Pressure sensors

[thiagooliveira]

My demand is to identify the pressure fluctuations on the blade of a fan, the pressure measurement range is + - 1.5 kPa around the atmospheric pressure, the aquisition frequency is around 100kHz. It is desirable also the possibility to transmit the data via wireless since the passage of cables by a rotating fan would be complicated. The dimensions of the sensor are also restricted. It should have a maximum thickness of 2.5 mm.

The resolution of the sensor should be a maximum of 40 Pa.

Would like an indication of some sensor that can meet me under these conditions.

Thanks

[TomasVaverka · Accepted solution]

Thiago,

Freescale carries a complete line of silicon based pressure sensors which feature a wide range of pressures with various levels of integration on a single chip. These levels of integration start with the basic uncompensated, uncalibrated pressure sensor all the way to the fully integrated, temperature compensated, calibrated and signal conditioned pressure sensors.

The most cost effective, value added pressure sensors are the integrated pressure sensor series (MPX4000, MPX5000, MPX6000, and MPX7000). These sensors contain the transducer, temperature compensation and calibration circuitry, along with amplifier circuitry on–chip to increase the output signal for full rated pressure to typically 4.5 Volts. These sensors reduce ancillary component cost, reduces component count and simplifies system testing. The signal conditioning is accomplished by means of a four-stage amplification network, incorporating linear bipolar processing, thin-film metallization techniques, and interactive laser trimming to provide the state-of-the-art in sensor technology.

Next we have the temperature compensated and calibrated pressure sensors (MPX2000 series). These devices include the transducer plus on–chip thin film resistors/thermistors that are laser trimmed to yield a rock–solid output signal over temperature. Zero pressure offset and full–scale span are calibrated so that negligible variance will occur from device to device. Typical output at full rated pressure for these devices is 40 mVolts. Temperature compensated and calibrated sensors are very competitively priced.

The uncompensated pressure sensors are no “frills” devices. This low cost, basic sensor has incorporated just the transducer on–chip. The output will vary (within a specified range) depending on temperature. Other parameters such as zero pressure offset and full–scale span may vary from device to device (but still within a specified range). Typical output is in the 60 mVolt range with full rated pressure applied. Uncompensated sensors are at the low end of the price scale.

For your application, I would recommend considering the MPXV7002 family (-2 to 2kPa, 5V supply voltage) of integrated pressure sensors. You can connect its output directly to an input of your ADC without the need for any amplification circuitry. A 12-bit ADC cuts 5V supply into 4096 steps of ~1.22mV for each step. Considering sensitivity of 1V/kPa, the resolution is ~1.2Pa. There may be some noise, but generally you should be able to distinguish such small pressure differences.

I hope it helps.

Regards,

Tomas

[thiagooliveira]

Thank you very much Tomas,

The range and resolution of MPXV7002 family <http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MPXV7002> is great for me. But it is a differencial sensor correct? I need to measure a pressure fluctuation around the barometric pressure, that fluctuation is about 1,5 kPa around the barometric fluctuation. In other words, if we consider the barometric pressure equal to 100 kPa, I want to measure the absolute pressure range between 98,5 kPa to 101,5 kPa, do you understand?

This fluctuation is caused by a phenomenon in the flow near the fan blades. So the sensor must be thin (3 mm thickness maximum), the aquisition frequency must be about 100 kHz and it is desirable to transmit the output signal by radio (wireless).

The dimension C must be 3 mm maximum and this sensor has 12,7 mm. Can you help me?

Thank you again!

Thiago

De: Tomas Vaverka mailto:admin@community.freescale.com

Enviada em: terça-feira, 2 de julho de 2013 04:43

Para: Thiago Oliveira

Assunto: Re: Sensors - Pressure sensors

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Pressure sensors

created by Tomas Vaverka <https://community.freescale.com/people/TomasVaverka> in Sensors - View the full discussion <https://community.freescale.com/message/337911#337911>

[TomasVaverka]

Hi Thiago,

The MPXV7002 is available in both differential (MPXV7002D) and gauge (MPXV7002G) configurations. I suppose that you need a gauge pressure sensor - MPXV7002G.

If you are looking for an integrated wireless pressure sensor, we do not have a suitable solution currently available. However, it is possible to combine the MPXV7002G with our Kinetis W series MCUs or other chips such as MC12311 or MC13224V.

Regards,

Tomas