The output signal and the high frequency harmonic wave are superimposed, which is generally caused by the resonant frequency of the sensor. Choose a sensor with a higher resonant frequency
1. The measurement range is reduced due to the decrease of the power supply voltage. Replace the battery or correct the power supply voltage.
2. The bias voltage caused by the difference between the ambient temperature and the room temperature exceeds the specified range, and a sensor with a stable bias voltage can be used.
3. Due to the non-linearity of the sensor, a sensor with a large range can be used
4. In the long-distance signal transmission, the constant current of the constant current source voltage is not large enough, the correct voltage and constant current source current can be selected according to the signal frequency amplitude
In a non-room temperature environment, the sensitivity deviation caused by the excessive temperature response coefficient of the piezoelectric material, a sensor with a small temperature response coefficient deviation can be selected.
1. The insulation resistance of the sensitive core of the piezoelectric sensor decreases, and the sensor can be baked within its use temperature range, and the sensitivity can rise, but generally it will drop again.
2. The piezoelectric coefficient of the sensor's sensitive core is attenuated, and the sensor needs to be recalibrated.
1. The built-in circuit of the sensor is not working properly.
2. The bias voltage drifts due to the unstable change of the ambient temperature, so install a heat insulation pad or a sheath.
It is caused by the cable connection or the disconnection of the internal wiring of the sensor. Replace the cable or sensor.
Sensors are usually composed of sensitive elements and conversion elements. They are a general term for devices or devices that can detect the specified measured and convert them into usable output signals according to certain rules.
When the output of the sensor is a specified standard signal, it is a transmitter. The device that converts a physical signal into an electrical signal is called a sensor, and an instrument that converts a non-standard electrical signal into a standard electrical signal is called a transmitter.
The advantage of voltage signal input is: the signal is easy to handle (you can test the "disconnection"), the disadvantage is: the long-distance transmission signal is attenuated;
The advantage of current signal input is that the voltage at the input terminal can be transmitted over a long distance without attenuation. The disadvantage is: the signal needs to be converted, which is slightly troublesome.
Both types of input have interference problems, and both need to be careful to solve the noise problem.
Considering the main indicators of the static characteristics of the sensor, select a sensor with high linearity, low hysteresis, good repeatability, strong resolution, high stability, and high anti-interference stability. Considering the dynamic performance, the selected sensor should be able to follow the rapid changes of the input well, have a short transient response time or should have a wide frequency response characteristic.
Question 1: What do you want to measure?
This may seem obvious, but please 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? The acceleration sensor can monitor vibration and provide raw vibration data, while the vibration transmitter provides the root mean square (RMS) value. Analyzing raw vibration data is useful because it contains information about all vibration signals, the true peak amplitude and vibration frequency. Because the RMS total value or peak value is a continuous 4-20 mA signal, it is very useful in PLC, DCS, SCADA systems and PI control systems. Some applications use both signals at the same time. By determining the various signals required by the application, the search can be greatly narrowed. In addition, do you use acceleration or velocity or displacement to measure vibration? Have you considered that some industrial sensors can output vibration and temperature at the same time? Later, some field applications, such as vertical pumps, are better to monitor vibration of more than one shaft. Does your field application require single-axis, dual-axis or three-axis measurement?
Question 2: How big is the amplitude?
The amplitude or range of the measured vibration determines which range of sensors to use. A typical acceleration sensor has a sensitivity of 100 mV/g, for standard applications (50g range) and 500 mV/g for low-frequency or low-amplitude applications (10g range). 4-20 mA transmitters for general industrial applications usually use the 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 react differently. The vibration sensor is no different. The properties of piezoelectric materials are like high-pass filters. Therefore, even a good piezoelectric sensor has 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 exceed the range. Most industrial accelerometers have single or dual RC filters to cancel the excited resonance frequency. It is critical to select the frequency range available for the sensor, which includes the frequency 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 accelerating sensor in charging mode can be used in very high ambient temperatures. It does not have built-in electronics, but 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 submerged in liquid?
Industrial accelerometers with integrated polyurethane cables can be immersed in liquid installation. For high-pressure applications, good sensors are subjected to a one-hour pressure test. Fully submerged applications require integrated cables. An integrated cable is also required in applications where it is sprayed rather than completely submerged, such as machine tool cutting fluid.
Question 6: Will it be exposed to potentially harmful chemicals or debris?
Industrial acceleration sensors can be constructed using corrosion-resistant and chemical-resistant stainless steel. In the environment of harmful chemical substances, the sensor considers the use of PTFE corrosion-resistant connecting cables. It is strongly recommended to check the chemical compatibility chart of any suspicious chemical substances. For the environment that can come into contact with chips, the integrated armored cable can provide good protection.
Question 7: Do you need top-out, out-of-pocket, and small links?
Terminal sensors need to be installed in the available space of the device. The shape of the sensor has little effect on its performance, but on-site safe installation and maintenance operations need to be considered. The compact acceleration sensor with lock nut design can be fixed in any direction, but it is very 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-precision acceleration sensors. First, the accuracy unit is usually fully calibrated, which refers to the sensitivity response measurement plot within the available frequency range. The low-cost accelerometer is calibrated at a single point and only measures the sensitivity at one frequency. Second, high-precision acceleration sensors have strict tolerances such as sensitivity and frequency range in certain specifications.
For example, a high-precision acceleration sensor has a nominal sensitivity of 100 mV/g ± 5% (95 mV/g to 105 mV/g), while a low-cost acceleration sensor has a nominal sensitivity of 100 mV/g ± 10% (90 mV/g). To 110mV/g). Customers can set the calibration sensitivity of the sensor in the data acquisition system, so that low-cost sensors can also provide accurate and repeatable data. As for frequency, high-precision acceleration sensors usually have a 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?
Acceleration sensors and 4-20 mA transmitters certified by CSA and ATEX can be used in hazardous areas. Compare the certification of the sensor to make sure it meets your needs.