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接近傳感器，是代替限位開關(guān)等接觸式檢測方式，以無需接觸檢測對象進(jìn)行檢測為目的的傳感器的總稱。能檢測對象的移動信息和存在信息轉(zhuǎn)換為電氣信號。在換為電氣信號的檢測方式中，包括利用電磁感應(yīng)引起的檢測對象的金屬體中產(chǎn)生的渦電流的方式、捕測體的接近引起的電氣信號的容量變化的方式、利石和引導(dǎo)開關(guān)的方式。
中文名接近傳感器采 用無接點(diǎn)輸出方式構(gòu) 成光電型、磁力型等補(bǔ) 充代替限位開關(guān)等接觸式檢測方式
接近傳感器概要編輯在JIS規(guī)格中，根據(jù)IEC60947-5-2的非接觸式位置檢測用開關(guān)，制定了JIS規(guī)格(JIS C 8201-5-2低壓開關(guān)裝置及控制裝置、第5控制電路機(jī)器及開關(guān)元件、第2節(jié)接近開關(guān))。在JIS的定義中，在傳感器中也能以非接觸方式檢測到物體的接近和附近檢測對象有無的產(chǎn)品總稱為“接近開關(guān)”，由感應(yīng)型、靜電容量型、超聲波型、光電型、磁力型等構(gòu)成。在本技術(shù)指南中，將檢測金屬存在的感應(yīng)型接近傳感器、檢測金屬及非金屬物體存在的靜電容量型接近傳感器、利用磁力產(chǎn)生的直流磁場的開關(guān)定義為“接近傳感器”。
?、?由于能以非接觸方式進(jìn)行檢測，所以不會磨損和損傷檢測對象物。
?、?由于采用無接點(diǎn)輸出方式，因此壽命延長(磁力式除外)采用半導(dǎo)體輸出，對接點(diǎn)的壽命無影響。
?、?與光檢測方式不同，適合在水和油等環(huán)境下使用檢測時幾乎不受檢測對象的污漬和油、水等的影響。此外，還包括特氟龍外殼型及耐藥品良好的產(chǎn)品
?、?與接觸式開關(guān)相比，可實(shí)現(xiàn)高速響應(yīng)
?、?能對應(yīng)廣泛的溫度范圍
?、?不受檢測物體顏色的影響對檢測對象的物理性質(zhì)變化進(jìn)行檢測，所以幾乎不受表面顏色等的影響
?、? 與接觸式不同，會受周圍溫度的影響、周圍物體、同類傳感器的影響包括感應(yīng)型、靜電容量型在內(nèi)，傳感器之間相互影響。因此，對于傳感器的設(shè)置，需要考慮相互干擾。此外，在感應(yīng)型中，需要考慮周圍金屬的影響，而在靜電容量型中則需考慮周圍物體的影響。
感應(yīng)型接近傳感器的檢測原理
通過外部磁場影響，檢測在導(dǎo)體表面產(chǎn)生的渦電流引起的磁性損耗。在檢測線圈內(nèi)使其產(chǎn)生交流磁場，并檢測體的金屬體產(chǎn)生的渦電流引起的阻抗變化進(jìn)行檢測的方式。
此外，作為另外一種方式，還包括檢測頻率相位成分的鋁檢測傳感器，和通過工作線圈僅檢測阻抗變化成分的全金屬傳感器。
在檢測體一側(cè)和傳感器一側(cè)的表面上，發(fā)生變壓器的狀態(tài)。
因?yàn)槲灰苽鞲衅骺梢愿鶕?jù)不同的原理和不同的方法做成，而不同的位移傳感器對物體的“感知”方法也不同，所以常見的傳感器有以下幾種：
電感式傳感器
電感式傳感器也叫渦流式傳感器，由三大部分組成：振蕩器、開關(guān)電路及放大輸出電路。振蕩器產(chǎn)生一個交變磁場，當(dāng)金屬目標(biāo)接近這一磁場，并達(dá)到感應(yīng)距離時，在金屬目標(biāo)內(nèi)產(chǎn)生渦流，從而導(dǎo)致振蕩衰減，以至停振。振蕩器振蕩及停振的變化被后級放大電路處理并轉(zhuǎn)換成開關(guān)信號，觸發(fā)驅(qū)動控制器件，從而達(dá)到非接觸式的檢測目的。由此可見，這種接近開關(guān)所能檢測的物體必須是導(dǎo)電體。
電容式傳感器
這種傳感器的測量通常是傳感器固定處構(gòu)成電容器的一個極板，而另一個極板是在測量過程中通常是接地或與設(shè)備的機(jī)殼相連接。當(dāng)有物體移向傳感器時，不論它是否為導(dǎo)體，由于它的接近，總會使電容器兩極板間的介電常數(shù)發(fā)生變化，從而使電容器的電容量發(fā)生變化，使得和測量頭相連的電路狀態(tài)也隨之發(fā)生變化，由此便可達(dá)到非接觸式的檢測目的。這種接近開關(guān)檢測的對象，不限于導(dǎo)體，可以絕緣的液體或粉狀物等。
霍爾式傳感器
當(dāng)一塊通有電流的金屬或半導(dǎo)體薄片垂直地放在磁場中時，薄片的兩端就會產(chǎn)生電位差，這種現(xiàn)象就稱為霍爾效應(yīng)。兩端具有的電位差值稱為霍爾電勢U，其表達(dá)式為U=K·I·B/d，其中K為霍爾系數(shù)，I為薄片中通過的電流，B為外加磁場(洛倫慈力Lorrentz)的磁感應(yīng)強(qiáng)度，d是薄片的厚度。
由此可見，霍爾效應(yīng)的靈敏度高低與外加磁場的磁感應(yīng)強(qiáng)度成正比的關(guān)系?；魻栐蛯儆谶@種有源磁電轉(zhuǎn)換器件，是一種磁敏元件。它是在霍爾效應(yīng)原理的基礎(chǔ)上，利用集成封裝和組裝工藝制作而成，它可方便的把磁輸入信號轉(zhuǎn)換成實(shí)際應(yīng)用中的電信號，同時又具備工業(yè)場合實(shí)際應(yīng)用易操作和可靠性的要求?；魻栭_關(guān)就是利用霍爾元件的這一特性制作的，它的輸入端是以磁感應(yīng)強(qiáng)度B來表征的，當(dāng)B值達(dá)到一定的程度(如B1)時，霍爾開關(guān)內(nèi)部的觸發(fā)器翻轉(zhuǎn)，霍爾開關(guān)的輸出電平狀態(tài)也隨之翻轉(zhuǎn)。輸出端一般采用晶體管輸出，和其他傳感器類似有NPN、PNP、常開型、常閉型、鎖存型(雙極性)、雙信號輸出之分?；魻栭_關(guān)具有無觸電、低功耗、長使用壽命、響應(yīng)頻率高等特點(diǎn)，內(nèi)部采用環(huán)氧樹脂封灌成一體化，所以能在各類惡劣環(huán)境下可靠的工作。
當(dāng)磁性物件移近霍爾開關(guān)時，開關(guān)檢測面上的霍爾元件因產(chǎn)生霍爾效應(yīng)而使開關(guān)內(nèi)部電路狀態(tài)發(fā)生變化，由此識別附近有磁性物體存在，進(jìn)而控制開關(guān)的通或斷。這種接近開關(guān)的檢測對象必須是磁性物體。
光電式傳感器
光電式傳感器利用的是光電效應(yīng)。將發(fā)光器件與光電器件按一定方向裝在同一個檢測頭內(nèi)。當(dāng)有反光面(被檢測物體)接近時，光電器件接收到反射光后便在信號輸出，由此便可“感知”有物體接近。
利用光電式傳感器制作的光電式接近開關(guān)可以檢測各種物質(zhì)，但是對于流體的檢測誤差較大。
熱釋電式傳感器
熱釋電式傳感器能感知溫度變化，將熱釋電器件安裝在開關(guān)的檢測面上，當(dāng)有與環(huán)境溫度不同的物體接近時，熱釋電傳感器的輸出信號發(fā)生變化，通過對傳感器輸出信號的轉(zhuǎn)化便可檢測出物體的接近。
線性接近傳感器
線性接近傳感器是一種屬于金屬感應(yīng)的線性器件，接通電源后，在傳感器的感應(yīng)面將產(chǎn)生一個交變磁場，當(dāng)金屬物體接近此感應(yīng)面時，金屬中則產(chǎn)生渦流而吸取了振蕩器的能量，使振蕩器輸出幅度線性衰減，然后根據(jù)衰減量的變化來完成無接觸檢測物體的目的。
該接近傳感器具有無滑動觸點(diǎn)，工作時不受灰塵等非金屬因素的影響，并且低功耗，長壽命，可使用在各種惡劣條件下。線性傳感器主要應(yīng)用在自動化裝備生產(chǎn)線對模擬量的智能控制。
在一般的工業(yè)生產(chǎn)場所，通常都選用渦流式接近開關(guān)和電容式接近開關(guān)。因?yàn)檫@兩種接近開關(guān)對環(huán)境的要求條件較低。
當(dāng)被測對象是導(dǎo)電物體或可以固定在一塊金屬物上的物體時，一般都選用渦流式接近開關(guān)，因?yàn)樗捻憫?yīng)頻率高、抗環(huán)境干擾性能好、應(yīng)用范圍廣、價格較低。
若所測對象是非金屬(或金屬)、液位高度、粉狀物高度、塑料、煙草等。則應(yīng)選用電容式接近開關(guān)。這種開關(guān)的響應(yīng)頻率低，但穩(wěn)定性好。安裝時應(yīng)考慮環(huán)境因素的影響。
若被物為導(dǎo)磁材料或者為了區(qū)別和它在一同運(yùn)動的物體而把磁鋼埋在被測物體內(nèi)時，應(yīng)選用霍爾接近開關(guān)，它的價格低。
在環(huán)境條件比較好、無粉塵污染的場合，可采用光電接近開關(guān)。光電接近開關(guān)工作時對被測對象幾乎無任何影。因此，在要求較高的傳真機(jī)上，在煙草機(jī)械上，自動麻將機(jī)、驗(yàn)鈔機(jī)、取電開關(guān)等都被廣泛地使用。
在防盜系統(tǒng)中，自動門通常使用熱釋電接近開關(guān)、超聲波接近開關(guān)、微波接近開關(guān)。有時為了提高識別的可靠性，上述幾種接近開關(guān)往往被復(fù)合使用。
無論選用哪種接近開關(guān)，都應(yīng)注意對工作電壓、負(fù)載電流、響應(yīng)頻率、檢測距離等各項(xiàng)指標(biāo)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
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.
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