US 10,845,394 B2Granted

Null detector devices and systems employing same

AssigneeGuildline Instruments Limited

InventorsTomasz Barczyk, Richard Timmons, Mark Evans

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Abstract

Within electrical test equipment systems comparator bridges are employed to provide the required dynamic range, accuracy, and flexibility. However, whilst bridge based measurement configurations remove many of the issues associated with making measurements at accuracies of sub-parts, a part, or few parts per million they still require, in many instances, that a null point be determined where the bridge is balanced. However, this becomes increasingly difficult within electrically noisy environments, with modern digital multimeters, and where the desired measurement point within the electrical system is physically difficult to access particularly when improved accuracy in calibration, standards, and measurements on circuits and components means measurement systems must operate at 50 parts per billion (ppb) and below. In order to address this, a null detector design is provided supporting operation within such electrically noisy environments with physical separation of the null detector measurement circuit from the electrical test equipment.

Claims11

Dependent claims

A device comprising:

an input port comprising an upper signal rail and a lower signal rail;
a first resistor having a first end coupled to the upper signal rail of the input port;
a second resistor having a first end coupled to the upper signal rail of the input port;
a third resistor having a first end coupled to the other end of the first resistor and a second distal end coupled to the lower signal rail of the input port;
a fourth resistor having a first end coupled to the other end of the second resistor and a second distal end coupled to the lower signal rail of the input port;
a first output port coupled to the other end of the first resistor and the first end of the third resistor;
a second output port coupled to the other end of the second resistor and the first end of the fourth resistor;
and
one of:
a null detector coupled to the first output port and the second output port and an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment;
a null detector coupled to the first output port and the second output port, an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment, and a synchronization circuit coupled to the null detector for receiving first electrical signals from the remote test equipment and providing second electrical signals to the null detector;
and
a null detector coupled to the first output port and the second output port, an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment, a first sample and hold circuit coupled to the upper signal rail, a second sample and hold circuit coupled to the lower signal rail, and a synchronization circuit coupled to the null detector for receiving first electrical signals from the remote test equipment and providing second electrical signals to the null detector and third electrical signals to the first sample and hold circuit and second sample and hold circuit;
wherein
in a first configuration the first resistor and fourth resistor are light dependent resistors which are each optically illuminated with first synchronized optical signals having the same time dependent variation in illumination;
in a second configuration the second resistor and third resistor are light dependent resistors which are each optically illuminated with second synchronized optical signals having the same time dependent variation in illumination;
in a third configuration the first resistor and fourth resistor are light dependent resistors which are each optically illuminated with third synchronized optical signals having the same time dependent variation in illumination and the second resistor and third resistor are light dependent resistors which are each optically illuminated with synchronized fourth optical signals having the same time dependent variation in illumination.

14 more elements

A method comprising:

providing a resistive bridge circuit comprising N light dependent resistors (LDRs) and M=N−4 resistors, where both N is an integer and has a value of 1≤N≤4;
driving the N light dependent resistors with R optical signals having a pulse repetition frequency f0 and each pulse having a predetermined intensity profiles;
and one of:
providing a null detector coupled to the first output port and the second output port, and providing an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment;
providing a null detector coupled to the first output port and the second output port, providing an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment, and providing a synchronization circuit coupled to the null detector for receiving first electrical signals from the remote test equipment and providing second electrical signals to the null detector;
and
providing a null detector coupled to the first output port and the second output port, providing an optical emitter coupled to the null detector for optically transmitting an output of the null detector to remote test equipment, providing a first sample and hold circuit coupled to the upper signal rail, providing a second sample and hold circuit coupled to the lower signal rail, and providing a synchronization circuit coupled to the null detector for receiving first electrical signals from the remote test equipment and providing second electrical signals to the null detector and third electrical signals to the first sample and hold circuit and second sample and hold circuit.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/208,016Filed 3 Dec 2018 · us provisional application
Priority: 4 Dec 2017
Published: US 2019/0170796 A16 Jun 2019
Granted: 24 Nov 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G01R 17/14
AC or DC measuring bridges: with indication of measured value by calibrated null indicator, e.g. percent bridge, tolerance bridge
G01R 15/22
Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks: using light-emitting devices, e.g. LED,…
G01R 15/241
Using light-modulating devices: using electro-optical modulators, e.g. electro-absorption
G01R 15/247
Using light-modulating devices: details of the circuitry or construction of devices covered by G01R15/241 - G01R15/246