Automatic control and detector for three-terminal resistance measurement

Patent · Tue Oct 26 04:00:00 EDT 1976

OSTI ID:7311085

Fasching, G E

A device is provided for automatic control and detection in a three-terminal resistance measuring instrument. The invention is useful for the rapid measurement of the resistivity of various bulk material with a three-terminal electrode system. The device maintains the current through the sample at a fixed level while measuring the voltage across the sample to detect the sample resistance. The three-electrode system contacts the bulk material and the current through the sample is held constant by means of a control circuit connected to a first of the three electrodes and works in conjunction with a feedback controlled amplifier to null the voltage between the first electrode and a second electrode connected to the controlled amplifier output. An ac oscillator provides a source of sinusoidal reference voltage of the frequency at which the measurement is to be executed. Synchronous reference pulses for synchronous detectors in the control circuit and an output detector circuit are provided by a synchronous pulse generator. The output of the controlled amplifier circuit is sampled by an output detector circuit to develop at an output terminal thereof a dc voltage which is proportional to the sample resistance R. The sample resistance is that segment of the sample between the area of the first electrode and the third electrode, which is connected to ground potential. 6 claims, 10 figures.

• Assignee: Energy Research and Development Administration
• Patent Number(s): US 3988669
• OSTI ID: 7311085
• Country of Publication: United States
• Language: English

Related Subjects

440400* -- Well Logging Instrumentation
47 OTHER INSTRUMENTATION
CONTROL SYSTEMS
ELECTRIC CONDUCTIVITY
ELECTRIC LOGGING
ELECTRICAL PROPERTIES
ELECTRODES
ELECTRONIC CIRCUITS
ELECTRONIC EQUIPMENT
EQUIPMENT
FEEDBACK
FUNCTION GENERATORS
MEASURING INSTRUMENTS
MEASURING METHODS
PHYSICAL PROPERTIES
PULSE GENERATORS
RESISTIVITY LOGGING
WELL LOGGING