# US 2020/0400751 A1 · Estimation of unknown electronic load > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0400751 A1 - Document ID: US20200400751A1 - Status: Published application - Kind: A1 - Application number: 16/894,633 - Filed: 2020-06-05 - Published: 2020-12-24 - Earliest claimed: 2019-06-19 - Assignees: Keithley Instruments, LLC - Applicants: Keithley Instruments, LLC - Inventors: William C. Weeman - Web page: https://patentgrep.com/patent/US20200400751A1 ## CPC - G01R 31/2839: {using signal generators, power supplies or circuit analysers (G01R31/2879 takes precedence; multimeters G01R15/12, network analysers G01R27/28)} - G01R 31/3842: combining voltage and current measurements - G01R 27/02: Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) - G01R 31/2812: {Checking for open circuits or shorts, e.g. solder bridges; Testing conductivity, resistivity or impedance (of connections G01R31/66)} - G01R 31/2879: {related to electrical aspects, e.g. to voltage or current supply or stimuli or to electrical loads} - G01R 31/3004: {Current or voltage test} - G01R 31/31924: {Voltage or current aspects, e.g. driver, receiver} - G01R 35/005: {Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A test and measurement instrument including a voltage source configured to output a source voltage, a current sensor, and one or more processors. The one or more processors are configured to determine an estimation of a load of an unknown connected device under test based on the source voltage, the current sensor, and a voltage of the connected device under test without any prior knowledge of the connected device under test. ## Claims ### Claim 1 A test and measurement instrument, comprising: a voltage source configured to output a source voltage; a current sensor configured to sense a current through a connected device under test; and one or more processors configured to determine an estimation of a load of an unknown connected device under test based on the source voltage, the current, and a voltage of the unknown connected device under test. ### Claim 2 (depends on 1) The test and measurement instrument of claim 1, wherein the one or more processors are further configured to determine the estimation of the load iteratively. ### Claim 3 (depends on 2) The test and measurement instrument of claim 2, wherein the estimation of the load includes an estimation of a resistance and a capacitance or an estimation of a resistance and an inductance. ### Claim 4 (depends on 3) The test and measurement instrument of claim 3, wherein the one or more processors are further configured to iteratively adjust a value of the resistance based on whether an output of a normal resistance equation is positive or negative and adjust a value of the capacitance or the inductance based on whether an output of a normal capacitance or inductance equation is positive or negative. ### Claim 5 (depends on 4) The test and measurement instrument of claim 4, wherein when the output of the normal resistance equation is positive, the value of the resistance is adjusted upwards, and wherein when the output of the normal capacitance or inductance equation is positive, the value of the capacitance or inductance is adjusted upwards. ### Claim 6 (depends on 5) The test and measurement instrument of claim 5, wherein an amount of the adjustment of the value of the resistance is based on a current estimated value of the resistance, and wherein the amount of the adjustment of the value of the capacitance or inductance is based on a current estimated value of the capacitance or inductance. ### Claim 7 (depends on 5) The test and measurement instrument of claim 5, wherein an amount of the adjustment of the value of the resistance is a predetermined incremental value, and wherein the amount of the adjustment of the value of the capacitance or inductance is a predetermined incremental value. ### Claim 8 (depends on 2) The test and measurement instrument of claim 2, wherein the one or more processors are further configured to determine the estimation of the load iteratively by: selecting arbitrary starting values for the load; determining simultaneously the source voltage and the voltage of the connected device under test; determining based on the source voltage, the voltage of the connected device under test, and the arbitrary starting values for the load whether to adjust an estimated value of a resistance of the load in a positive or negative direction and whether to adjust an estimated value of a capacitance or inductance of the load in a positive or negative direction; and adjusting the arbitrary starting values for the resistance and the capacitance or inductance either positively or negatively such that the adjusted values represent the estimation of the load. ### Claim 9 (depends on 8) The test and measurement instrument of claim 8, wherein the one or more processors are further configured to determine the estimation of the load iteratively by: determining simultaneously another output voltage from the voltage source and the voltage of the attached device under test; determining based on the output voltage, the voltage of the attached device under test, and the adjusted values for the load whether to adjust the estimated value of the resistance in a positive or negative direction and whether to adjust the value of the estimated capacitance or inductance in a positive or negative direction; and adjusting the estimated values for the resistance and the capacitance or inductance either positively or negatively such that the adjusted estimated values represent a refined estimation of the load. ### Claim 10 (depends on 8) The test and measurement instrument of claim 8, wherein the one or more processors are further configured to limit the adjusted value of the resistance based on an upper bound and a lower bound and to limit the adjusted value of the capacitance or inductance based on an upper bound and a lower bound. ### Claim 11 (depends on 10) The test and measurement instrument of claim 10, wherein the upper and the lower bounds of the values of the resistance and the capacitance or inductance are set by a user. ### Claim 12 (depends on 7) The test and measurement instrument of claim 7, wherein the arbitrary starting value is selected to approximate a condition where the device under test is not attached. ### Claim 13 A method for estimating an unknown load coupled to a test and measurement instrument, comprising: acquiring a voltage at a circuit node between a current sensor and a device under test, wherein the device under test presents the unknown load to the test and measurement instrument; determining an output voltage forced on the current sensor; determining a current through the device under test using the current sensor; and determining an estimated value of the load based on the voltage at the circuit node, the current, and the output voltage. ### Claim 14 (depends on 13) The method of claim 13, further comprising iteratively determining a new estimated value of the load, the load including either a resistance and a capacitance or a resistance and an inductance. ### Claim 15 (depends on 14) The method of claim 14, wherein determining the new estimated value of the resistance and the capacitance or inductance of the attached device under test includes: selecting arbitrary starting values for the resistance and the capacitance or inductance; determining simultaneously the output voltage and the voltage at the circuit node; determining based on the output voltage, the voltage at the circuit node, and the arbitrary starting values for the resistance and capacitance or inductance whether to adjust the value of the resistance in a positive or negative direction and whether to adjust the value of the capacitance or inductance in a positive or negative direction; and creating the new estimated value for the resistance and the capacitance or inductance by adjusting the arbitrary starting value either positively or negatively. ### Claim 16 (depends on 15) The method of claim 15, wherein determining the estimation of the resistance and the capacitance of the attached device under test further includes: determining simultaneously another output voltage and the voltage at the circuit node; determining based on the output voltage, the voltage at the circuit node, and the new estimated values for the resistance and the capacitance or the inductance whether to adjust the value of the resistance in a positive or negative direction and whether to adjust the value of the capacitance or inductance in a positive or negative direction; and adjusting the new estimated value for the resistance and the capacitance or inductance either positively or negatively. ### Claim 17 (depends on 14) The method of claim 14, wherein the new estimated value of the resistance is limited based on an upper bound and a lower bound and the new estimated value of the capacitance or inductance is limited based on an upper bound and a lower bound. ### Claim 18 (depends on 17) The method of claim 17, wherein the upper and the lower bounds of the values of the resistance and the capacitance or inductance are set by a user. ### Claim 19 (depends on 14) The method of claim 14, wherein the arbitrary starting value is selected to approximate a condition when the device under test is not attached. ### Claim 20 (depends on 14) The method of claim 14, wherein determining an estimation of a resistance and a capacitance or inductance includes adjusting a value of the estimated resistance based on whether an output of a normal resistance equation is positive or negative and adjusting a value of the estimated capacitance or inductance based on whether an output of a normal capacitance or inductance equation is positive or negative.