加速度计和速度传感器的区别(中英文)
要确定是否应该使用加速度计或速度传感器,首先重要的是要了解它们之间的区别。加速度计是一种机械装置,用于测量结构或机器运动或加速度的变化。然后这种运动被转换成可以测量的电信号。通常,加速度计可用于测量冲击力或机器的振动。
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.
速度传感器不是测量绝对位置,而是使用振动装置来测量位置随着时间的变化。然后它计算这个变化以确定速度。
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.
为了更好地确定哪种测量形式最适合具体情况,请阅读以下内容以确定是应该使用加速度计还是速度传感器。
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:确定要测量的内容
Step 1: Determine what you want to measure
一般经验如下:
The general rules of thumb are as follows:
• 如果转子可以相对于外壳移动,对实际轴运动,必须使用接近探头。
If the rotor can move relative to the casing, and you are interested in actual shaft motion, you must use a proximity probe.
• 对套管运动,应该使用振动传感器(速度传感器或加速度计);选择使用哪种传感器应考虑传感器在不同频率下提供的信号强度。
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.
• 如果因为某些应用选择加速度计,信号强度可能非常小(小于几毫伏),并且很容易被系统中的噪声淹没,从而很难将信号与噪声分开。
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.
• 尽管压电速度传感器只是带有内部积分器的加速度计,但它可以为监视器中的集成提供更好的结果。这也是因为传感器发出的信号强度(以 mV 为单位)相对于噪声强度(以 mV 为单位)。
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).
• 在低速和中速旋转时,压电速度传感器通常是一个不错的选择;在低转速下,加速度计通常是一个糟糕的选择,但在中高转速下是一个不错的选择。
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.
请记住,对于油膜轴承机器,通常使用轴观察接近探头,但往复式机器除外。尽管往复式机器具有支撑曲轴的油膜轴承,但机器非常坚硬,曲轴和外壳之间几乎没有相对运动,因此在这种情况下,安装在外壳上的传感器将是更好的应用。对于滚动轴承机器,转子和外壳之间的相对运动非常小,因此安装在外壳上的传感器通常是更好的应用。一个例外是具有非常大的滚动轴承的缓慢移动的转子;在这种情况下,由于轴运动缓慢且滚动轴承可能磨损,接近探头可能是监控机器状况更好的传感器。
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:确定频率
Step 2: Determine the frequencies of interest
• 大多数与转子相关的故障(不平衡、不对中、金属与金属摩擦、不稳定、轴裂纹、保持架缺陷等)出现在 1/4X 到 3X 之间(1X = 转子速度,以每分钟转数 (rpm)、cps、或赫兹)。
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).
• 大多数滚动轴承缺陷发生在外圈滚珠通行频率的 1 至 6 倍范围内(简单地说,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).
• 较高的振动频率可能是由于叶片通过率、齿轮啮合、BPFO 频率的谐波以及其他振动谐波(叶片通过率 = # 叶片 x 转子速度 (1X),齿轮啮合频率 = # 齿轮齿数 x 转子速度 (1X) ),谐波是振动波形不是完美正弦波时产生的基本强迫频率的倍数)。
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).
• 撞击事件是激发高阶频率的宽带能量来源。
Impact events are a source of broadband energy that excites higher-order frequencies.
示例:离心泵,带有七个叶片叶轮,运行速度为 3000 rpm,带有滚动元件轴承,每个轴承有 10 个滚动元件,需要监控。频率为:
1X = 3000 rpm = 50 cps = 50 Hz
1/4X 至 3X = 12.5 至 150 cps = 12.5 至 150 Hz,对于与转子相关的故障
BPFO 大约 = 10 个元件 x 50 cps / 2 = 250 cps = 250 Hz
BPFO 的 1 至 6 倍 = 250 至 1500 cps = 250 至 1500 Hz,用于轴承相关故障 叶片
通过率 = 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
人们会选择一种安装在套管上的传感器,该传感器至少可以测量12.5 赫兹至 1500 赫兹。
One would select a casing-mounted transducer that could measure at least 12.5 Hz to 1500 Hz.
第 3 步:确定所需的套管传感器灵敏度
Step 3: Determine the required casing transducer sensitivity
一般来说,高频时加速大,低频时加速小。位移正好相反:高频时位移小,低频时位移大。不同频率下的速度往往更加恒定。下图显示了当速度保持恒定而改变频率范围时位移和加速度的关系。
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.
为了使该图在信号强度方面有意义,必须添加传感器灵敏度。通常,振动传感器具有以下灵敏度:
• 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
另请注意,上图中的单位为 rms(均方根);rms 是振动信号平均功率的度量(数学上,对于峰值幅度为 A 的正弦波,均方根幅度为 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/ ).
下表显示了不同频率下 0.5 英寸/秒(12.7 毫米/秒)的速度常数值:
The table below shows a constant value of the velocity at 0.5 in/s (12.7 mm/s) at various frequencies:
对于下面的示例,假设 600 rpm、3000 rpm 和 30,000 rpm 时的恒定速度(0.5 英寸/秒)来说明差异。
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:考虑传感器所处的环境
Step 4: Consider the environment the transducer will be in
所选择的传感器需要能够准确测量其安装的环境。要注意温度和湿度的限制。传感器会被淹没吗?是否需要危险区域批准?
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:选择合适的传感器
Step 5: Choose the right transducer
在考虑了机器类型、轴承类型、感兴趣的频率、传感器对所测量信号的灵敏度以及环境之后,就可以选择传感器了。
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.
对于配备滚动轴承、转速为 1500 至 3600 rpm 的机器,速度传感器已被证明是一种非常有效的状态监测工具。
For machines with rolling element bearings, rotating at 1500 to 3600 rpm, velocity sensors have proven to be a very effective condition monitoring tool.
对于往复式机器,由于它们能够将振动从曲轴箱传递到壳体,并且由于其速度较低,因此速度是衡量整体振动严重程度和机器状况的更好的指标。由于可能发生冲击事件(阀门、曲轴、十字头等),冲击测量(通过连接到适当监视器的冲击传感器或加速度计)也是机器状况的指示器。
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:经济考虑
Step 6: Economic Considerations
选择振动传感器、振动发射器还是使用振动开关取决于客户将投资回报率 (ROI)与人员安全风险、维修成本以及导致失去机会成本 (LOC)的计划外停机风险等同起来。 )旋转或往复运动的机器可能会产生影响。 以下图表有助于确定应使用哪种类型的振动传感器、发射器或开关。
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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