Abstract
This paper presents some observations on the dynamic behaviour of a chain of typical instrument elements, for example, a pressure measuring system consisting of a transducer-amplifier-galvanometer (or oscilloscope) chain.
The approach adopted is by way of two approximate formulae which have been found to describe the dynamic characteristics of pulse amplifiers. These formulae are then applied to a linear second-order system which is shown to represent many transducer and galvanometer systems.
The bounds within which the formulae apply to such systems are easily found from the transient response of the second-order system model which is readily available in analytical form.
The dynamic input function used is not a true step function but an ‘imperfect step function’ having a finite, but small, input rise time. This input is likened to the output of a preceding instrument element, in response to a true step input, and thus the overall rise time of the two elements is obtained.
Apart from its use in the verification of the two formulae, the imperfect step function response of transducers and galvanometers is important in its own right, and thus is discussed in some detail in relation to some recently published papers.
As this work proceeded, information was required on such instrument characteristics as rise time, bandwidth, and damping factor. Published data on such topics, especially for the majority of pressure transducers, was found to be sparse and thus the topics are discussed at some length and new information is presented on transducer damping factors.
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