Capacitance Powder Flow Meter Thermal Drift Compensation
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Solution Overview
Problem
Conventional capacitance-type apparatuses for measuring powder flow rates require excessive carrier gas to correct for temperature changes, leading to increased energy consumption and inaccurate measurements, especially when dealing with low flow rates or high-temperature powders.
Innovation Solution
A capacitance-based apparatus with a measuring pipe, a measuring electrode, and temperature sensors for atmospheric and carrier gas temperature compensation, allowing for accurate flow rate measurement using a single measuring electrode without the need for duplicate carrier gas streams, and featuring a protecting pipe for precise temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitance-type apparatus uses two parallel electrodes (measuring electrode and adjusting electrode) to correct measurement errors caused by temperature changes, then measurement accuracy is improved, but the amount of carrier gas required doubles and energy consumption increases
Solution Approach 1:
The patent extracts the temperature correction function from the second electrode and relocates it to a separate temperature sensor. This allows the adjusting electrode to be eliminated, reducing carrier gas consumption while maintaining measurement accuracy through thermal compensation using the extracted temperature data.
Solution Approach 2:
The patent makes the temperature sensor serve dual purposes: it monitors temperature for thermal compensation of the measuring electrode and simultaneously provides the correction data needed previously requiring a separate adjusting electrode. This multi-functional approach eliminates redundant components and reduces energy consumption.
2Reliability
If a conventional capacitance-type apparatus uses two parallel electrodes to compensate for environmental temperature changes, then measurement reliability is improved, but the device complexity increases due to requiring duplicate sensor systems
Solution Approach 1:
The patent extracts the temperature measurement function from the adjusting electrode and places it in a dedicated temperature sensor. This simplifies the overall sensor configuration by eliminating redundant components while maintaining the reliability needed for accurate flow rate measurement through thermal compensation.
Solution Approach 2:
The patent introduces a temperature sensor as an intermediary element that mediates between the environmental conditions and the measuring electrode. This intermediary provides temperature data for compensation calculations, simplifying the system architecture compared to using a parallel adjusting electrode while maintaining measurement stability.
3Adaptability or versatility
If compressed air is used as carrier gas for transporting powder through a conveying pipe, then powder handling capability is improved, but measurement accuracy deteriorates when the same compressed air is not available for the adjusting electrode
Solution Approach 1:
The patent extracts the temperature compensation function from the adjusting electrode and implements it through a temperature sensor that directly measures the temperature of the compressed air carrier gas. This allows accurate thermal compensation using the actual carrier gas temperature without requiring duplicate air supplies, maintaining both powder handling capability and measurement precision.
4Speed
If the measuring electrode is exposed directly to the carrier gas stream for flow rate measurement, then measurement responsiveness is improved, but measurement accuracy deteriorates due to direct thermal influence from temperature fluctuations
Solution Approach 1:
The patent introduces a temperature sensor as an intermediary that measures the temperature of the carrier gas without being directly exposed to the powder-laden stream. This intermediary provides thermal compensation data that corrects the measuring electrode readings, maintaining responsiveness while improving accuracy by accounting for temperature fluctuations.
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 high-accuracy measurement of powder flow rates with reduced energy consumption and minimal environmental influence, maintaining accuracy even at low flow rates and varying temperatures.
Implementation Method 1
an electrode (a measuring electrode) for measuring changes of capacitance in the measuring pipe
Implementation Method 2
a sensor (an atmospheric temperature sensor) for measuring the temperature of the atmosphere and a sensor (a carrier-gas-temperature sensor) for measuring the temperature of the carrier gas
Implementation Method 3
a circuit (a transducer) for transducing the capacitance as an output of the measuring electrode to a flow rate indicated by a display
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3~4
AI summary
[Problems] For an apparatus for measuring a flow rate of a powder when a powder is conveyed by using air as a carrier gas, which apparatus measures the flow rate based on the change of capacitance of the powder to be measured, to provide the apparatus that can measure the flow rate of a powder with high accuracy by compensating for the effect of the thermal drift of the capacitance. [Means for Solving Problems] The apparatus for measuring a flow rate of a powder, which apparatus uses capacitance, comprises: a protecting pipe for conveying a powder, a housing pipe having measuring electrodes, and a transducer for outputting an output of the measuring electrode to a display. It further comprises an atmospheric temperature sensor and a carrier-gas-temperature sensor 31. The sensor 31 is directly fixed to the protecting pipe 20 at a place that does not overlap the housing pipe 10, and comprises a circuit for compensating for the output of the measuring electrode, which output is the capacitance determined based on a graph of a curve of the relationship between a capacitance and a flow rate, based on the difference between the output of the atmospheric temperature sensor and the output of the carrier-gas-temperature sensor.