DIGITAL VOLTMETER TOPOLOGY

• US 20140285181A1
• Filed: 03/22/2013
• Published: 09/25/2014
• Est. Priority Date: 03/22/2013
• Status: Active Grant

• Current Assignee: Tektronix Incorporated (Fortive Corp.), Keithley Instruments, Inc.
• Original Assignee: Keithley Instruments, Inc.
• Inventors: Goeke, Wayne
• Granted Patent: US 9,541,584 B2
• Time in Patent Office: Days
• US Class Current: 324/123.R
• CPC Class Codes: G01R 15/22 using light-emitting devices, e.g. LED, optocouplers G01R31/31901 takes precedence
• CPC Class Codes: G01R 19/2503 for measuring voltage only, e.g. digital volt meters (DVM's) G01R19/2506 - G01R19/257 take precedence

Abstract

A system may include two input terminals, e.g., HI and LO, and a floating circuit that is physically separate from the input terminals and includes a gain amplifier. The floating circuit can be surrounded by a conductive enclosure that is electrically connected to the second input terminal. The floating circuit can further switch between input signals received from the first and second input terminals to the gain amplifier and the floating circuit ground.

Claims

1. A system comprising:

a first input terminal;

a second input terminal; and

a floating circuit that is physically separate from the first and second input terminals, includes a gain amplifier, and is surrounded by a conductive enclosure that is electrically connected to the second input terminal, wherein the floating circuit is configured to switch between input signals received from the first and second input terminals to the gain amplifier and the floating circuit ground.

2. The system of claim 1, wherein the first input terminal is configured to receive a HI input signal, and further wherein the second input terminal is configured to receive a LO input signal.

3. The system of claim 1, wherein the conductive enclosure is made of metal.

4. The system of claim 1, further comprising a buffer amplifier with its input connected to the first input terminal and its supply referenced to the second input terminal configured to allow either floating circuit input to be pre-charged to a voltage nearly equal to the first terminal voltage prior to the first terminal be connected to that floating circuit input.

5. The system of claim 1, further comprising an analog-to-digital converter (ADC) configured to provide an output to first isolated communication means.

6. The system of claim 5, wherein the first isolated communication means includes an opto-coupling component.

7. The system of claim 5, wherein the first isolated communication means is coupled with a second isolated communication means.

8. The system of claim 7, wherein the first and second isolated communication means each include an opto-coupling component.

9. The system of claim 7, wherein the second isolated communication means is positioned outside a guard shield configured to physically surround the floating circuit.

10. The system of claim 1, further comprising a first isolated power supply configured to provide power to the second terminal-based circuitry from an earth GND power source, and a second isolated power supply configured to provide power to the floating circuitry from the output of the first isolated power supply.