Measure Pressure

Learn:

  • Pressure Measurement

The Pressure Application Adaptor is used with the EMANT380 Bluetooth DAQ module to measure pressure. Its features are

  • 200 kPa Freescale MPX2202
  • Temperature Compensated Over 0C to +85C
  • +/-0.25% Linearity
  • Differential Configuration

The MPX2202 series device is a silicon piezoresistive pressure sensor that provides a highly accurate and linear voltage output - directly proportional to the applied pressure. The sensor is a single monolithic silicon diaphragm with the strain gage and a thin-film resistor network integrated on-chip. The chip is laser trimmed for precise span and offset calibration and temperature compensation.

The differential voltage output of the sensor is directly proportional to the differential pressure applied. The absolute sensor has a built-in reference vacuum. The output voltage will decrease as vacuum, relative to ambient, is drawn on the pressure (P1) side. The output voltage of the differential or gauge sensor increases with increasing pressure applied to the pressure (P1) side relative to the vacuum (P2) side.

With a 10V excitation, it measures from 0 TO 200 kPA (0 TO 29 psi) giving a 40 mV full scale span. The output is ratiometric when excited by voltages lower than 10V.

In our adaptor design, the sensor is excited at VEXC=3.3V. Since the excitation voltage is 3.3V, the full span output is scaled to 13.33mV. When the input of the EMANT3x0 is set to this range, the module can measure better than 1uV due to its programmable gain amplifier and the resolution of the ADC.

Thus the pressure in kPa with respect to the voltage output VO (seen at the differential input AIN4, AIN3) is given by

ρ = VO * 15000

Pressure.py

import emant import time m = emant.Emant300() m.Open("00:06:66:00:A1:D8") print m.HwId() m.ConfigAnalog(0.1,emant.Emant300.Bipolar,10) volt, binval = m.ReadAnalog(emant.Emant300.AIN3,emant.Emant300.AIN4) zero = volt for i in range(1, 10): volt, binval = m.ReadAnalog(emant.Emant300.AIN3,emant.Emant300.AIN4) kPaVal = 15000 * (volt-zero) print '%5.1f kPa' % kPaVal time.sleep(1) m.Close()

Python with EMANT380
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