Important points in measuring the filter pressure difference
Filter pressure difference measurement is the pressure difference between two points in a system. For filtration applications, the upstream side [A] is before the filter [B], while the downstream side [C] is after the filter. A differential pressure sensor can be used to monitor the cleanliness of a filter in liquid and gas.
how it works:
- Upstream pressure (commonly referred to as line pressure or impact pressure) directs the media through the filter. A line is installed before the filter and is also connected to the top of the sensor.
- The filter then removes contaminants from the media.
- Next, downstream pressure or effluent pressure directs fluids through the system with less pollution than in the past. In order to monitor the differential, a line is installed at the bottom of the sensor.
- When the filter is free of contaminants, the system measures the 0 differential PSI at pressure. When the filter is closed, the pressure on the downstream part decreases and causes more difference between the upper and lower parts. Using a differential pressure sensor, this unit provides a linear output signal based on the differential pressure.
Example: water purification system
A 100 PSI pump with a filter for drinking water is installed. If the downstream system pressure drops to 80 PSI, the filter must be cleaned or serviced. With 24VDC power supply, sensor and 4-20mA output signals are selected, the sensor is calibrated with 100 PSI line pressure and PSI differential pressure. When the system is operating with a clean filter, the output signal will be 4mA. As the pressure decreases downstream, the output signal increases. When the downstream pressure drops to 80 PSI, the sensor output signal reaches a full scale of 20mA. When connecting to an HMI controller, the operator knows when to replace the filter.