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Planning to use the following sensor:

https://shop.bb-sensors.com/Druck/Drucksensoren/

Part number SHOP 0391 0004-02M. I am planning to give 3.3 VDC to sensor. Pressure input will be 0 to 10 bar. It mentions max bridge sensitivity as 3.5 mV per V. Please someone explain what will be the output voltage range. Need to connect an amplifier to boost the output signal and give it to ADC.

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2 Answers 2

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enter image description here

hhttps://shop.bb-sensors.com/Druck/Drucksensoren/

The image from the data sheet is a little hard to read, but you will apply a voltage of up to 30 volts between +Ub and -Ub. Then you will see a voltage between S+ and S- proportional to the pressure.

3.5 mV/V is the output of the sensor for its full range (maximum value). So if you were to apply your 3.3 volts to the sensor, your maximum signal before amplification would be 3.3 volts * 3.5 mV or 11.55 mv for 10 bar.

For example, a one-bar input (10% full scale) would give an output of 1.115 mv. The two output pins are each going to be near 1/2 the supply voltage, or 1.65 volts. It will appear to be 1.651115 on S+, and 1.648885 on S- to give you your 1.115 millivolt differential voltage.

Since the each sense element's resistance is 10K, the output impedance is 5K on each of these signals, so the signals must be amplified with a high-impedance, high gain instrumentation amplifier before reading by the ADC.

enter image description here

The image comes from a TI reference design for an INA333 which is one I use. It has a good discussion of how to get an accurate reading from a strain gauge like the one you are using. See https://www.ti.com/lit/ug/tidub00/tidub00.pdf?ts=1682202573400

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  • \$\begingroup\$ John Birckhead - Hi, Please note the site rule which requires that when a post includes content (e.g. text, image, photo etc.) copied from elsewhere, that copied content must be correctly referenced. The source webpage or PDF etc. should be linked as a minimum (references for books / articles should include title, author(s), publisher, edition, page numbers etc.). Therefore please can you edit your answer to include the source links for both images. Thanks. \$\endgroup\$
    – SamGibson
    Apr 23, 2023 at 20:59
  • \$\begingroup\$ You are correct sir and I meant to add it. I have included it in an edit. \$\endgroup\$ Apr 23, 2023 at 21:31
  • \$\begingroup\$ Many thanks, John. That is one of the links added. However the link to the source of the top image is still missing. Can you please add its source reference link too? Thanks. \$\endgroup\$
    – SamGibson
    Apr 23, 2023 at 21:51
  • \$\begingroup\$ It's from the questioner's data sheet, but I added it again. Thanks for keepingme on track! \$\endgroup\$ Apr 23, 2023 at 22:21
  • \$\begingroup\$ In the datasheet it mentions that 1.5 mV / V as well. So is it like the output voltage will be in a range for a pressure input bar? My ADC is part of the FPGA..it is XADC from Xilinx. There is no PGA inside it. If the output voltage of sensor varies like then how can keep the gain of the discrete opamp based amplifier constant..how do you do calibration for this? \$\endgroup\$ Apr 24, 2023 at 9:31
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3.5mV/V means "3.5mV of differential output voltage per [1]V of excitation voltage".

So, with 3.3VDC exciting the sensor, the maximum output will be 3.5mV/V*3.3V=11.5mV differential.

High resolution sigma-delta ADCs, configured for high oversampling (slow sample rate) can often measure such voltages directly without external amplification - especially that many of them have built-in programmable gain amplifiers (PGAs) in front of the ADC.

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