Triboelectric instrument with DC drift compensation

• US 5,448,172 A
• Filed: 05/05/1993
• Issued: 09/05/1995
• Est. Priority Date: 05/05/1993
• Status: Expired due to Fees

• Current Assignee: Oxford Instruments America Incorporated (Oxford Instruments PLC)
• Original Assignee: Auburn International, Inc. (Oxford Instruments PLC)
• Inventors: Swartzentruber, Ron L., Newton, Robert E., Dechene, Ronald L.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/057,611
• Time in Patent Office: 853 Days
• Field of Search: 324/454, 324/71.3, 324/71.1, 324/72.5, 324/72
• US Class Current: 324/454
• CPC Class Codes: G01F 1/64 by measuring electrical currents passing through the fluid flow; measuring electrical potential generated by the fluid flow, e.g. by electrochemical, contact or friction effects G01F1/58 takes precedence
• CPC Class Codes: G01N 27/60 by investigating electrostatic variables , e.g. electrographic flaw testing G01N27/007 takes precedence

Abstract

A microprocessor (48) controlled triboelectric instrument with probe fouling detection, zero offset adjustments and temperature compensation. The system programmability provides for enhanced operator control and operator monitoring wherein the system may be reprogrammed to advantage to reduce instrument down time.

Claims

1. A triboelectric instrument comprising:

(a) a probe;

(b) a converter means, wherein a triboelectric signal is received from the probe and converted to an amplified signal,

(b) a triaxial cable, with a center conductor, an inner shield, and an outer shield, connecting the probe to the converter,

(c) means for adjusting zero offset of said triboelectric signal,

(d) means for measuring and compensating for temperature drift of said instrument,

(e) means for isolating said probe from said converter means, means for introducing an AC signal into the converter means, where said converter produces an AC output signal, and wherein a change in said AC signal output indicates a faulty circuit component,

(f) means for grounding said signal and isolating said converter inputs wherein said converter output verifies an acceptable system zero, and

(g) means to drive said triaxial inner shield rendering said cable capacitance ineffective in distorting, or otherwise altering said amplified signal,

(h) processor means for controlling said instrument, wherein said temperature compensation and said zero offsets are measured, stored and controlled by said processor.

3. An instrument as defined in claim 1 further comprising:

a filter for detecting and separating the AC signal from the triboelectric signal, wherein said filter comprises electronic circuitry and software.

2. An improved triboelectric probe circuit comprising:

(a) a converter means, wherein a triboelectric signal is received from a probe and converted to an amplified output signal,

(b) means for introducing a detection signal into said converter wherein said detection signal is converted to an amplified output detection signal by utilizing substantially the same components as used to convert said triboelectric signal, wherein said amplification is dependent upon the degree of probe contamination,

(c) means for measuring said amplified output second signal wherein a change in the value of said converted output signal indicates a contaminated probe,

(d) a microprocessor for controlling the probe circuitry wherein the microprocessor has the ability to learn and remember the necessary amplifier corrections needed for variances in the ambient temperature and to correct for them in real time,

(e) means for determining thresholds of probe contamination for all available gain values,

(f) means for an operator unskilled in the art to enter setpoints for low and high emission alarms, alarm time delays, triboelectric signal time averaging for display of triboelectric signal, sensitivity, time and date, user defined password, user selection of the form of the analog output, time of the day for a routine Quality Assurance Report, and the means for the instrument to remember all of the above setpoints even in the case of power failure,

(g) means for notifying operator of said setpoints, various alarms, triboelectric signal value, correlated emissions rate, and system self checks with the use of a display readout or other.