Coriolis Flowmeter Pickoff Ratio Detection for Magnetic Tampering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Coriolis flowmeters are vulnerable to external magnetic fields that can manipulate flow readings, posing a risk in transactions and requiring a method to detect such interference.
Innovation Solution
A Coriolis flowmeter system that includes a meter electronics configured to monitor pick-off sensor voltages and determine a pick-off ratio (PORATIO), comparing it against a predetermined limit (POLIMIT) to detect the presence of external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external magnets are placed near pickoff sensors, then flow readings can be manipulated to indicate more or less flow, but this creates vulnerability to tampering and measurement accuracy degradation
Solution Approach 1:
The system performs preliminary characterization of the magnetic field environment during installation and operation. By continuously monitoring pickoff sensor voltages and calculating PORATIO, the system establishes a baseline and detects deviations caused by external magnets before they can significantly manipulate flow readings, enabling early warning and prevention of tampering
Solution Approach 2:
The system implements continuous feedback monitoring by comparing real-time pickoff sensor voltage ratios against expected ranges. When external magnets disturb the magnetic field and cause PORATIO to fall outside predetermined limits, the system generates alerts and can trigger corrective actions, creating a closed-loop protection mechanism that counteracts manipulation attempts
2Reliability
If magnetic field detection and monitoring systems are added to Coriolis flowmeters, then vulnerability to external magnetic field manipulation is reduced, but device complexity increases
Solution Approach 1:
The meter electronics performs multiple functions using the same hardware components: it drives the pickoff sensors for normal flow measurement, processes the sensor signals to calculate PORATIO for magnetic field detection, and monitors process variables for tamper detection. This multi-functionality allows magnetic field detection without adding separate dedicated hardware systems, thereby limiting complexity increase
Solution Approach 2:
The system detects magnetic field interference by monitoring changes in electrical parameters (pickoff sensor voltages and their ratios) rather than adding physical magnetic field sensors. By analyzing voltage ratio deviations and process variable changes, the system achieves tamper detection through parameter analysis of existing signals, avoiding additional complex detection hardware
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
Effectively identifies potential tampering by external magnetic fields, reducing false alarms through additional process variable checks, ensuring accurate flow measurements.
Implementation Method 1
As flowtubes vibrate, pickoff bobbin wires pass through a magnetic field of a magnet, which generates a voltage
Implementation Method 2
If the magnetic field is disturbed or changes during the meter's operation, the meter's output will be affected
Data Source
AI summary
A Coriolis flowmeter (5) is provided, the Coriolis flowmeter (5) comprising flow conduits (103A, 103B), having a driver (104), and pick-off sensors (105, 105′) connected thereto. A meter electronics (20) is configured to drive the driver (104) to oscillate the flow conduits (103A, 103B), and to receive signals from the pick-off sensors (105, 105′). The meter electronics (20) is configured to capture voltages for both the pick-off sensors (105, 105′) and determine a PORATIO and determine whether the PORATIO falls within a predetermined POLIMIT. The presence of an external magnetic field is indicated if the PORATIO falls outside the predetermined POLIMIT.