Cryogenic Flowmeter Using Heated Hall Sensors for Magnetic Noise Resistance
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Solution Overview
Problem
Existing flowmeters struggle with accurate flow measurement of extremely-low temperature fluids due to sensitivity issues with Hall elements, susceptibility to external magnetic field noise, and inadequate temperature control, especially in semiconductor manufacturing environments.
Innovation Solution
A flowmeter design incorporating a metal-based wiring substrate with a magnetic sensor package, heater, and temperature control circuit, which maintains a uniform temperature across the substrate and absorbs heat efficiently, using a metal seal and wave washer for sealing, and a double-ferrule Swagelok pipe joint for hermeticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pickup coil with copper winding is used as a magnetic sensor, then it can detect extremely-low temperature fluids, but it becomes susceptible to noise from external magnetic fields
Solution Approach 1:
The patent replaces the copper winding pickup coil (electromagnetic induction system) with a Hall element-based magnetic sensor. This substitution eliminates the antenna effect that causes susceptibility to external magnetic field noise while maintaining the ability to detect magnetic fields from the impeller for flow measurement at extremely-low temperatures.
Solution Approach 2:
The patent changes the operating temperature parameter of the Hall element by introducing a heater and temperature control circuit. By actively controlling the Hall element temperature to remain above −40°C even when measuring extremely-low temperature fluids, the detection sensitivity is maintained while avoiding the low-temperature performance degradation inherent to semiconductor sensors.
2Object-affected harmful factors
If Hall ICs are used as magnetic sensors, then detection is not easily affected by external magnetic field noise, but detection sensitivity decreases at low temperatures
Solution Approach 1:
The patent actively controls the temperature parameter of the Hall element using a heater and temperature control circuit. This ensures the Hall element operates within its optimal temperature range (above −40°C) even when measuring extremely-low temperature fluids, thereby maintaining high detection sensitivity while preserving immunity to external magnetic field noise.
Solution Approach 2:
The patent introduces a heater and temperature control circuit as intermediary components between the Hall element and the extremely-low temperature environment. This intermediary system acts as a thermal buffer, isolating the Hall element from the cold fluid temperature while allowing the flowmeter to measure extremely-low temperature fluids accurately.
3Reliability
If thermal insulation materials are used to prevent condensation and freezing, then the ambient temperature and sensor temperature deviate, making temperature control difficult
Solution Approach 1:
The patent implements a feedback control system where a temperature sensor continuously monitors the Hall element temperature and feeds this information to the temperature control circuit. The control circuit adjusts the heater power accordingly to maintain the Hall element temperature within the specified range, achieving accurate temperature control despite the presence of thermal insulation.
Solution Approach 2:
The patent replaces passive thermal insulation alone with an active temperature control system that uses electrical heating and feedback control. This substitution enables precise temperature management of the Hall element, overcoming the temperature deviation problem caused by thermal insulation while still preventing condensation and freezing.
4Object-affected harmful factors
If the flowmeter is positioned far from motors and power lines to avoid magnetic noise, then the setting area increases and device layout becomes difficult
Solution Approach 1:
The patent replaces the copper winding pickup coil with a Hall element-based magnetic sensor. This substitution fundamentally changes the sensor's electromagnetic characteristics, eliminating the antenna effect that causes susceptibility to external magnetic field noise. As a result, the flowmeter can be positioned close to motors and power lines without suffering from magnetic interference, thereby reducing the required setting area and improving device layout flexibility.
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
Enables accurate flow measurement of fluids across a wide temperature range from −120°C to +150°C, resistant to external magnetic noise, and maintains operation during momentary or abnormal stops, with improved sealing and heat management.
Implementation Method 1
a magnetic sensor package that detects the magnetic force of the impeller
Implementation Method 2
a heater that heats the wiring substrate
Implementation Method 3
by using a semiconductor sensor with a magnetic sensor package... equipped with the magnetic sensor package, the heater, and temperature control circuit on the metal based wiring substrate for temperature control, it is able to perform temperature control of the sensor accurately. Therefore, a uniform temperature across the substrate is maintained
Data Source
AI summary
A flowmeter suitable for flow measurement of extremely-low temperature fluids and high temperature fluids includes a flow path pipe having a flow path for fluid to flow through; an impeller supported in the interior of the flow path pipe in a rotatable manner; and a sensor that measures the flow of the fluid flowing in the flow path through the rotation of the impeller. The sensor has a metal-based wiring substrate inside a sensor housing provided outside the flow path pipe. The wiring substrate is equipped with a magnetic sensor package that detects the magnetic force of the impeller; a heater that heats the wiring substrate; and a temperature control circuit that controls the heater to power on/off based on the temperature of the wiring substrate.