Hey all,
I am running response time tests on valves, time from actuation until pressure reaches 90% of maximum. I am using an scxi 1120 with 1327 and t type thermocouples to acquire and record the temperature, which works fine. An scxi 1121 with 1327 is connected to my pressure transducers, which also works correctly in MAX. My last module is an scxi 1161, used for triggers. The triggers operate correctly and successfully cycle the valves. I am using virtual channels for both the thermocouples and the pressure transducers because I am running an older version of labview (7) and found it easier to map ranges than apply a custom scale to the waveform. Both in MAX and labview the temperature and pressures read correctly from their starting values. However, after a few cycles the pressures that should be alternating from 100 to zero simply hover around 5 and do not seem to change much. The thermocouples continue to read correctly, but the pressure transducers appear to loose their scaling. This problem does not occur regularly, after a set number of cycles, but rather randomly (2-10 cycles). Also sometimes only one transducer at a time will get out of scale, other times both transducers will stop working at once. I first noticed this problem after switching from hardware channels with custom scaling in labview, to virtual channels (from MAX) where the ranges were pre-mapped (no scaling in labview). Is this some sort of interference or grounding issue? Any help or advice will be appreciated, thanks in advance.
-Sean K
