发明名称 |
Continuous condition sensing system |
摘要 |
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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申请公布号 |
US4950998(A) |
申请公布日期 |
1990.08.21 |
申请号 |
US19880222498 |
申请日期 |
1988.07.21 |
申请人 |
DREXELBROOK CONTROLS, INC. |
发明人 |
KRAMER, JONATHAN L.;PETERSEN, STEVEN R.;SHAUGER, JR., HERBERT A. |
分类号 |
G01R27/26 |
主分类号 |
G01R27/26 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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