Cash Till Load Cell Verification for Jitter and Drift
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Solution Overview
Problem
Cash till load cells suffer from random fluctuations ('jitter') and gradual changes ('drift') in signal output, leading to incorrect calculations of cash amounts and inability to differentiate between different denominations of coins or notes, resulting in inaccuracies in monitoring transactions.
Innovation Solution
A method that takes successive readings from the load cell, compares them to determine verified values by accounting for jitter and drift, calculates an average value over time, and uses these values to determine changes in cash amounts while the till drawer is closed, with error handling for incorrect denominations and foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If load cells are used to weigh compartments in a cash till, then the amount of cash can be monitored without removing it from the till, but the load cells suffer from random fluctuations (jitter) and gradual changes (drift) in signal output leading to incorrect calculations
Solution Approach 1:
The system performs preliminary actions by taking multiple successive readings from the load cell before making a determination. By comparing a given reading with subsequently taken readings and storing it as a verified value only if it differs by less than a predetermined amount, the system prepares accurate baseline data before final cash amount calculation, thereby compensating for jitter and drift effects
Solution Approach 2:
The system implements feedback by continuously monitoring load cell readings and comparing each reading with subsequent readings. When a reading differs by more than the predetermined amount (indicating jitter or drift), the system does not store it as a verified value and instead continues taking readings until a verified value is obtained. This feedback mechanism ensures that only accurate readings are used for cash amount determination
2Extent of automation
If load cells provide continuous weight readings, then cash monitoring is automated, but the readings are affected by jitter and drift requiring multiple comparisons and verified value storage
Solution Approach 1:
The system applies partial action by not using every reading from the load cell for cash calculation. Instead, it takes multiple readings and selectively stores only those that meet the verification criterion (differing by less than a predetermined amount from subsequent readings). This partial use of readings filters out inaccurate data caused by jitter and drift while maintaining automated monitoring
3Productivity
If compartments are assigned to specific denominations, then transaction monitoring is simplified, but incorrect denominations or foreign objects placed in compartments cause incorrect determinations of cash amount
Solution Approach 1:
The system applies preliminary anti-action by preparing verified values through multiple reading comparisons before using them to determine cash amounts. This preliminary verification process creates a buffer against errors that may occur later when incorrect denominations or foreign objects are placed in compartments, as the verified values represent the most accurate baseline available
Data Source
AI summary
A cash till having a drawer (2) with a plurality of compartments (4) for storing coins, notes or vouchers. Each compartment (4) has an associated load cell (6), which produces a signal that is proportional to the weight of the compartment contents. The signal is provided to a monitoring apparatus (10) that takes readings from the load cell (6) while the till drawer (2) is closed. If a preceding reading is within a threshold amount of the current reading, then the preceding reading is stored as a verified value. The method removes jitter and drift in the signals produced by the load cells (6) of the cash till.