (Wmax+W)/N
Where: C is the rated range of the sensor W is the self-weight of the scale body
Wmax is the maximum net weight of the measured object; N is the number of support points of the scale body
K0 Wind pressure coefficient K1 Insurance coefficient K2 Impact coefficient K3 Center of gravity deviation
shift coefficient
Select the solution for the sensor on the manipulator:

The phenomenon that the resistance of a conductor changes with mechanical deformation is called electrical resistance.
Resistive strain effect, the resistance strain gauge is converted to △R/R by signal
Finally, since the corresponding resistance changes are generally very small, it is difficult to directly measure
Accurate measurement, and inconvenient to handle. Therefore, it is necessary to use the conversion
The circuit converts the change of △R/R into the change of current or voltage. convert
The circuit usually uses a bridge circuit

Option 1 Piezoelectric sensor
Piezoelectric sensor is a typical active sensor, also known as
Self-generating sensors. Its working principle is based on the fact that certain materials are
The piezoelectric effect that generates charges on its corresponding specific surface after the force.
Piezoelectric sensors are small in size, light in weight, simple in structure and reliable in operation.
Rely, it is suitable for the measurement of dynamic mechanical quantities, not suitable for measuring frequency too
Low measurands, let alone measure static quantities. Currently mostly used for acceleration
Measurement of degrees and dynamic force or pressure. Piezoelectric Weaknesses: High
Internal resistance, small power, small power, weak output energy, cable
The distributed capacitance and noise interference affect the output characteristics, which is external
The circuit is very demanding.
Option 2 capacitive sensor
The capacitive sensor converts the change of the measured non-electric quantity into
A sensor for capacitance changes. It has good dynamic response, structural
Simple, high sensitivity, can realize non-contact measurement, with average
effects etc. Capacitive sensors can be used to detect force, displacement, pressure
force, and vibrational non-electrical parameters. How Capacitive Sensors Work
It is expressed by ordinary parallel plate capacitors. two parallel gold
It is a polar plate, when it does not consider the edge effect, the capacitance is:
C=εrε0A/d
In the formula: d——distance between two polar plates; A—parallel polar plates
effective area; εr—permittivity of the medium; ε0—in vacuum
dielectric constant.
If the measured change makes the three parameters of εr, ε0 and A in the formula
Any change in the quantity will cause a change in the capacitance, through
The measurement circuit can then be converted into electrical output. Although capacitive sensing
The device has many advantages such as simple structure and good dynamic characteristics, but also
There are disadvantages:
(a) Low power, high impedance. Limited by geometry, the capacitance
The capacitance of the sensor is very small, generally only a few picofarads to tens of picofarads
Law. Because C is too small, the capacitive reactance XC=1/wC is very large, which is high impedance
components, poor load capacity; and because of its apparent power P=u0
2
ωC,C
is small, then P is also small. Therefore, it is susceptible to external interference, and the signal needs to be
Zoom in and take anti-jamming measures.
(b) The initial capacitance is small, the cable capacitance, the stray circuit of the line
The parasitic capacitance formed has a great influence.
Scheme 3 resistance strain sensor
Resistance strain sensor is a kind of resistance strain effect,
A structural sensor that converts various mechanical quantities into electrical signals. electricity
The core component of the resistance strain gauge type resistance strain sensor, its working
The principle of operation is based on the resistance strain effect of the material, and the resistance strain gauge
Can be used alone as a sensor, but also can be combined with elastic
The elements constitute the force sensor.