Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Measurement of Impedances Under Dynamic Pulse Conditions

IP.com Disclosure Number: IPCOM000093930D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 4 page(s) / 58K

Publishing Venue

IBM

Related People

Chambers, GR: AUTHOR [+2]

Abstract

This measuring technique enables the reactive components of mixed impedances to be measured oscillographically. Such measurements are made under dynamic pulse conditions without critical limitations of pulse amplitude, frequency or rise time.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 42% of the total text.

Page 1 of 4

Measurement of Impedances Under Dynamic Pulse Conditions

This measuring technique enables the reactive components of mixed impedances to be measured oscillographically. Such measurements are made under dynamic pulse conditions without critical limitations of pulse amplitude, frequency or rise time.

A sampling oscilloscope in drawing A is equipped with an automatic area integrator. The latter integrates the area beneath a curve trace between one or more sets of time limits selected by the operator. The oscilloscope has two input channels A and B. Channel A receives a current signal or a voltage signal from the unknown impedance, depending upon whether the impedance primarily contains a capacitive reactance or inductive reactance. The capacitive or inductive nature current waveshapes which it produces when it is pulsed. If the impedance is primarily capacitive, it is supplied periodically with a voltage pulse of predetermined shape. The resulting current wave is sensed by a current probe. If the impedance is primarily inductive, it is supplied periodically with a current pulse of predetermined shape. The resulting voltage wave is sensed by a voltage probe. The pulse amplitude, frequency and rise time are not critical in this system, so long as the pulses are uniform.

It is assumed that the resistive component of the impedance is measured either by a conventional DC Ohm's-law method, where possible, or by simple deduction from the measured impedance and reactance values. With regard to measuring the reactive component of the impedance, this is considered in four categories, each illustrated by a separate drawing.

In drawing B there is the type of current waveshape which is produced by the parallel combination of resistance R and capacitance C in response to an applied voltage pulse having a waveshape of the indicated type. These waveshape representations are idealized for the purpose of illustration. To measure the unknown capacitance C, it is necessary to determine the ratio between the applied voltage v and the resultant charge on C, the charge being measured in ampere-seconds. In this instance the magnitude of the charge on C cannot be determined directly from the total current flow. This is because the total current i(T) contains a component i(R) which does not flow through the capacitor C. Hence, the integral of i(C)dt cannot be measured directly. Instead, an indirect method of measuring the integral of i(C)dt is employed as illustrated.

This is accomplished by first integrating the area in ampere seconds beneath the current wave during the charging period while the pulse is rising. Then there is integrated the area in ampere seconds beneath the current wave during the discharge period, while the pulse is falling. Finally the latter area is subtracted from the former area to obtain twice the integral of i(C)dt during each transient period. This relationship can be deducted from the fact that during the charging period the curren...