加速度計和速度傳感器的區(qū)別（中英文）
要確定是否應(yīng)該使用加速度計或速度傳感器，首先重要的是要了解它們之間的區(qū)別。加速度計是一種機械裝置，用于測量結(jié)構(gòu)或機器運動或加速度的變化。然后這種運動被轉(zhuǎn)換成可以測量的電信號。通常，加速度計可用于測量沖擊力或機器的振動。
To determine whether you should use an accelerometer or velocity sensor, it is first important to understand the difference between them. An accelerometer is a mechanical device used to measure the change in motion or acceleration of a structure or machine. This motion is then converted into an electrical signal that can be measured. Often an accelerometer can be used to measure the force of impact, or the vibration of a machine.
速度傳感器不是測量絕對位置，而是使用振動裝置來測量位置隨著時間的變化。然后它計算這個變化以確定速度。
Instead of measuring an absolute position, a velocity sensor uses a seismic device to measure changing positions over time. Then it calculates this change to determine the velocity.
為了更好地確定哪種測量形式最適合具體情況，請閱讀以下內(nèi)容以確定是應(yīng)該使用加速度計還是速度傳感器。
To better determine which form of measurement is most ideal for your specific situation, read the following steps to determine whether should use an accelerometer or a velocity sensor.
第 1 步：確定要測量的內(nèi)容
Step 1: Determine what you want to measure
一般經(jīng)驗如下：
The general rules of thumb are as follows:
? 如果轉(zhuǎn)子可以相對于外殼移動，對實際軸運動，必須使用接近探頭。
If the rotor can move relative to the casing, and you are interested in actual shaft motion, you must use a proximity probe.
? 對套管運動，應(yīng)該使用振動傳感器（速度傳感器或加速度計）；選擇使用哪種傳感器應(yīng)考慮傳感器在不同頻率下提供的信號強度。
If you are interested in casing motion, you should use a seismic transducer (velocity sensor or accelerometer); your choice of which to use should be governed by considering the signal strength the transducer will provide at the frequency(ies) of interest.
? 如果因為某些應(yīng)用選擇加速度計，信號強度可能非常?。ㄐ∮趲缀练?，并且很容易被系統(tǒng)中的噪聲淹沒，從而很難將信號與噪聲分開。
If you choose an accelerometer for certain applications, the signal strength can be very small (less than a few millivolts) and can easily be swamped by the noise in the system, making it hard to separate signal from noise.
? 盡管壓電速度傳感器只是帶有內(nèi)部積分器的加速度計，但它可以為監(jiān)視器中的集成提供更好的結(jié)果。這也是因為傳感器發(fā)出的信號強度（以 mV 為單位）相對于噪聲強度（以 mV 為單位）。
Although a piezo-velocity sensor is just an accel with an internal integrator, it gives superior results to integration in the monitor. This again is because of signal strength (in mV) coming out of the sensor relative to the strength of the noise (in mV).
? 在低速和中速旋轉(zhuǎn)時，壓電速度傳感器通常是一個不錯的選擇；在低轉(zhuǎn)速下，加速度計通常是一個糟糕的選擇，但在中高轉(zhuǎn)速下是一個不錯的選擇。
A piezo-velocity sensor is usually a good choice at low and medium rotative speeds; an accel is usually a poor choice at low rotative speeds, but a good choice at medium and high rotative speeds.
請記住，對于油膜軸承機器，通常使用軸觀察接近探頭，但往復(fù)式機器除外。盡管往復(fù)式機器具有支撐曲軸的油膜軸承，但機器非常堅硬，曲軸和外殼之間幾乎沒有相對運動，因此在這種情況下，安裝在外殼上的傳感器將是更好的應(yīng)用。對于滾動軸承機器，轉(zhuǎn)子和外殼之間的相對運動非常小，因此安裝在外殼上的傳感器通常是更好的應(yīng)用。一個例外是具有非常大的滾動軸承的緩慢移動的轉(zhuǎn)子；在這種情況下，由于軸運動緩慢且滾動軸承可能磨損，接近探頭可能是監(jiān)控機器狀況更好的傳感器。
Remember for a fluid film bearing machines you generally want to use shaft observing proximity probes, an exception is for reciprocating machines. Even though the reciprocating machines have fluid film bearings supporting the crankshaft, the machines are so stiff there is little to no relative motion between the crankshaft and the casing, so casing mounted transducers would be a better application in this case. For rolling element bearing machines, there is very little relative motion between the rotor and the casing, so casing-mounted transducers are usually the best application. An exception is for slow-moving rotors that have very large rolling element bearings; in this case, a proximity probe may be the best sensor for machine conditions due to the slow shaft motion and the possibility of rolling-element bearing wear.
第 2 步：確定頻率
Step 2: Determine the frequencies of interest
? 大多數(shù)與轉(zhuǎn)子相關(guān)的故障（不平衡、不對中、金屬與金屬摩擦、不穩(wěn)定、軸裂紋、保持架缺陷等）出現(xiàn)在 1/4X 到 3X 之間（1X = 轉(zhuǎn)子速度，以每分鐘轉(zhuǎn)數(shù) (rpm)、cps、或赫茲）。
Most rotor-related malfunctions (unbalance, misalignment, metal to metal rubs, instability, shaft cracks, cage flaws, etc.) appear between 1/4X to 3X (1X = rotor speed, measured in revolutions per minute (rpm), cps, or Hz).
? 大多數(shù)滾動軸承缺陷發(fā)生在外圈滾珠通行頻率的 1 至 6 倍范圍內(nèi)（簡單地說，BPFO ~ #Elements x RPM / (2 x 60sec/min) = Y cps 或 Y Hz）。
Most rolling-element bearing defects occur in the region of 1 to 6 times the Ball Pass Frequency Outer Race (simply put BPFO ~ #Elements x RPM / (2 x 60sec/min) = Y cps, or Y Hz).
? 較高的振動頻率可能是由于葉片通過率、齒輪嚙合、BPFO 頻率的諧波以及其他振動諧波（葉片通過率 = # 葉片 x 轉(zhuǎn)子速度 (1X)，齒輪嚙合頻率 = # 齒輪齒數(shù) x 轉(zhuǎn)子速度 (1X) ），諧波是振動波形不是完美正弦波時產(chǎn)生的基本強迫頻率的倍數(shù)）。
Higher vibration frequencies may be a result of blade passage rate, gear mesh, harmonics of BPFO frequency, and other vibration harmonics (blade passage rate = # blades x rotor speed (1X), gear mesh frequency = # gear teeth x rotor speed (1X), harmonics are multiples of the fundamental forcing frequencies generated when the vibration waveform is not a perfect sine wave).
? 撞擊事件是激發(fā)高階頻率的寬帶能量來源。
Impact events are a source of broadband energy that excites higher-order frequencies.
示例：離心泵，帶有七個葉片葉輪，運行速度為 3000 rpm，帶有滾動元件軸承，每個軸承有 10 個滾動元件，需要監(jiān)控。頻率為：
1X = 3000 rpm = 50 cps = 50 Hz
1/4X 至 3X = 12.5 至 150 cps = 12.5 至 150 Hz，對于與轉(zhuǎn)子相關(guān)的故障
BPFO 大約 = 10 個元件 x 50 cps / 2 = 250 cps = 250 Hz
BPFO 的 1 至 6 倍 = 250 至 1500 cps = 250 至 1500 Hz，用于軸承相關(guān)故障 葉片
通過率 = 7 x 50 cps = 350 cps = 350 Hz
Example: A centrifugal pump, with a seven blade impeller, operating at 3000 rpm, with rolling element bearings, with 10 rolling elements per bearings needs monitoring. The frequencies of interest are:
1X = 3000 rpm = 50 cps = 50 Hz
1/4X to 3X = 12.5 to 150 cps = 12.5 to 150 Hz, for rotor related malfunctions
BPFO approximately = 10 elements x 50 cps / 2 = 250 cps = 250 Hz
1 to 6 times the BPFO = 250 to 1500 cps = 250 to 1500 Hz, for bearing related malfunctions
Blade Passage Rate = 7 x 50 cps = 350 cps = 350 Hz
人們會選擇一種安裝在套管上的傳感器，該傳感器至少可以測量12.5 赫茲至 1500 赫茲。
One would select a casing-mounted transducer that could measure at least 12.5 Hz to 1500 Hz.
第 3 步：確定所需的套管傳感器靈敏度
Step 3: Determine the required casing transducer sensitivity
一般來說，高頻時加速大，低頻時加速小。位移正好相反：高頻時位移小，低頻時位移大。不同頻率下的速度往往更加恒定。下圖顯示了當(dāng)速度保持恒定而改變頻率范圍時位移和加速度的關(guān)系。
In general, acceleration is large at high frequencies and small at low frequencies. Displacement is just the opposite: small at high frequencies and large at low frequencies. Velocity tends to be more constant at different frequencies. The graph below shows the relationship of displacement and acceleration when velocity is held constant while varying the frequency range.
為了使該圖在信號強度方面有意義，必須添加傳感器靈敏度。通常，振動傳感器具有以下靈敏度：
? 速度 = 100mV/英寸/秒 = 3.94 mV/毫米/秒
? 加速度 = 100 毫伏/克
? 位移 = 200 mV/mil = 7.87 mV/μm
For this graph to have meaning in terms of signal strength, we have to add in the transducer sensitivity. Normally, vibration transducers have the following sensitivities:
? Velocity = 100mV/in/sec = 3.94 mV/mm/sec
? Acceleration = 100 mV/g
? Displacement = 200 mV/mil = 7.87 mV/μm
另請注意，上圖中的單位為 rms（均方根）；rms 是振動信號平均功率的度量（數(shù)學(xué)上，對于峰值幅度為 A 的正弦波，均方根幅度為 A/ ）。
Also, notice that in the above graph the units are in rms (root mean squared); rms is a measure of the average power of the vibration signal (mathematically, for a sine wave with a peak amplitude of A, the rms amplitude is A/ ).
下表顯示了不同頻率下 0.5 英寸/秒（12.7 毫米/秒）的速度常數(shù)值：
The table below shows a constant value of the velocity at 0.5 in/s (12.7 mm/s) at various frequencies:
對于下面的示例，假設(shè) 600 rpm、3000 rpm 和 30,000 rpm 時的恒定速度（0.5 英寸/秒）來說明差異。
For the examples below, let’s assume a constant velocity (0.5 in/s) at 600 rpm, 3000 rpm, and 30,000 rpm to illustrate the differences.
第 4 步：考慮傳感器所處的環(huán)境
Step 4: Consider the environment the transducer will be in
所選擇的傳感器需要能夠準(zhǔn)確測量其安裝的環(huán)境。要注意溫度和濕度的限制。傳感器會被淹沒嗎？是否需要危險區(qū)域批準(zhǔn)？
The transducer selected needs to be able to accurately measure the environment it is installed in. Pay attention to the temperature and humidity constraints. Is the transducer going to be submerged? Are hazardous area approvals needed?
第 5 步：選擇合適的傳感器
Step 5: Choose the right transducer
在考慮了機器類型、軸承類型、感興趣的頻率、傳感器對所測量信號的靈敏度以及環(huán)境之后，就可以選擇傳感器了。
After considering the machine type, the bearing type, the frequencies of interest, the transducer sensitivity for the signals you are measuring, and the environment you are ready to make a transducer selection.
對于配備滾動軸承、轉(zhuǎn)速為 1500 至 3600 rpm 的機器，速度傳感器已被證明是一種非常有效的狀態(tài)監(jiān)測工具。
For machines with rolling element bearings, rotating at 1500 to 3600 rpm, velocity sensors have proven to be a very effective condition monitoring tool.
對于往復(fù)式機器，由于它們能夠?qū)⒄駝訌那S箱傳遞到殼體，并且由于其速度較低，因此速度是衡量整體振動嚴(yán)重程度和機器狀況的更好的指標(biāo)。由于可能發(fā)生沖擊事件（閥門、曲軸、十字頭等），沖擊測量（通過連接到適當(dāng)監(jiān)視器的沖擊傳感器或加速度計）也是機器狀況的指示器。
For reciprocating machines, with their ability to transmit vibration from the crankcase to the casing, and due to their lower speeds, velocity is the best measure of overall vibration severity and machine condition. Due to possible impact events (valves, crankshaft, crosshead, etc.) impact measurement (via an impact transmitter or accelerometer connected to an appropriate monitor) is also an indicator of machine condition.
第 6 步：經(jīng)濟考慮
Step 6: Economic Considerations
選擇振動傳感器、振動發(fā)射器還是使用振動開關(guān)取決于客戶將投資回報率 (ROI)與人員安全風(fēng)險、維修成本以及導(dǎo)致失去機會成本 (LOC)的計劃外停機風(fēng)險等同起來。 ）旋轉(zhuǎn)或往復(fù)運動的機器可能會產(chǎn)生影響。 以下圖表有助于確定應(yīng)使用哪種類型的振動傳感器、發(fā)射器或開關(guān)。
The choice between a seismic sensor, a seismic transmitter, or the use of a vibration switch depends upon the Return on Investment (ROI) the customer equates with the risk of personnel safety, repair costs, and unscheduled downtime resulting in Lost Opportunity Cost (LOC) the rotating or reciprocating machine may affect. The following charts are useful in determining what type of vibration sensor, transmitter or switch should be used.
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