I have purchased five of your sensors, 2 MPXV5050V, 1 MPXV4115V, and 2 MPXV6115V (not delivered yet). The first three of the five have failed after working for awhile. They have been mounted on a small pcb sold by Modern Devices. I have followed the recommended circuit in Fig. 4 on your data sheet (for the first 3--there are some changes to Fig. 4 for the MPXV6115V). I have checked the power supply and it is operating at a steady +5V. The sensors worked great for awhile. They are feeding analog input to a NUMATO USB breakout board. Based on the pressure, the GPIOs on the board are set to turn a vacuum pump motor on or off and to control some solenoid valves.
My question is: Does the sensor mounting orientation affect the life of the sensors? I have them mounted on a vertical surface of an enclosure (the little pipe that connects to tubing is horizontal). I am grasping at straws. I thought maybe the gel inside the sensor was flowing away from whatever it is protecting. The total time that the sensors were used before they failed was less an 8 hours but they have been mounted as described for weeks. I need to solve this or find a different sensor. Any ideas?