Flow Switch Stops False Alarms In Dialysis Machine

A piston-type flow switch warns patients on dialysis machines of interruptions in flow. The magnetic piston in the new FS-W switch from Gem Sensors Inc. in Plainville, Conn., moves in response to flow and actuates a hermetically sealed reed switch isolated within the plastic body. A stainless-steel spring deactivates the switch when flow decreases. The switch gives users positive flow and no flow indications to accurately identify any interruption of flow during dialysis. The previous switch, a thermal-dispersion flow sensor, was a source of maintenance problems and high repair costs. The sensor couldn't accurately detect fluid flow, caused unwarranted alarms, and eventually shut down the machine.