I am an electrical engineering student working on a project to extend a pressure transmitter with a second pressure sensor based on a TI MSP430 uC.

I am not the most experienced guy so I just want to ask if what I am doing is correct.


The job of this second sensor will be to detect a pressure change in a "part" of the transmitter which is vacumized (i.e. close to 0 bar absolute). There is no need for high precision, because if the vacumized part breaks, there will be (at least I suppose) a high pressure change, since it will be no more vacumized.

Pressure sensor specs:

  • Half-bridge strain gauge
  • Measure range 0 - 10 bar absolute
  • Nominal sensitity: 1.8 mv/V
  • Nensitivity range: 1.4 - 2.3 mv/V
  • Zero signal: ± 0.2 mV/V
  • Bridge resistance: 4 ... 7 mV/V

Since I have not much free place on the PCB (it is a very small PCB, a circle with a 28 mm radius and there are a lot of components), I cannot use a lot of components and I have to use the ADC of the MSP430 uC (10 bits). On the PCB are already for voltages:

  • 4 V digital
  • 3.3 V digital
  • 3.3 V analog

Power input circuit (already implemented):

Power input circuit

My design

My idea is to use an instrumentation amplifier (MCP6N16T-100E) with a gain of 2000 and a voltage reference of 1.024 V (MCP1501T-10E) to set as reference for the in-amp due the possibility of negative output signal of the sensor.

Schematic: Schematic

I have a few questions regarding my design:

  1. Is this a valid design for the intended purpose?
  2. Is correct to use +3V3A as supply for the sensor and +3V3D for the ICs or should I use +3V3D for everything? The MSP430 has +3V3D on DVCC and +3V3A in AVCC.
  3. Should I put more capacitors?


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