Notification Appliance Circuit Adaptation to End-of-Line Resistor Values
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Solution Overview
Problem
Existing alarm system technologies face challenges in accurately detecting and adapting to varying End-of-Line (EOL) resistor values and localizing ground faults, leading to inefficient retrofit installations and incorrect supervision current measurements, which can result in faulty circuit reporting and increased troubleshooting time and costs.
Innovation Solution
The method involves automatically detecting and adapting to a wide range of EOL resistor values by measuring voltages on both NAC terminals, calculating the total external wiring resistance, and using a processor to determine if the EOL resistor value is within a predetermined range, while also localizing ground faults by periodically changing the ground offset voltage and monitoring voltage changes on I/O terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a predetermined EOL resistor value is used in known NAC supervision schemes, then the supervision current can be measured within a normal range, but the system cannot adapt to different control panel models requiring different EOL resistor values
Solution Approach 1:
The system dynamically adjusts the expected supervision current range based on the detected EOL resistor value. Instead of using a fixed predetermined value, the control panel measures the actual EOL resistor value and automatically configures the supervision parameters to match, enabling adaptation to different control panel models while maintaining measurement accuracy.
Solution Approach 2:
The system changes the operational parameters (supervision current thresholds) based on the detected EOL resistor value. By measuring the actual EOL resistor value first, the system adjusts the supervision current measurement parameters accordingly, allowing accurate supervision across different EOL resistor values and control panel models.
2Reliability
If tuning the NAC circuit is performed to match existing EOL resistor values during retrofit, then correct supervision can be achieved, but the installation process becomes time consuming and inconvenient
Solution Approach 1:
The system performs self-configuration by automatically detecting the EOL resistor value during installation and configuring the supervision parameters accordingly. This eliminates the need for manual tuning or reference resistor installation, allowing the system to adapt automatically to different control panel models and reducing installation time while ensuring correct supervision.
Solution Approach 2:
The system performs preliminary detection of the EOL resistor value before configuring supervision parameters. By measuring the actual EOL resistor value first and then automatically setting the appropriate supervision thresholds, the system prepares the correct configuration in advance, eliminating the need for time-consuming manual tuning during installation.
3Reliability
If ground fault troubleshooting is performed using known methods, then ground faults can be detected, but the process requires expensive galvanic isolation of each NAC and extensive troubleshooting time
Solution Approach 1:
The system uses the EOL resistor as an intermediary element for ground fault detection. By measuring changes in the EOL resistor value or supervision current characteristics, the system can detect ground faults without requiring galvanic isolation or complex additional hardware, simplifying the overall system while maintaining reliable fault detection capability.
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
This approach simplifies retrofit installations by eliminating the need to locate and replace EOL resistors, ensures correct NAC operation with new hardware, and reduces troubleshooting time and costs by accurately detecting and reporting ground faults and EOL resistor values.
Implementation Method 1
measuring a voltage on a first terminal and measuring a voltage on a second terminal of the notification appliance circuit
Implementation Method 2
periodically changing the ground offset voltage and monitoring voltage changes on I/O terminals
Data Source
Figure 1
Figure 2
AI summary
An apparatus and method for detection and adaption to an end-of-line resistor in a NAC of a control panel or power booster of, for example, an alarm system and for ground fault localization in the alarm system are provided. The apparatus can include a notification appliance circuit, where the notification appliance circuit includes first and second analog input terminals, where the notification appliance circuit includes first and second external output terminals, and where the notification appliance circuit includes an end-of-line resistor. Current can be driven through the notification appliance circuit via the first and second analog input terminals, and voltage can be measured at each of the first and second external output terminals. The measured voltage can be indicative of one of a value of the end-of-line resistor or that a state of the notification appliance circuit is one of open, shorted, ground faulted, or normal.