Tachometer and uses the principle of classification
Speed tables are essential equipment machinery industry is one used to determine
motor speed, line speed or frequency. Commonly used in motors, fans, paper, plastics,
chemical fiber, washing machines, cars, planes, ships and other manufacturing
industries. Speed measurement in all areas of the national economy are essential.
First, speed detection instrument Category:
Centrifugal tachometer: The balance between centrifugal force and tension to indicate
speed. Centrifugal speed meter is the most traditional speed measurement tools is the
use of centrifugal force principle of mechanical tachometer; measurement accuracy is
generally 1 to 2, the general in-place installation. A good centrifugal tachometer is not
only accurate and intuitive features, it also has the advantages of reliable and durable.
But the structure is complicated.
Magnetic tachometer: use rotating magnetic field, generated in the metal cover cap on
the spin, rotating force and the balance hairspring force to indicate speed. Magnetic
tachometer, is an example of successful use of magnetic force, the principle of the use
of magnetic mechanical tachometer; normal locally installed, with the flexible shaft
can be a short distance off-site installation. Magnetic tachometer, because the
structure is relatively simple, now more commonly used motorcycles and cars and
other machinery and equipment. Off-site installation, flexible shaft damaged. Electric
speed table: from the small AC generators, cables, motors and magnetic properties of
the composition of the table header. Small alternator produces alternating current,
alternating current through the cable transmission, drive a small AC motor, a small
AC motor shaft speed and measured speed line. Magnetic head and a small AC motor
speed coaxial connection with the magnetic head table is indicative of the speed of the
natural axis of rotation measured; electric speed, off-site installation is very easy,
vibration performance, widely used in diesel engines and marine equipment.
Electromagnetic tachometer: magnetic sensor plus ammeter, remote installation is
Flash-type tachometer: The principle of persistence of vision. Flash-style tachometer,
in addition to detect speed (reciprocating speed), but also the cycle can be observed
moving object still image, on the understanding of the work of the state machinery
and equipment is a necessary observation tool.
Electronic tachometer: electronic technology advances, so that this type of speed
Table With rapid development.
The 6 speed device, has its own unique structure and principle, not only represent
different stages of technological development, but also reflect the phased nature of
human knowledge development. Time is constantly advancing, some things will
become history; but we care to recall, can not help but marvel forerunners of
Centrifugal tachometer, is the outcome of mechanics;
Magnetic-type tachometer, is the use of magnetic and mechanical strength of a model;
Electric tachometer, clever use of micro-generation and micro-motor will be rotating
Electromagnetic tachometer, ammeter and sensor head is the growing popularity of
Flash-style tachometer, human understanding of nature while recognizing the self,
reflects the human soul;
Electronic tachometer, electronic technology, the ever-changing, to the colorful world
of today, also created to meet the various needs of people speed measuring
Second, electronic tachometer
Electronic Tachometer is a more general concept: modern electronic technology,
design and manufacture of speed measurement tool. It generally has sensors and
monitors, and some are signal output and control. Sensors and display devices as
diverse areas, as well as the diversity of measurement methods, as hard as before to
classify 5. This will be electronic tachometer, the second instrument from the sensors
and separate categories. If the mode from the installation points, there are locally
mounted, desktop, counter-mounted and portable and handheld. This paper makes
Speed sensor from the principle (or device) up points, there are magnetic induction,
the photoelectric effect-type, Hall-effect, magnetoresistive effect type,
electromagnetic induction and other media. Another indirect measurement speed of
rotation sensors: acceleration sensor, such as (by integral operation, indirect export
speed), the displacement sensor by differential operation, indirect export speed), and
so on. Speed generators and some of the magnetic sensor linear region can be directly
converted by AC RMS to measure the speed; most of the output pulse signal (sine or
square wave approximation). Speed pulse signal measured for the method are: the
frequency integral method (that is, F / V conversion method, the direct result of
voltage or current), and frequency methods (a direct result of figure).
Speed indicator display instrument from the direct form of divided pointer, digital,
and hybrid graphics and virtual instrumentation;
Moving coil: coil, gossamer pointer together on a rotating shaft, the input current to
the coil, the coil induces a magnetic force, and proportional to each other; magnetic
force and torque balance hairspring, torque and pointer rotation proportional to the
angle of the pointer also reflect The size of the input current;
Moving Magnet Type: quadrature coil current changes, leading to synthesis of the
magnetic field changes direction, and a pointer attached to the single-pole permanent
magnet on, the indicators reflect the current changes.
Electric type: two-way rotation of the motor driven rotary potentiometer,
potentiometer input signal voltage sample value and compared to determine
bi-directional rotary motor forward and backward, or stop, and the potentiometer
linkage pointer accurately reflect the size of the input signal.
The three-pointer to class type header, the header is electric electronics, dynamic
moving coil magnetic-type header and the header are not part of electronics, when and
header matching the header-driven sensor or power supply when needed and rely on
modern electronic technology, put it here classified as electronics.
2. Digital, graphics and mixed:
Mainly from the device to distinguish, with digital control, field type LCD, LCD
screen, fluorescent tubes, screens, plasma screens and EL screens. Display
Technology is a specialized technology, this will involve a number of display
technology, but do not do start set.
3. Virtual speed table:
With the popularization of computer, computer display and operating platform to do
the virtual instrument, but also more widely used, the current mainstream
development platform NI&#39;s LabVIEW. The development and application of
technology, you can visit the NI&#39;s website.
Third, rotational speed measuring method
F / V converter electronic speed measuring devices, the speed sensor and the header
(display) component. The most commonly used speed sensors, most of the output
pulse signal, as long as the current transition through the frequency and voltage and
current input type can be a pointer to the table and the table match, or directly sent to
PLC; frequency current conversion methods RC integration, the charge pump method
and the ASIC Act, the first two methods in magnetic tachometer also have use of.
Most ASIC is the number of RC integration, the integrated charge pump method.
ASIC currently used, there are LM331, AD654, and VF32, etc., the conversion
accuracy of more than 0.1%; but in low frequencies, this conversion can not do
anything. By MCU or FPGA, to do F / D and D / A converter, conversion accuracy is
0.5 ~ 0.05%, and range from 0 ~ 2Hz to 0 ~ 20KHz, frequencies below 10Hz to
reflect the longer time. On the F / V conversion, please refer to the corresponding chip
description and application information, this magazine.
In the display accuracy, reliability, cost and flexibility in the use of certain
requirements, you can type directly using tachometer pulse frequency operation.
Frequency calculation method, and a timer counting method (frequency measurement
method), a set number of time method (measured perimeter method) and the counting
time synchronization method.
Time counting method (frequency measurement method) in the measurement error of
± 1, low speed when the error is relatively large; a set number of time method
(measured perimeter method) are ± 1 time units of the error, at high speed, errors are
Counting time synchronization method combines the advantages of both methods, the
entire measurement range reaches a high accuracy measurement of more than five ten
thousandths tachometer are basically the method.