Failures were all a wrong read value, and when I read the signal voltage, it was high, say for zero pressure should have been 0.5 VDC, actually was at high end near 4.5 VDC. The calibrated converted to PSI by the PIC as correspondingly high. I should have mentioned, plug in another sensor, and all normal. The 2 Freescale sensors that failed, were in service, one had been unplugged to change the PIC board (reprogrammed). The Measurement specialties was on the bench, plugged/unplugged several times to program and check PIC. Was calibrating the other sensor attached to the PIC. With the DMM in diode mode, the readings with 3 pins to each other don't seem open or shorted. Ariel Rocholl wrote: > Can you ellaborate on "3 failures". What exactly did fail? A wrong read > value? PIC reset? etc > > 2010/2/17 Carl Denk > > >> I have a pressure sensor application, where I use Integrated pressure >> sensors that have: ground, +5VDC, and signal wires. The output signal is >> in the 0 - 5 VDC range. I have had several of these of 2 manufacturers >> fail, don't know the cause, but thinking ESD might be a factor. The >> sensors are Freescale MPX5700GP, and Measurement specialties >> MSP-300-100-P-3-N-1. Failures have been both in circuit, and no >> connected. The system has been in operation for 4 years with 3 failures. >> >> Both varieties have a plastic weatherproof connector on the end of 2 >> feet pigtail cable. The pins are recessed so accidentaly touching of the >> pins not likely, though a spark could jump the 1/16" recess. The >> Measurement Specialties unit comes with a covered 3 conductor cable. The >> Freescale unit is meant for board mounting. I solder wires to the >> terminals with heat shrink over the pin/solder and the 3 wires which >> then got to the connector as above. he sensor is then potted in a >> epoxy/milled fiberglass material with a 1/4" brass close nipple for >> pressure port and a hole at the ambient port (these are gauge not >> absolute pressure units). >> >> There are the recommended capacitors on board with the PIC, I'm thinking >> more of protecting the loose sensor. >> >> The usage is natural gas, 50 PDI. max., the gas has a water vapor near >> freezing, and the water in the well is salty. >> >> I could easily add some discrete components like MOV, Diode, etc. to >> help the situation. What are suggestions. >> >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> > > > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist