Load Cell with Differential Sensor Compensation
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Solution Overview
Problem
Conventional load cells experience temporary shifts in measuring characteristics due to rapid temperature changes and temperature gradients, which affect their precision and accuracy.
Innovation Solution
A load cell design featuring a sensor carrier plate movably coupled between its inner and outer portions, with at least one sensor generating a signal of opposite sign to compensate for temperature changes, and additional sensors positioned to average temperature effects, ensuring high precision and sensitivity to applied loads even in environments with fast temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sensor is used in the outer portion of the sensor carrier plate, then the load cell can measure displacement, but the measuring characteristic shifts temporarily under fast temperature changes or temperature gradients
Solution Approach 1:
The sensor carrier plate is divided into inner and outer portions with sensors strategically positioned in both regions. This segmentation allows the system to capture differential displacement signals that are insensitive to uniform temperature expansions, thereby maintaining measurement precision while achieving temperature compensation.
Solution Approach 2:
The sensor carrier plate acts as an intermediary element that movably couples the inner and outer portions. This intermediary structure enables the sensors to measure relative displacement between the two portions, which automatically compensates for temperature-induced shifts in the measuring characteristic.
2Device complexity
If sensors are arranged only in the outer portion of the sensor carrier plate, then the structure is simple, but temperature effects cannot be averaged out
Solution Approach 1:
The sensor arrangement is segmented into inner and outer portions on the sensor carrier plate. This segmentation enables the system to average temperature effects by comparing signals from both regions, improving temperature compensation capability while maintaining reasonable structural complexity.
3Device complexity
If the sensor carrier plate is rigidly coupled to the membrane, then the structure is simple, but automatic compensation for fast temperature changes is not achieved
Solution Approach 1:
The sensor carrier plate is movably coupled to both the membrane and the second membrane, creating a dynamic structure that can automatically adjust to temperature changes. This movable coupling enables automatic temperature compensation by allowing the sensor carrier plate to shift position in response to thermal expansions, thereby maintaining measurement accuracy without complex active control systems.
4Reliability
If a second membrane is added to support the sensor carrier plate, then automatic temperature compensation is achieved, but the device complexity increases
Solution Approach 1:
The second membrane is implemented as a flexible thin film structure that supports the sensor carrier plate. This flexible shell approach achieves automatic temperature compensation through its ability to deform and accommodate thermal expansions, while maintaining relatively simple device complexity compared to rigid support structures.
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 differential sensor arrangement provides high precision and automatic compensation for temperature changes and gradients, reducing sensitivity to off-center forces and allowing for accurate measurement of loads with improved linearity and zero-point stability.
Implementation Method 1
the sensor and the further sensor are adapted to sense the distance to the load receiving membrane
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A load cell comprises a cylindrical ring (3) which at one end is closed by a membrane (1) for receiving a load or force to be measured, and further comprises a sensor carrier plate (7) arranged in a cavity (6) formed by said ring (3) and membrane (1). The sensor carrier plate (7) is coupled to said membrane (1) to undergo a displacement upon deflection of the membrane (1). The sensor carrier plate (7) has an inner and an outer portion and carries in the outer portion at least one sensor (9) adapted for sensing said displacement and generating a signal due to the load or force applied to the membrane (1). To provide a load cell which automatically compensates fast changing temperatures and temperature gradients, the sensor carrier plate (7) is movably coupled to the membrane (1) at locations between the inner portion and the outer portion, and at least one further sensor (10) is arranged in the inner portion, said sensor (10) generating a signal changing with opposite sign with respect to the signal of the sensor (9).