對(duì)于高要求的工業(yè)環(huán)境，工程師必須考慮惡劣的環(huán)境條件，例如極端溫度、高濕度和大量的水。選擇高溫編碼器時(shí)需要考慮材料和部件例如編碼盤等在高溫下的熱膨脹以及最高預(yù)期溫度下的最大運(yùn)行速度。在指定編碼器用于低溫時(shí)，應(yīng)考慮由于硬化潤(rùn)滑劑引起的熱收縮和額外的啟動(dòng)扭矩。
For high industrial environments, engineers must be account for difficult environmental conditions such as extreme temperatures, high humidity, and large amounts of water. When selecting high temperature encoders need to consider thermal expansion of materials and components such as the encoder disk at high temperatures and the maximum operating speed at the highest expected temperature. When specifying encoders for low temperatures, thermal contraction and additional starting torque due to hardened lubricants should be considered.
溫度對(duì)編碼器性能的影響 Effects of Temperature on Encoder Performance 在光學(xué)編碼器中，碼盤在LED和光電探測(cè)器之間通過(guò)，調(diào)制光束以生成脈沖流，該脈沖流可被處理以產(chǎn)生速度、方向或位置。光學(xué)編碼器使用由玻璃、聚酯薄膜或金屬制成的碼盤。磁性編碼器的工作原理類似，但使用的是磁性材料在磁疇范圍內(nèi)。在這兩種情況下，極端溫度和濕度都會(huì)影響性能、機(jī)械性能和使用壽命。 高溫下的熱膨脹是個(gè)問(wèn)題。在光學(xué)編碼器中，碼盤和源/檢測(cè)器之間的氣隙可以窄至0.020”。根據(jù)溫度、間隙的大小、材料的熱膨脹系數(shù)(CTE)和方向，這種膨脹可能會(huì)使組件相互接觸，從而造成損壞甚至災(zāi)難性故障。 極端溫度也會(huì)損壞碼盤本身。高溫會(huì)使聚酯薄膜變色，導(dǎo)致信號(hào)失真。極端條件會(huì)使碼盤本身變形。熱量還會(huì)使軸承、潤(rùn)滑劑和密封件退化，導(dǎo)致整機(jī)的早期故障。 在采礦、石油和天然氣以及野外應(yīng)用中發(fā)現(xiàn)的低溫會(huì)帶來(lái)一系列不同的問(wèn)題。熱收縮會(huì)使光學(xué)編碼器的碼盤變形，影響信號(hào)質(zhì)量并可能引入異常。軸承和潤(rùn)滑可能會(huì)成為一個(gè)問(wèn)題。潤(rùn)滑油在低溫下會(huì)變硬。如果編碼器一直處于閑置狀態(tài)，則啟動(dòng)時(shí)潤(rùn)滑劑不會(huì)均勻分布在軸承周圍。由于滾動(dòng)體與軸承內(nèi)圈或外圈之間的摩擦，這種情況可能導(dǎo)致軸承部件損壞。潤(rùn)滑劑的稠度也會(huì)大大增加啟動(dòng)扭矩。 以上，我們一直在談?wù)摰氖枪鈱W(xué)編碼器。極端溫度同樣也會(huì)影響磁性編碼器，但影響程度較小。磁輪的膨脹和收縮可以改變磁極的間距，從而改變輸出。氣隙不是問(wèn)題。通常，現(xiàn)代磁性編碼器具有較寬的氣隙（高達(dá) 0.070”），并且由于熱膨脹或收縮引起的任何變化都在可行的氣隙公差范圍內(nèi)。 In an optical encoder, a code disk passes between an LED and a photodetector, modulating the beam to generate either a pulse stream that can be processed to yield speed, direction and/or position. Optical encoders use code disks made of glass, Mylar, or metal. Magnetic encoders operate on a similar principle, but use wheels patterned with magnetic domains. In both cases, extreme temperatures and moisture can impact performance, mechanical properties, and lifetime. Thermal expansion at high temperatures is a problem. In optical encoders, the air gap between the disk and the source/detector can be as narrow as 0.020”. Depending on the temperature, the size of the gap, the coefficients of thermal expansion (CTEs) of the materials, and the orientation, this expansion could bring the components in contact with one another, causing damage or even catastrophic failure. Extreme temperatures can also damage the discs themselves. High temperatures can discolor Mylar, introducing signal distortion. Extreme conditions can distort the disk itself. Heat can also degrade bearings, lubricants, and seals, leading to early failure of the overall unit. Low temperatures such as those found in mining, oil and gas, and off-road applications, present a different set of issues. Thermal contraction can distort the code disk of an optical encoder, affecting signal quality and potentially introducing anomalies. Bearings and lubrication can become a problem. Lubricants harden at low temperatures. If the encoder has been sitting idle, then the lubricant will not be evenly distributed around the bearings at startup. This situation could result in damage to the components of the bearing, due to friction between the rolling elements and inner or outer race of the bearings. The consistency of the lubricant can also substantially increase starting torque. Thus far, we have focused on optical encoders. Thermal extremes also affect magnetic encoders, although to a lesser degree. Expansion and contraction of the magnetic wheel can alter the pitch of the magnetic poles, altering the output. Air gaps are less of an issue. Typically, modern magnetic encoders a have wide air gaps (up to 0.070”) and any variation caused due to thermal expansion or contraction are within the tolerance range of workable airgap. 如何選擇適用于極端溫度的編碼器 How to Choose an Encoder for Extreme Temperatures 所有這些因素使得在指定編碼器時(shí)必須考慮溫度。請(qǐng)注意，超過(guò)推薦的編碼器速度會(huì)降低其熱容差?？紤]額定溫度為-40°C至85°C，建議最高轉(zhuǎn)速為3000轉(zhuǎn)/分的編碼器。每超過(guò)1000轉(zhuǎn)，溫度通常需降低10°C。 確保制造商已使用高加速壽命測(cè)試(HALT)對(duì)設(shè)備進(jìn)行了認(rèn)證。這包括設(shè)計(jì)在受到熱沖擊（溫度的快速和大范圍波動(dòng)）以及振動(dòng)時(shí)的性能。這些條件對(duì)于玻璃代碼盤等易碎組件來(lái)說(shuō)可能是一個(gè)特殊的問(wèn)題。 應(yīng)用程序的性能需求也可能發(fā)揮作用。磁盤質(zhì)量和分辨率之間存在權(quán)衡。玻璃和金屬碼盤有限制。最高分辨率的編碼器使用Mylar碼盤，它更容易受到極端溫度的影響。不要認(rèn)為分辨率越高就越好。編碼器只能報(bào)告位置，它們不能補(bǔ)償系統(tǒng)中的機(jī)械誤差。指定分辨率時(shí)，請(qǐng)務(wù)必選擇實(shí)際有利于應(yīng)用場(chǎng)合的級(jí)別。 All of these factors make it essential to take temperature into account when specifying an encoder. Be aware that exceeding the recommended speed of an encoder will decrease its thermal tolerance. Consider an encoder rated for -40°C to 85°C with a recommended top speed of 3000 RPM. For every 1000 RPM above that speed, the temperature is typically de-rated by 10. Make sure the manufacturer has qualified the unit using highly accelerated lifetime testing (HALT). This includes the performance of the design when exposed to thermal shock (rapid and wide swings of temperature) along with vibrations. These conditions can be a particular problem for fragile components like glass code disks. The performance demands of the application may also come into play. There is a trade-off between the quality of the disk and resolution. Glass and metal code disks are limited. The highest resolution encoders use Mylar code disks, which are more susceptible to temperature extremes. Don’t assume that higher resolution is necessarily better. Encoders can only report position, they cannot compensate for mechanical errors in the system. When specifying resolution, be sure to select a level that will actually benefit the application. 濕度對(duì)編碼器性能的影響 Effects of Humidity on Encoder Performance 水分是一系列應(yīng)用中的問(wèn)題，包括海洋環(huán)境、造紙等工業(yè)制造以及制藥和食品制備等沖洗環(huán)境。濕度會(huì)降低光學(xué)表面的性能，從而衰減光學(xué)編碼器中的信號(hào)。它還會(huì)損壞電子設(shè)備，導(dǎo)致早期故障。這是腐蝕性環(huán)境中的一個(gè)特殊問(wèn)題，例如海洋環(huán)境或那些涉及刺激性化學(xué)品的環(huán)境。對(duì)于這些應(yīng)用，OEM最好選擇具有防護(hù)等級(jí)(IP)評(píng)級(jí)的組件。 IP級(jí)組件專門設(shè)計(jì)用于承受所列條件。例如，IP64組件防塵并且可以承受低壓水噴射，而IP66組件可以處理高壓水射流，而IP67裝置可以防止浸入指定深度。特殊措施包括封裝電子設(shè)備、軸承上復(fù)雜的密封設(shè)計(jì)、密封件和潤(rùn)滑劑的替代材料以及特殊外殼。 根據(jù)分辨率和性能要求，磁性編碼器可能是更好的解決方案。磁性編碼器不受濕氣影響。它們可以在潮濕的環(huán)境中工作，甚至可以完全浸泡在液體中。 在尋找編碼器之前先研究您的應(yīng)用條件。了解IP評(píng)級(jí)系統(tǒng)以選擇能夠提供所需使用壽命周期的設(shè)備。以確保設(shè)備經(jīng)過(guò)適當(dāng)?shù)恼J(rèn)證并發(fā)現(xiàn)任何特殊的安裝要求。 對(duì)于最極端的環(huán)境，最好的反饋選擇可能是解析器。這些設(shè)備不包含任何板載電子設(shè)備。它們?cè)谧類毫拥臈l件下表現(xiàn)良好。 Moisture is a problem in a range of applications including marine environments, industrial manufacturing such as papermaking, and washdown environments like those found in pharmaceutical manufacturing and food preparation. Humidity can degrade optical surfaces to attenuate the signal in optical encoders. It also damages electronics, leading to early failure. This is a particular problem in corrosive environments such as marine environments or those involving harsh chemicals. For these applications, OEMs are best off choosing components with ingress protection (IP) ratings. IP-rated components are designed specifically to survive the conditions listed. IP64 units, for example, are dust tight and can tolerate low pressure water spray, while IP66 components can handle high-pressure water jets, and IP67 units can protect against immersion up to a specified depth. Special measures include encapsulated electronics, sophisticated seal designs on the bearings, alternative materials for seals and lubricants, and specialty housings. Depending on the resolution and performance requirements, a magnetic encoder may be a better solution. Magnetic encoders are not impaired by moisture. They can operate in humid environments and even totally immerse in liquid. Study the conditions of your application before looking for an encoder. Understand the IP rating system to choose a device that will provide the lifetime required. Talk to your vendor to ensure that the devices have been properly qualified and discover any specialty mounting requirements. For the most extreme environments, the best feedback option may be a resolver. These devices do not contain any onboard electronics. 聲明： - 文章轉(zhuǎn)載自DYNAPAR，由愛(ài)澤工業(yè)翻譯，如有侵權(quán)，請(qǐng)聯(lián)系刪除！ - 如有偏頗，歡迎指正！
