Question 1: What do you want to measure?

 

This may seem obvious, but think twice. What are you really measuring? In other words, what do you want to do? What do you hope to get? What are you going to do with the data? Acceleration sensors monitor vibration, providing raw vibration data, while vibration transmitters provide root mean square (RMS) values. Analyzing raw vibration data is useful because it contains information about all vibration signals, true peak amplitudes, and vibration frequencies. Because the RMS total or peak is a continuous 4-20 mA signal, it is very useful in systems such as PLC, DCS, SCADA and PI control systems. Some applications use both signals. By identifying the various signals required by your application, you can greatly narrow your search. Also, do you measure vibration using acceleration or velocity or displacement? Have you considered that some industrial sensors can output vibration and temperature at the same time? Finally, some field applications, such as vertical pumps, are best monitored for more than one shaft vibration. Does your field application require single, dual or triaxial measurements?

 

 Question 2: What is the amplitude?

 

The maximum amplitude or range of the measured vibration determines which range of sensors to use. Typical acceleration sensor sensitivity is 100 mV / g, standard applications (50g range) and 500 mV / g low frequency or low amplitude applications (10g range). 4-20 mA transmitters for general industrial applications typically use a range of 0-1 in / s or 0-2 in / s.

 

 Question 3: What is the vibration frequency?

 

For different excitation frequencies, the physical structure and dynamic system respond differently. Vibration sensors are no different. The properties of piezoelectric materials are like high-pass filters, so even the best piezoelectric sensors have a low frequency limit of about 0.2 Hz. As a single-degree-of-freedom dynamic system, the sensor has a natural resonance frequency. The signal is greatly amplified at the natural resonance frequency, resulting in a significant change in sensitivity, which is likely to be out of range. Most industrial accelerometers have single or dual RC filters to cancel the resonant frequency of the excitation. It is critical to choose the frequency range available for the sensor, which includes the frequencies you are interested in.

 

 Question 4: What is the ambient temperature?

 

For ICP acceleration sensors and 4-20mA transmitters, extremely high ambient temperatures pose a threat to internal electronics. The accelerometer in charge mode can be used at very high ambient temperatures. Instead of built-in electronics, it uses a remote charge amplifier. The charging mode acceleration sensor is equipped with an integrated hard-wired cable, which can be used in environments where the temperature exceeds 260 ° C, such as gas turbine vibration monitoring.

 

 Question 5: Will it be immersed in liquid?

 

Industrial acceleration sensors with integrated polyurethane cables can be permanently immersed in liquid. For high pressure applications, it is best to perform a one hour pressure test on the sensor. Completely submerged applications require integrated cables. Integral cables are also required in spraying, rather than completely submerging, such as machine cutting fluids.

 

 Question 6: Is it exposed to potentially harmful chemicals or debris?

 

Industrial acceleration sensors can be constructed using corrosion and chemical resistant stainless steel. In environments with hazardous chemicals, the sensor is considered to use PTFE corrosion-resistant connection cables. It is highly recommended to check the chemical compatibility chart for any suspicious chemical substance. For environments where chips can be accessed, the one-piece armored cable provides good protection.

 

 Question 7: Do you need to push out, biased, small links?

 

Ultimately, sensors need to be installed in the available space of the device. The shape of the sensor has little effect on its performance, but safety installation and maintenance operations on site need to be considered. The compact acceleration sensor with lock nut design can be fixed in any direction, but it is convenient when equipped with an integrated cable.

 

 Question 8: Do you use high-precision or low-cost sensors?

 

There are two main differences between low cost and high accuracy acceleration sensors. First, the accuracy units are usually fully calibrated, which refers to plotting sensitivity response measurements over the available frequency range. Low-cost accelerometers are single-point calibrations that perform sensitivity measurements at only one frequency. Second, high-accuracy acceleration sensors have strict tolerances such as sensitivity and frequency range in certain specifications.

 

 For example, a high-accuracy acceleration sensor has a nominal sensitivity of 100 mV / g ± 5% (95 mV / g to 105mV / g), while a low-cost acceleration sensor has a nominal sensitivity of 100 gates V / g ± 10% (90 mV / g to 110mV / g). Customers can set the calibration sensitivity of the sensor in the data acquisition system, so the low-cost sensor can also provide accurate and repeatable data. As for frequency, high-accuracy acceleration sensors usually have a maximum deviation of 5%, while low-cost sensors can provide a frequency range of 3 dB. Nevertheless, a low-cost sensor can provide excellent frequency response.

 

 Question 9: Do you need a special authentication code?

 

Both CSA and ATEX certified acceleration sensors and 4-20 mA transmitters can be used in hazardous areas. Compare the certification of the sensor to make sure it meets your needs.

 

 The answers to nine questions can greatly narrow your search to find the best solution for your application. Keep in mind that combined answers may be mutually exclusive, that is, solutions that meet each criterion do not exist. For example, certain models used in hazardous areas may not have ATEX certification. In addition, specialized field applications may have other considerations.