3 The Application

Ammonia is a hazardous material used in several applications, including HVAC systems. Ammonia accidents can lead to emissions, potentially injuring many people nearby. When used in large quantities, monitoring the amount of ammonia in the atmosphere and whether it exceeds a critical level is an important safety measure.

DANGER: This application only monitors current ammonia gas levels, which would be part of the Immediately Dangerous to Life or Health (IDLH) detection system in a fully certified ammonia gas detector.

This application implements a simple ammonia gas detector that monitors ambient ammonia levels. It uses the AVR EA Curiosity Nano Evaluation Kit (EV66E56A) with an Ammonia Click, a Buzz 2 Click, and a 2x2 Click. When the ammonia concentration changes, the analog output of the Ammonia Click changes, which is monitored with an Analog Comparator CIP and compared against a threshold. If the signal exceeds the threshold, the AVR EA generates a PWM signal to drive the Buzz Click while the 2x2 Click adds extra user input buttons. The application is described in detail in Chapter 4.

This application uses the following software tests from the Class B Diagnostic library provided by Microchip: CPU Register Test, SRAM test, Watchdog Timer (WDT) and Flash and EEPROM tests.

However, this is not certified or intended for use as a Class B device. The intention is to demonstrate how to implement the Class B libraries provided by Microchip. Further hazard and risk analysis is required to achieve Class B compliance.

DANGER: This example was developed to show how to use the Class B libraries. It is not certified for an end application. Verifying that the sensor was operating correctly without a controlled environment and access to hazardous chemicals was impossible. This application does not consider the Fault Detection Time Interval (FDTI).