# Limitations of Using DAQ Cards for Absolute Vibration Measurement in Hydraulic Machines
###### Abstract  
Vibration measurements are a frequently used tool in technical issues. They are widely used in operation and for testing irregularities in the operation of machines and devices, including hydraulic machines (turbines, pumps, and pump turbines). This article considers the possibility of using measurement cards to measure the absolute vibrations of hydraulic machines. Basic information related to vibrations and their measurement, as well as requirements specified in standards related to vibrations of hydraulic machines, are presented. Then, six measurement cards are tested, and the possibility of their use in vibration measurements of hydraulic machines using accelerometers is analyzed.  
vibrations; vibration measurements; hydraulic machines; diagnostics; operation of hydraulic machines; DAQ cards +
Footnote †: journal: Applied sciences  
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lower costs associated with vibration measurements is evident in the search for low-budget alternatives [22; 23].  
Regardless of the underlying rationale, should developing a novel vibration measurement system arise, it would appear reasonable to consider utilizing existing data acquisition cards for this purpose. Such an approach could prove cost-effective, reduce the time required to build the system, and facilitate the creation of the necessary vibration measurement and analysis software.  
Despite the rich literature related to vibration measurements, there are no deeper analyses regarding the possibilities of using typical DAQ cards to record signals from accelerometers, especially when measuring the vibrations of hydraulic machines. There is literature available on the use of DAQ devices (National Instruments Inc., Austin, TX, USA) for absolute vibration measurements. However, it concerns issues other than those presented in this article. As mentioned above, they are concerned with reducing the costs of DAQ devices [22; 23; 24], structural health monitoring [24; 25], high-frequency condition monitoring [26], signal conditioning and processing systems [27], and wireless vibration measurement devices [28]. However, there is no detailed information on the use of DAQ devices for absolute vibration measurements of hydraulic machines. Only general information can be found, e.g., related to noise [29]. General information about low-frequency vibration measurement systems can also be found in the resources of accelerometer manufacturers. The lack of appropriate research and literature means that absolute vibration measurements of hydraulic machines are often performed incorrectly. The author has often encountered a lack of appropriate knowledge. This lack is visible in suppliers of measuring devices, as well as in those who perform measurements. The aim of the paper is to fill this gap. Therefore, this article focuses on the possibilities and limitations resulting from the use of DAQ devices in relation to the measurement of absolute vibrations of hydraulic machines (hydro sets, pump sets), performed using piezoelectric accelerometers. It can be concluded that the information presented below will allow for a better understanding of the requirements placed on devices for measuring the vibrations of hydraulic machines. It will also reduce the number of errors made when selecting measuring devices. As a result, it will increase the usefulness and reliability of vibration analysis measurements.  
Despite the fact that the topic concerns measurement cards, the observations included here can also be extended to signal processing systems of other devices used to measure vibrations.