I am trying to connect a combined pressure transducer and temperature indicator to a DAQ system by Dewesoft and this sensor has two available wiring configurations available, 3 wire and 4 wire. I'm unable to understand the difference between these two according to its circuit diagram and what is the significance of each.

Which configuration would be more suitable if I want to reduce the number of output channels from the sensor to the DAQ, or will the number of outputs remain the same despite its configuration.

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(Link to the sensor spec sheet: https://www.pmc1.com/Customer-Content/www/Products/Files/ATM.1st.T.705a.pdf)

This is similar to another question that I have previously asked, but in this question, I want to figure out how the wiring actually works. Thanks!

  • 2
    \$\begingroup\$ Possible duplicate of Need advice choosing wiring configuration for combination pressure and temperature sensor \$\endgroup\$
    – Transistor
    Jul 21, 2019 at 23:51
  • \$\begingroup\$ start with the top schematic ... remove the pressure transducer from the circuit ... look at the resulting circuit ... how does it compare to the bottom circuit? \$\endgroup\$
    – jsotola
    Jul 22, 2019 at 0:01
  • \$\begingroup\$ @jsotola If I remove the transducer, then it would look like the independent temperature sensor circuit in the bottom diagram \$\endgroup\$ Jul 22, 2019 at 0:16
  • \$\begingroup\$ exactly ... that illustrates the difference in the circuits ... it is unclear what your actual question is ... i think that you may be expecting the circuits to be more complicated than they actually are \$\endgroup\$
    – jsotola
    Jul 22, 2019 at 0:35
  • \$\begingroup\$ yeah, I think I have figured it out, thanks for the help \$\endgroup\$ Jul 22, 2019 at 0:39

1 Answer 1


Looks to me like they are just saying, if you so choose, you may supply power to the two transducers from separate (isolated) power supplies. I'm guessing that would be a favorable approach if you wanted to ensure that the noise in the measurement from the transducers was independent and not coupled through the power source. But then, of course, you need two independent power sources to make that happen, which is not so difficult if we're talking about battery subsystems. Somewhat trickier if we're talking about AC/DC converters.

You would need to experiment to determine your sensitivity in both measurements was "good enough" using a single power source.


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