Capacitance Diaphragm Gauge Thermal Insulation via Vacuum Enclosure
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Solution Overview
Problem
Existing capacitance diaphragm gauge (CDG) sensors face challenges in maintaining accuracy and sensitivity due to heat transfer issues in high-temperature environments, which can cause fluctuations in the measured capacitance.
Innovation Solution
A CDG assembly with a vacuum enclosure that provides thermal insulation and barometric pressure isolation around the CDG sensor, combined with an internal heater and temperature sensor for maintaining a selected operating temperature, and hermetically sealed connectors to prevent heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the CDG sensor is placed in a high-temperature environment for process monitoring, then the sensor can measure pressure in elevated temperature environments, but heat transfer into or out of the sensor causes temperature fluctuations that alter thermal resistances and capacitance measurements, reducing measurement precision
Solution Approach 1:
The system is divided into two separate environments: a high-temperature process environment and a controlled measurement environment. The diaphragm separates these environments, allowing the sensor electronics to remain in a stable temperature zone while the process side experiences elevated temperatures. This segmentation prevents heat transfer from affecting the sensitive measurement components.
Solution Approach 2:
The diaphragm acts as an intermediary element that transmits mechanical stress from the high-temperature process environment to the sensor side without allowing direct thermal coupling. The diaphragm isolates the sensitive capacitance measurement components from thermal fluctuations while still responding to pressure changes in the hot environment.
2Loss of energy
If active cooling or passive insulation techniques are used to protect the electronics, then heat transfer is reduced, but these techniques are limited by a maximum heat differential between the electronics and the sensor
Solution Approach 1:
The system separates the thermal zones by placing the electronics in a distinct thermal environment from the sensor. The enclosure creates a thermal boundary that allows the electronics to operate at a different temperature than the sensor, enabling operation beyond previous heat differential limits.
Solution Approach 2:
The vacuum enclosure creates a thermally inert environment around the sensor, reducing heat transfer pathways. The vacuum acts as a thermal barrier that minimizes conductive and convective heat transfer, allowing the system to handle larger temperature differences between the sensor and electronics.
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
The solution effectively prevents significant heat transfer into or out of the CDG sensor, maintaining its accuracy and sensitivity even in high-temperature environments, while allowing for precise control of the operating temperature.
Implementation Method 1
The vacuum enclosure provides thermal insulation and barometric pressure isolation around the CDG sensor
Implementation Method 2
The internal heater is responsive to external heater control signals
Implementation Method 3
The temperature sensor generates a temperature signal
Data Source
AI summary
A capacitance diaphragm gauge (CDG) assembly includes a CDG sensor positioned within a vacuum enclosure, which is maintained at a vacuum. The CDG sensor generates sensor signals responsive to a pressure of an applied gas. The vacuum enclosure provides thermal insulation around the CDG sensor. The CDG sensor is maintained at a selected operating temperature using an internal heater positioned on the CDG sensor. The internal heater is responsive to external heater control signals. The temperature of the CDG sensor is monitored using an internal temperature sensor mounted on the CDG sensor. The temperature sensor generates a temperature signal. The vacuum enclosure includes an end cap that seals the vacuum enclosure. Connectors positioned through the end cap communicate the sensor signals, the heater control signals and the temperature signals through the end cap. The connectors are hermetically sealed to the end cap to maintain the vacuum within the vacuum enclosure.