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6.10 Force Measurements: Machinery Condition Monitoring: Principles and Practices

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phoneme79

This document discusses different types of transducers used to measure various mechanical properties including acceleration, force, and rotational speed. It describes how accelerometers use charge-to-voltage amplifiers to measure acceleration in mV/ms-2 and may require calibration in the field. It also explains that piezoelectric crystals are commonly used in force transducers and generate a proportional AC signal under tensile and compressive forces. The document outlines that impedance heads can simultaneously measure acceleration and force using dual piezoelectric crystals and a dual-channel charge amplifier.

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6.10 Force Measurements: Machinery Condition Monitoring: Principles and Practices

Uploaded by

phoneme79
27 views1 page
This document discusses different types of transducers used to measure various mechanical properties including acceleration, force, and rotational speed. It describes how accelerometers use charge-to-voltage amplifiers to measure acceleration in mV/ms-2 and may require calibration in the field. It also explains that piezoelectric crystals are commonly used in force transducers and generate a proportional AC signal under tensile and compressive forces. The document outlines that impedance heads can simultaneously measure acceleration and force using dual piezoelectric crystals and a dual-channel charge amplifier.

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force measurement

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Force Measurement

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This document discusses different types of transducers used to measure various mechanical properties including acceleration, force, and rotational speed. It describes how accelerometers use charge-to-voltage amplifiers to measure acceleration in mV/ms-2 and may require calibration in the field. It also explains that piezoelectric crystals are commonly used in force transducers and generate a proportional AC signal under tensile and compressive forces. The document outlines that impedance heads can simultaneously measure acceleration and force using dual piezoelectric crystals and a dual-channel charge amplifier.

Copyright:

© All Rights Reserved
Download as PDF, TXT or read online from Scribd
Download as pdf or txt
27 views1 page

6.10 Force Measurements: Machinery Condition Monitoring: Principles and Practices

Uploaded by

phoneme79
This document discusses different types of transducers used to measure various mechanical properties including acceleration, force, and rotational speed. It describes how accelerometers use charge-to-voltage amplifiers to measure acceleration in mV/ms-2 and may require calibration in the field. It also explains that piezoelectric crystals are commonly used in force transducers and generate a proportional AC signal under tensile and compressive forces. The document outlines that impedance heads can simultaneously measure acceleration and force using dual piezoelectric crystals and a dual-channel charge amplifier.

Copyright:

© All Rights Reserved
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74 Machinery Condition Monitoring: Principles and Practices

The charge sensitivity of the accelerometers are usually given in pC/ms−2


and after a suitable voltage conversion by the charge-to-voltage amplifier, the
output is provided as mV/ms−2. These amplifiers have a few other features,
like signal cable fault detection, signal overload detection, filters to set the
upper and lower frequencies of measurement, amplification to a certain gain,
and an integrator for converting the measured acceleration to either voltage
or displacement. In the field, due to use of long cables, there may be a loss of
signal strength and it is usually a good practice to use an in situ handheld
calibrator to calibrate accelerometers.

6.10  Force Measurements


In many applications, particularly during component testing, the measure-
ment of dynamic force is required. In such applications, the piezoelectric
crystals are once again used. These materials are usually given a precom-
pression and held between discs in a sealed unit. When this transducer is
subjected to both tensile and compressive forces, it produces a proportional
AC signal. These force transducers also require a charge amplifier for signal
condition. In tool condition monitoring for measuring cutting forces, piezo-
based cutting force dynamometers are extensively used. The typical range of
such force transducers are from −12 kN to +10 kN.
For very large force measurements, load cells with strain gauges are used.
However, such strain gauge load cells require an additional bridge circuit
(like a Wheatstone bridge) for measuring the strains induced by mechani-
cal load. The piezoelectric-based force transducers have a better frequency
response than the strain gauge type of load cells.
A transducer that has both an accelerometer and a force measuring gauge
is known as an impedance head. Such a transducer has two sets of piezo-
electric crystals stacked next to each other in a sealed casing. An impedance
head is convenient to measure the driving point impedance of the DUT. This
is usually attached on top of the stinger from an electrodynamic shaker.
The  impedance head can have charge-type transducers, and would thus
need a dual-channel charge-type amplifier.

6.11  Rotational Speed


Rotational speed is a very important parameter to be measured in the case
of rotating machines, since the dynamic motions of machines are related to
their rotational speed. There are many transducers available for measurement

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