The water pressure alert system has been used in our lab for many years. When the city water pressure is low, the system will buzz loudly, then the 24V control signal will be shut down. This alert system looks simple but very useful. It is used to protect the diffusion pump water cooling for x-ray and YAG laser water cooling system.
From last week, the alarm kept buzzing. I had to set the alarm to silent. I opened the circuit box to check today and found the problem came from the reset button. When I pushed the button, the reset could not be short. So even the water pressure sensor operated well, the 24V power could not be applied to the relay coil. The alarm was recovered after the reset button was replaced.