Agilent 1952-07 free download

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HEWLETT' PACKARD JOURNAL T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S VOL. 3 No. 11 PUBLISHED BY THE HEWLETT-PACKARD COMPANY, 395 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY, 1952 A Novel Impedance -Measuring System Using Standard -hp- Instruments WHEN an impedance is fed from a con will give even wider ranges of measurements stant-current source, the voltage than those listed above. across the impedance is a function of the The basic set-up for the measurements is magnitude of the impedance. indicated in Fig. 1. The -hp- Model 200 This basic relation will permit a combina audio oscillator is converted to a constant- tion of two standard -hp- instruments to be current source by insertion of a 1 -megohm used to measure extremely wide ranges of resistance in series with the generator output L and C as well as moderate ranges of R and terminals. The voltage across an unknown Z. C's from 800 microfarads to a few micro- impedance connected into the circuit will microfarads, L's from 200 henrys to 100 mi- then be proportional to the magnitude of crohenrys, and R'sandZ's from 30,000 ohms the unknown impedance. to a few ohms can be measured. A feature As part of the set-up procedure, the oscil of the system is that, in general, the meas lator output voltage is adjusted by the panel ured values can be read directly. controls to be 10 volts. Since the circuit im The two instruments required for the pedance is 1 megohm, a generator voltage measurements are an oscillator and a sensi of 10 volts will cause a constant current of tive voltmeter. Several different combina 10.0 microamperes to flow through the un tions of -hp- oscillators and v