Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1988-07-21
1990-08-21
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
73304C, 324611, 324671, G01R 2726
Patent
active
049509985
ABSTRACT:
A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.
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Robertshaw Controls Company, Product Specification Model 157A, Level-Tel Transmitter Model 157A.
Kramer Jonathan L.
Petersen Steven R.
Shauger, Jr. Herbert A.
Drexelbrook Controls, Inc.
Eisenzopf Reinhard J.
Mueller Robert W.
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