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接近传感器,是代替限位开关等接触式检测方式,以无需接触检测对象进行检测为目的的传感器的总称。能检测对象的移动信息和存在信息转换为电气信号。在换为电气信号的检测方式中,包括利用电磁感应引起的检测对象的金属体中产生的涡电流的方式、捕测体的接近引起的电气信号的容量变化的方式、利石和引导开关的方式。
中文名接近传感器采 用无接点输出方式构 成光电型、磁力型等补 充代替限位开关等接触式检测方式
接近传感器概要编辑在JIS规格中,根据IEC60947-5-2的非接触式位置检测用开关,制定了JIS规格(JIS C
8201-5-2低压开关装置及控制装置、第5控制电路机器及开关元件、第2节接近开关)。在JIS的定义中,在传感器中也能以非接触方式检测到物体的接近和附近检测对象有无的产品总称为“接近开关”,由感应型、静电容量型、超声波型、光电型、磁力型等构成。在本技术指南中,将检测金属存在的感应型接近传感器、检测金属及非金属物体存在的静电容量型接近传感器、利用磁力产生的直流磁场的开关定义为“接近传感器”。
① 由于能以非接触方式进行检测,所以不会磨损和损伤检测对象物。
② 由于采用无接点输出方式,因此寿命延长(磁力式除外)采用半导体输出,对接点的寿命无影响。
③ 与光检测方式不同,适合在水和油等环境下使用检测时几乎不受检测对象的污渍和油、水等的影响。此外,还包括特氟龙外壳型及耐药品良好的产品
④ 与接触式开关相比,可实现高速响应
⑤ 能对应广泛的温度范围
⑥ 不受检测物体颜色的影响对检测对象的物理性质变化进行检测,所以几乎不受表面颜色等的影响
⑦
与接触式不同,会受周围温度的影响、周围物体、同类传感器的影响包括感应型、静电容量型在内,传感器之间相互影响。因此,对于传感器的设置,需要考虑相互干扰。此外,在感应型中,需要考虑周围金属的影响,而在静电容量型中则需考虑周围物体的影响。
感应型接近传感器的检测原理
通过外部磁场影响,检测在导体表面产生的涡电流引起的磁性损耗。在检测线圈内使其产生交流磁场,并检测体的金属体产生的涡电流引起的阻抗变化进行检测的方式。
此外,作为另外一种方式,还包括检测频率相位成分的铝检测传感器,和通过工作线圈仅检测阻抗变化成分的全金属传感器。
在检测体一侧和传感器一侧的表面上,发生变压器的状态。
因为位移传感器可以根据不同的原理和不同的方法做成,而不同的位移传感器对物体的“感知”方法也不同,所以常见的传感器有以下几种:
电感式传感器
电感式传感器也叫涡流式传感器,由三大部分组成:振荡器、开关电路及放大输出电路。振荡器产生一个交变磁场,当金属目标接近这一磁场,并达到感应距离时,在金属目标内产生涡流,从而导致振荡衰减,以至停振。振荡器振荡及停振的变化被后级放大电路处理并转换成开关信号,触发驱动控制器件,从而达到非接触式的检测目的。由此可见,这种接近开关所能检测的物体必须是导电体。
电容式传感器
这种传感器的测量通常是传感器固定处构成电容器的一个极板,而另一个极板是在测量过程中通常是接地或与设备的机壳相连接。当有物体移向传感器时,不论它是否为导体,由于它的接近,总会使电容器两极板间的介电常数发生变化,从而使电容器的电容量发生变化,使得和测量头相连的电路状态也随之发生变化,由此便可达到非接触式的检测目的。这种接近开关检测的对象,不限于导体,可以绝缘的液体或粉状物等。
霍尔式传感器
当一块通有电流的金属或半导体薄片垂直地放在磁场中时,薄片的两端就会产生电位差,这种现象就称为霍尔效应。两端具有的电位差值称为霍尔电势U,其表达式为U=K·I·B/d,其中K为霍尔系数,I为薄片中通过的电流,B为外加磁场(洛伦慈力Lorrentz)的磁感应强度,d是薄片的厚度。
由此可见,霍尔效应的灵敏度高低与外加磁场的磁感应强度成正比的关系。霍尔元件就属于这种有源磁电转换器件,是一种磁敏元件。它是在霍尔效应原理的基础上,利用集成封装和组装工艺制作而成,它可方便的把磁输入信号转换成实际应用中的电信号,同时又具备工业场合实际应用易操作和可靠性的要求。霍尔开关就是利用霍尔元件的这一特性制作的,它的输入端是以磁感应强度B来表征的,当B值达到一定的程度(如B1)时,霍尔开关内部的触发器翻转,霍尔开关的输出电平状态也随之翻转。输出端一般采用晶体管输出,和其他传感器类似有NPN、PNP、常开型、常闭型、锁存型(双极性)、双信号输出之分。霍尔开关具有无触电、低功耗、长使用寿命、响应频率高等特点,内部采用环氧树脂封灌成一体化,所以能在各类恶劣环境下可靠的工作。
当磁性物件移近霍尔开关时,开关检测面上的霍尔元件因产生霍尔效应而使开关内部电路状态发生变化,由此识别附近有磁性物体存在,进而控制开关的通或断。这种接近开关的检测对象必须是磁性物体。
光电式传感器
光电式传感器利用的是光电效应。将发光器件与光电器件按一定方向装在同一个检测头内。当有反光面(被检测物体)接近时,光电器件接收到反射光后便在信号输出,由此便可“感知”有物体接近。
利用光电式传感器制作的光电式接近开关可以检测各种物质,但是对于流体的检测误差较大。
热释电式传感器
热释电式传感器能感知温度变化,将热释电器件安装在开关的检测面上,当有与环境温度不同的物体接近时,热释电传感器的输出信号发生变化,通过对传感器输出信号的转化便可检测出物体的接近。
线性接近传感器
线性接近传感器是一种属于金属感应的线性器件,接通电源后,在传感器的感应面将产生一个交变磁场,当金属物体接近此感应面时,金属中则产生涡流而吸取了振荡器的能量,使振荡器输出幅度线性衰减,然后根据衰减量的变化来完成无接触检测物体的目的。
该接近传感器具有无滑动触点,工作时不受灰尘等非金属因素的影响,并且低功耗,长寿命,可使用在各种恶劣条件下。线性传感器主要应用在自动化装备生产线对模拟量的智能控制。
在一般的工业生产场所,通常都选用涡流式接近开关和电容式接近开关。因为这两种接近开关对环境的要求条件较低。
当被测对象是导电物体或可以固定在一块金属物上的物体时,一般都选用涡流式接近开关,因为它的响应频率高、抗环境干扰性能好、应用范围广、价格较低。
若所测对象是非金属(或金属)、液位高度、粉状物高度、塑料、烟草等。则应选用电容式接近开关。这种开关的响应频率低,但稳定性好。安装时应考虑环境因素的影响。
若被物为导磁材料或者为了区别和它在一同运动的物体而把磁钢埋在被测物体内时,应选用霍尔接近开关,它的价格*低。
在环境条件比较好、无粉尘污染的场合,可采用光电接近开关。光电接近开关工作时对被测对象几乎无任何影。因此,在要求较高的传真机上,在烟草机械上,自动麻将机、验钞机、取电开关等都被广泛地使用。
在防盗系统中,自动门通常使用热释电接近开关、超声波接近开关、微波接近开关。有时为了提高识别的可靠性,上述几种接近开关往往被复合使用。
无论选用哪种接近开关,都应注意对工作电压、负载电流、响应频率、检测距离等各项指标的要求。
The proximity sensor is a general term for the sensor which is replaced by
the contact detection method such as the limit switch, and the sensor is not
required for the detection of the target.. Can detect the moving information and
the information of the object to the electrical signal. In exchange for
electrical signal detection methods, including eddy current generated in the
metal body caused by electromagnetic induction detection object, catching
measured close to the electrical signals caused by changes in the capacity of
the way, illite and guide the switch way.
The Chinese name is close to the sensor output mode with no contact output
mode, and the magnetic type is replaced by the contact detection method such as
the limit switch.
Proximity sensor edit summary in JIS standard, according to the
IEC60947-5-2 the non-contact type position detecting switches, making the JIS
standard (JIS C 8201-5-2 low voltage switch device and a control device, the 5
control circuits, machines and switching element, Section 2 proximity switches).
In JIS definition. In the sensor can also to non-contact way to detect the
objects near and near object detection products collectively as "proximity
switch", by induction, electrostatic capacity type, ultrasonic type,
photoelectric, magnetic type. The DC magnetic field in the technical guide that
will detect metal induction type proximity sensor, detection of metal and
non-metallic objects exist electrostatic capacity type proximity sensor,
produced by the magnetic switch is defined to "proximity sensor".
Because the detection can be carried out in a non-contact way, the object
of the damage detection is not wear and damage detection..
Because of the use of no contact output mode, so the life extension (except
magnetic type) with semiconductor output, the life of the docking point without
influence.
Different from the method of light detection, it is suitable for the
detection of water and oil, etc., almost without the impact of the detection
object and oil, water, etc.. In addition, also includes Teflon shell resistance
and good quality of products
Compared with the contact type switch, can realize high speed response
The temperature range corresponding to widely
Sixthly, is not affected by the detection of the object color of the
detected object changes in physical properties were detected, so is almost not
affected by the surface color
Seventhly, and contact, by ambient temperature influence, influence of
surrounding objects and similar sensors including induction type, capacitance
type, and between the sensor influence each other. Therefore, for the sensor
setting, need to consider mutual interference. In addition, in the induction
type, the influence of the surrounding metals is considered, and the influence
of the surrounding objects is considered in the electrostatic capacity
type..
Detection principle of proximity sensor
The magnetic loss caused by eddy current caused by eddy current is detected
by the magnetic field.. The detection of the magnetic field caused by the
magnetic field in the detection coil, and the detection method of the eddy
current caused by the eddy current caused by the body of the body is
detected..
In addition, as an additional way, the detection of the frequency of the
phase components of the aluminum detection sensor, and through the work coil
only detect the total metal sensor impedance change components.
On the surface of the side of the detector and on the side of the sensor,
the transformer is in the condition of the transformer..
Because displacement sensor can be based on different principles and
different methods to make, and different displacement sensor of object
perception method is different, so the common sensor have the following:
Inductive sensor
Inductive sensor is also called the eddy current sensor, which consists of
three parts: the oscillator, the switching circuit and the amplified output
circuit. The oscillator generates an alternating magnetic field, when the metal
target is close to the magnetic field, and when the induction distance is
generated, the vortex flow in the metal target, resulting in the oscillation
attenuation and stop vibration. The change of the oscillator oscillation and the
stop vibration is processed and converted into the switch signal, and the
trigger drives the control device, so as to achieve the non-contact detection..
Thus, the proximity switch can detect the object must be a conductor.
Capacitive sensor
The sensor measurement is usually a sensor fixed in which a plate of the
capacitor is a plate, and the other plate is usually a ground or the device in
the measurement process.. When objects move sensor, regardless of whether it is
a conductor, due to its proximity, always make between the two plates of the
capacitor dielectric constant change, and so changes the capacitance of the
capacitor, the measuring head is connected with the circuit state change, which
can achieve the non-contact detection. This proximity switch detection object,
not limited to conductors, can be insulated from liquid or powder etc..
Holzer type sensor
When a generic current of metal or semiconductor wafer is vertically placed
in a magnetic field, at the two ends of the sheet will produce potential
difference, this phenomenon is known as the Hall effect. Potential difference at
both ends of said to Hall voltage U and its expression is U=K - I - B/d, where k
is the hall coefficient, I is a slice through the current, B is applied the
magnetic induction intensity of the magnetic field (Luolunci force Lorrentz) and
D is the thickness of the sheet.
Thus, the sensitivity of the Holzer effect is proportional to the magnetic
induction intensity of the applied magnetic field.. The Holzer element belongs
to this kind of active magnetoelectric converter, which is a magnetic sensitive
element. It is in based on the Hall effect principle, the use of integrated
packaging and assembly production process and, it can be convenient for the
magnetic input signal is converted to electrical signals in the practical
application, but also have industrial applications practical application to be
easy to operate and
Linear proximity sensor is a metal induction linear device belongs to,
after the power is switched on, in the sensing surface of the sensor will
produce an alternating magnetic field, when the metal objects close to the
induction surface, metal produces eddy current and absorb the energy of the
oscillator, the oscillator output amplitude of linear attenuation, then
according to the changes of reduction of aging to complete the non contact
detection object.
The proximity sensor has no sliding contact, the impact of non metal
factors such as dust when working, and low power consumption, long life, can be
used in all kinds of harsh conditions. The linear sensor is applied in the
intelligent control of the analog quantity of the automatic equipment production
line..
In general industrial production sites, the eddy current type proximity
switch and the capacitive proximity switch are usually used.. Because these two
kinds of proximity switch to the environment of the requirements of the
lower.
When the object to be measured is conductive objects or can be fixed on a
metal object, are generally used eddy current proximity switch, because of its