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In the Setra Model 270 transducer manual the following instructions are given:

enter image description here

Do they mean that the excitation negative terminal should be separate with the output signal's ground? And the shield is connected to the excitation negative terminal? Is my way of wiring correct below?:

enter image description here

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A transducer of this type works best with a differential input amplifier and should preferably not be used with a single-ended input as your diagram implies. Additionally, because the case is likely to be grounded, you have possibly contravened the first requirement - that of NOT applying multiple grounds i.e. your output port is shown with a ground symbol.

If your excitation power supply is fully isolated from ground you can connect the output port negative terminal to ground. However, it will still be preferable to use a differential input if the cable-run can pick-up noise. See this: -

Best shielding against noise will be obtained by connecting the shield and negative excitation leads.

And this implies to me that you use a grounded excitation power supply and differential (balanced) input measurement amplifier.

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  • \$\begingroup\$ I use scope for now to see output. But when I common the negative excitation terminal and output signal ground the transducer does not respond anything to pressure. When I separate the excitation negative and output signal ground I get response. This is strange I dont know why. \$\endgroup\$ – atmnt Nov 12 '18 at 13:55
  • \$\begingroup\$ I use 24V sinlge power supply not bipolar supply for the excitation. \$\endgroup\$ – atmnt Nov 12 '18 at 13:56
  • \$\begingroup\$ Could you also if possible provide a diagram what you meant would be easier to follow and try. Thanks \$\endgroup\$ – atmnt Nov 12 '18 at 13:58
  • \$\begingroup\$ I'm not sure what you are wanting to see on the diagram? Are you confused by the diagrams in the data sheet for the device? Option 1 (sheet 2) is the best idea. Option 2 requires multiple isolated power supplies and this is harder to implement and is weaker in terms of noise because the output terminal is grounded and this is not preferred. Option 3 can be implemented with a differential input with signal multiplexing. Not sure what a diagram will give you. \$\endgroup\$ – Andy aka Nov 12 '18 at 14:13
  • \$\begingroup\$ I see mate, its just I dont know why the transducer does not work when I connect -Exc and -out together. The datasheet says there must be one ground but when I ground -Exc and -out it doesnt work. I thought I misunderstood the written thing. \$\endgroup\$ – atmnt Nov 12 '18 at 14:46

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