US3582767A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus having an integrated amplifiers for monitoring the conductivity of solutions
Assignee: Lubrizol Corp
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Filing: 1969-01-31
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Granted: 1971-06-01
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Expires: 1989-01-31
Abstract
Abstract Apparatus for monitoring the conductivity of solutions over a broad range consisting of an electronic circuit including a test electrode which is adapted for immersion in the solution and through which an AC current is passed. The electrode forms part of a bridge circuit for developing an error voltage having a phase and amplitude related to the conductivity of the solution. A synchronous chopper converts the error voltage to an analog DC level for application to an integrated circuit operational amplifier. The amplifier receives as a second input a temperature compensated voltage and a variable feedback resistor connected between the output of the amplifier and the second input serves to vary the gain of the amplifier and adjust the span of conductivity readings. A volt meter is connected to the output of the amplifier to provide a continuous indication of conductivity levels and a further voltage sensing circuit compares the output voltage of the amplifier with a set point level to provide a visual indication of preset conductivity levels and a switching function for external control circuitry.
Inventors
- 👤 Thomas W Brum
- 👤 Frank D Cochran
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 06:18
CPC Classifications
G; G05; G05D; G05D21/00; G05D21/02; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/045
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
166 words
A meter for indicating the conductivity of solutions, comprising a pair of electrodes adapted to be submerged in the solution under test, means for passing a current through said electrodes and thus through the solution for developing a voltage across said electrodes proportional to the conductivity of the solution, an integrated circuit amplifier having first and second input terminals, a bridge circuit for connecting said electrodes to said amplifier for producing an output voltage as a function of the voltage developed across said electrodes, said electrodes being connected as one leg of said bridge circuit, the output of the latter being operatively connected to said first input terminal of said Amplifier, a temperature compensated voltage reference source connected to said second input terminal, a variable feedback element connected between the output of said amplifier and said second input terminal for adjusting the gain of said amplifier, and means connected to said amplifier for providing an indication of the voltage realized at the output of said amplifier.
Claim 2
Dependent Claim
166 words
A meter for indicating the conductivity of solutions, comprising a pair of electrodes adapted to be submerged in the solution under test, means for passing a current through said electrodes and thus through the solution for developing a voltage across said electrodes proportional to the conductivity of the solution, an integrated circuit amplifier having first and second input terminals, a bridge circuit for connecting said electrodes to said amplifier for producing an output voltage as a function of the voltage developed across said electrodes, said electrodes being connected as one leg of said bridge circuit, the output of the latter being operatively connected to said first input terminal of said Amplifier, a temperature compensated voltage reference source connected to said second input terminal, a variable feedback element connected between the output of said amplifier and said second input terminal for adjusting the gain of said amplifier, and means connected to said amplifier for providing an indication of the voltage realized at the output of said amplifier.
Claim 3
Dependent Claim
61 words
The meter as set forth in claim 1 wherein said indication means comprises a voltmeter connected to the output of said amplifier for providing a continuous indication of the conductivity of solutions under test, and said bridge circuit comprises an adjustable element for varying the proportionality of voltage from said electrodes, thereby to modify the span of indication of said voltmeter.
Claim 4
Dependent Claim
45 words
The meter as set forth in claim 2 further including an adjustable reference voltage source, a comparator connected to the output of said amplifier and said adjustable reference voltage source, and a relay actuated by the output of said comparator at such reference voltage level.
Claim 5
Dependent Claim
34 words
The meter as set forth in claim 3 further including a pair of indicator lamps connected to alternately energized contacts of said relay for providing a visual indication of the state of said comparator.
Claim 6
Dependent Claim
72 words
The meter as set forth in claim 4 wherein said comparator is a second integrated circuit amplifier connected in an open loop mode, said adjustable reference voltage source is connected to the inverting input of said second amplifier and the output of said first amplifier is connected to the noninverting input, whereby when the noninverting input becomes more positive than the inverting input, said second amplifier will switch to a conducting state.
Claim 7
Dependent Claim
181 words
Monitoring apparatus for measuring the conductivity of fluids comprising a pair of electrodes adapted to be immersed in the fluid under measurement, a bridge circuit having resistors in three legs, said electrodes being connected as the fourth leg of said bridge circuit, a transformer energized from a source of AC power, the secondary winding of said transformer being connected to energize said bridge circuit and develop an AC error voltage of phase and amplitude related to the conductivity of the fluid under measurement, a demodulator for converting the error voltage to a proportional DC level, an amplifier having first and second input terminals and an output terminal, the DC level of said demodulator being connected to the first input terminal, a temperature compensated voltage source connected to the second input terminal, a feedback element connected between the output and second input terminals, and a meter connected to the output terminal to provide indications of the conductivity of the fluid, said feedback element being adjustable to vary the gain of said amplifier to provide various ranges of conductivity indications at said meter.
Claim 8
Dependent Claim
181 words
Monitoring apparatus for measuring the conductivity of fluids comprising a pair of electrodes adapted to be immersed in the fluid under measurement, a bridge circuit having resistors in three legs, said electrodes being connected as the fourth leg of said bridge circuit, a transformer energized from a source of AC power, the secondary winding of said transformer being connected to energize said bridge circuit and develop an AC error voltage of phase and amplitude related to the conductivity of the fluid under measurement, a demodulator for converting the error voltage to a proportional DC level, an amplifier having first and second input terminals and an output terminal, the DC level of said demodulator being connected to the first input terminal, a temperature compensated voltage source connected to the second input terminal, a feedback element connected between the output and second input terminals, and a meter connected to the output terminal to provide indications of the conductivity of the fluid, said feedback element being adjustable to vary the gain of said amplifier to provide various ranges of conductivity indications at said meter.
Claim 9
Dependent Claim
35 words
Apparatus as set forth in claim 6 wherein said demodulator is a chopper synchronized to the AC power source, said amplifier is an integrated circuit operational amplifier, and said feedback element is a variable resistor.
Claim 10
Dependent Claim
41 words
Apparatus as set forth in claim 7 wherein one of the resistors in said bridge circuit is a variable resistor for adjusting the error voltage from said bridge circuit, said variable resistor thereby providing a zero-set function for the monitoring apparatus.
Claim 11
Dependent Claim
92 words
Apparatus as set forth in claim 8 further including a second operational amplifier connected in open loop mode, the output of said first amplifier being connected as one input to said second amplifier, means for applying a set point voltage as the second input of said second amplifier, a transistor amplifier connected to the output of said second amplifier, and a relay energized by said transistor amplifier when the output of said first amplifier exceeds the set point voltage for providing a control function dependent upon the measured conductivity of the fluid.
Claim 12
Dependent Claim
51 words
Apparatus as set forth in claim 9 further including a pair of indicator lAmps connected to normally open and normally closed contacts of said relay, and means for energizing such contacts thereby to alternately illuminate said lamps at conductivity levels above or below that level corresponding to the set point voltage.
References Cited (Backward Citations)
US3493857A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-31 | 1974-11-30 | 1975-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-31 | 1978-11-30 | 1979-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-31 | 1982-11-30 | 1983-06-01 | $7700.00 | Window Closed / Lapsed |