Simultaneous measurement of pressure, temperature, and conductivity with counters

Modular sensors of pressure, temperature, and conductivity with frequency outputs can be simultaneously sampled with counters. Power for the counters is inconsequential and there is no serious limit for counting period. Many sensors can be sampled simultaneously by simply adding counters. This is an old technique but complex sensing packages with low power, modular, frequency output sensors make it an attractive one. The number of stages of the counter, the stability of the sample interval, and the clocking of the serial shift register that moves the count to the logger are important considerations. Sample clock instabilities or timing errors must be detected and corrected and lost high order bits due to overscaling of the counters must be restored. With these considerations, modular frequency output sensors can be added to an underwater system for an incremental cost of one electrical penetration per sensor