Temperature Compensated Current Source for Cryogenic Testing
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Solution Overview
Problem
Current temperature compensation techniques for cryogenic electronic testing are inadequate as they instantaneously compensate for temperature effects, failing to account for the time it takes for semiconductor current sources to absorb thermal energy, leading to inaccurate test currents due to current drift.
Innovation Solution
A system with a controller that receives temperature signals, identifies thermal saturation time, and generates a time constant adjustment signal to delay temperature compensation, adjusting the RC network's time constant to match the thermal saturation time, thereby compensating for temperature effects on current sources at a later stage when current drift occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If instantaneous temperature compensation is applied to the current source circuit, then the response speed of temperature compensation is improved, but the accuracy of current compensation deteriorates due to current drift caused by thermal saturation delay
Solution Approach 1:
The system performs preliminary action by measuring the ambient temperature and calculating the thermal saturation time in advance, before the current drift actually occurs. The controller uses the measured temperature to look up the corresponding thermal saturation time from a pre-stored table, and then adjusts the RC network's time constant proactively to match this predicted delay period. This allows the compensation signal to be ready and properly timed when the thermal saturation effect actually manifests, resolving the contradiction between fast response and accurate compensation.
2Productivity
If the temperature compensation circuit compensates immediately for temperature effects, then the responsiveness to temperature changes is improved, but the current drift cannot be effectively compensated due to mismatch with thermal saturation time
Solution Approach 1:
The system applies dynamics by making the time constant of the RC network adjustable rather than fixed. The controller dynamically changes the time constant based on the measured ambient temperature by selecting different resistance values from a lookup table. This dynamic adjustment ensures that the compensation circuit's time constant always matches the actual thermal saturation time of the current source at the current operating temperature, maintaining both high responsiveness and effective drift compensation across varying temperature conditions.
3Device complexity
If a fixed time constant is used in the RC network, then the circuit complexity is reduced, but the compensation accuracy deteriorates under varying temperature conditions
Solution Approach 1:
The system implements parameter changes by varying the resistance value in the RC network based on temperature. Instead of using a single fixed resistor, the design employs a lookup table that maps ambient temperature values to optimal resistance values. The controller reads the ambient temperature, retrieves the corresponding resistance value from the table, and adjusts the RC network accordingly. This approach maintains relatively simple circuitry while achieving high compensation accuracy across different temperature conditions by adapting the time constant parameter to match actual thermal behavior.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach minimizes current drift by providing precise test currents closer to the target, reducing noise and improving accuracy in cryogenic device testing by dynamically adjusting to temperature changes over the current source's operating life.
Implementation Method 1
identify a thermal saturation time for the current source circuit in response to the temperature being greater than or equal to the temperature threshold
Implementation Method 2
failing to account for the time it takes for semiconductor current sources to absorb thermal energy
Data Source
AI summary
This disclosure relates to systems and methods for current source temperature compensation for use during cryogenic electronic testing. A temperature compensation circuit can provide a temperature compensation signal to a current source circuit configured to provide an electrical current for testing a cryogenic device under test to compensate for temperature effects on the current source circuit based on a time constant adjustment signal. The time constant adjustment signal can adjust a time constant of the temperature compensation circuit to delay by a given amount of time that the temperature compensation circuit compensates for the temperature effects on the current source circuit. A controller can be configured to execute a temperature compensation method to provide the time constant adjustment signal based on at least one temperature signal characterizing a temperature of an environment that includes the current source circuit or a temperature of the current source circuit.