Wireless Process Instrument Arbitration Logic for Power and EMI
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Solution Overview
Problem
Wireless process measurement instruments face challenges with steeply varying power consumption and mutual electromagnetic interference between measurement and communication units, which affect battery life and instrument performance.
Innovation Solution
The measurement and communication units share a common memory for sequential read/write access, with arbitration logic ensuring they do not operate simultaneously, reducing power consumption spikes and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the measurement unit and communication unit operate independently with separate duty cycles, then each unit can optimize its own power consumption, but the aggregated power consumption exhibits steep variations with periods of extremely high and low consumption
Solution Approach 1:
The patent merges the operation schedules of the measurement unit and communication unit by implementing a coordinated duty cycle where both units are synchronized to be active during overlapping time periods. This coordination smooths the aggregated power consumption by ensuring that when one unit becomes inactive, the other remains active, thereby avoiding extreme power drops and stabilizing the overall power draw from the battery.
2Area of stationary object
If the measurement unit and communication unit are integrated in proximity to minimize form factor, then the device size is reduced, but mutual electromagnetic interference occurs between the RF/microwave measurement module and the wireless communication module
Solution Approach 1:
The patent implements preliminary action by introducing RF filtering and shielding measures during the design and integration phase, before the electromagnetic interference problems manifest during operation. RF filters are placed in the signal paths of both measurement and communication modules to preemptively attenuate interfering frequencies, and the modules are positioned and oriented during PCB layout to minimize coupling, thereby preventing EMI issues before they occur.
3Object-generated harmful factors
If discrete RF filters are used to block interference between modules, then electromagnetic interference is reduced, but receiver performance degrades due to insertion loss and noise factor
Solution Approach 1:
The patent applies local quality by implementing differential filtering strategies where the RF filters are designed with different characteristics for the measurement path and communication path based on their specific frequency requirements and interference profiles. The filters are positioned locally at each module's RF interface rather than using a single centralized filter, allowing optimization of filter specifications for each application to minimize impact on receiver performance while maintaining interference rejection.
4Object-generated harmful factors
If a common time division scheme is implemented to avoid simultaneous transmission, then electromagnetic interference is eliminated, but synchronous control of both modules by a common control application is required
Solution Approach 1:
The patent implements periodic action by using fixed, predetermined duty cycles for both the measurement unit and communication unit that are designed to overlap in a regular periodic pattern. Instead of dynamic synchronous control, the units operate on predetermined schedules where measurement occurs during specific time windows and communication occurs during overlapping or adjacent windows, eliminating the need for complex real-time coordination while still preventing simultaneous high-power transmission.
Data Source
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AI summary
A process measurement instrument adapted for wireless communication, comprising a measurement unit (7) arranged to determine a measurement value of a process variable, a memory (21) arranged to store a current measurement value of the process variable,a wireless communication unit (8), arranged to access the current measurement value and communicate the current measurement value over a wireless communication channel according to a protocol with intermittently active communication, and arbitration logic (22), in communication with the measurement unit and the wireless communication unit, and arranged to ensure that active periods of the measurement unit occur when the wireless communication is inactive. The measurement unit and communication unit are thus able to share information via the common memory, e.g. By sequential read/write access. This avoids the need for simultaneous activity.The invention can be especially advantageous when the instrument is powered by an internal power store, such as a battery, and extend the lifetime of such a power store.