Vibration measurement velocity transducers

Velocity transducers are electro-mechanical sensors designed to monitor casing, or relative, vibration. Unlike displacement probes, velocity transducers measure the rate of displacement rather than the distance of movement. Velocity is normally expressed in terms of inches per second (ips) peak, which is perhaps the best method of expressing the energy caused by machine vibration. Figure 43.22 is a schematic diagram of a velocity measurement device. 

Velocity transducers are an electro-mechanical sensor designed to monitor casing or relative vibration. Unlike the displacement probe, velocity transducers measure the rate of displacement not actual movement. Velocity data is... 

Dynaflect and Road Rater are vibrating load devices developed in the United States in the 1970s. They measure dynamic deflection while they are stationary, using a sinusoidal force. Unlike the Benkelman beam and semi-static devices, they are also capable of measuring the deflection basin since deflection is recorded by velocity transducers (usually five). Both devices comply with ASTM D 4695 (2008) and ASTM D 4602 (2008). 

In experiments to measure the properties (length, spacing and velocity) of dunes undergoing non-suspension flow [23], several sensors have been utilised, namely pressure transducers, vibration detectors and capacitance sensors. The first two sensors were off-the-shelf and the final one was developed for the purpose. In all cases, cross correlation was used between transducer pairs to measure velocity. The conclusion of the study was that the pressure transducers provided important data on the fluctuations in gas pressure as the dunes flowed and the vibration sensors were able to detect the waves passing - albeit with a considerable spatial filtering effect. The capacitance system was able to resolve the structure... 

Successful measurement of machine vibration requires more than a transducer randomly selected, installed, and a piece of wire to carry the signal to the analyzer. When the decision to monitor vibration is made, three choices of measurement are available (1) displacement, (2) velocity, and... 

Technically, peak-to-peak values should be used in conjunction with actual shaft-displacement data, which are measured with a proximity or displacement transducer. Peak-to-peak terms should not be used for vibration data acquired using either relative vibration data from bearing caps or when using a velocity or acceleration transducer. The only exception is when vibration levels must be compared to vibration-severity charts based on peak-to-peak values. 

Figure 3.15 Shock-tube arrangement of Kiefer and Lutz [129], utilizing laser-beam deflection, for study of vibrational relaxation in D2. Tx and T2 are collimating telescopes, Wx and W2 are windows (P) designates pressure transducers for measurement of shock velocity.

The complex mechanical impedance can be obtained by measuring force, velocity, and their phase difference using probes or pickups attached to the transducer at suitable points [144], This method is very convenient with solids [52] (sometimes the most accurate), but not with liquids, although in this case it can be a convenient method of checking the performance of a transducer. The output from an accelerometer or strain-sensitive pickup gives information on resonant frequency and vibrational amplitude. However subsequent correlation with the power transmitted to the sonicated medium is not straightforward. 

Detailed direct experimental evidence for the frictional behavior during the slip part of a stick-slip cycle is found in the work reported by Ko and Brockley [17]. The rider and its elastic coupling were fitted with the following transducer devices (a) a strain gage to measure the displacement of the rider from its null position (b) an electromagnetic transducer to measure the velocity of the rider during vibration or transport and (c) an accelerometer to measure the acceleration of the rider. The data obtained with this instrumentation were used in the equation for stick-slip (c(S. Eqn 8-18) ... 

For the measurement and assessment of the effects of ground vibrations due to blasting on buildings (see DIN 4150, Part 3), the vibration pickups (transducers) for the three mutually perpendicular velocity components are installed in or on the foundation of the building or otherwise in the wall as close above ground level as possible and preferably on the side facing the blasting site. 

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