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Measuring Relative Humidity / Pressure using PSoC1

Last Updated: March 24, 2012

How to measure environmental variables like Relative Humidity or Pressure using PSoC1?



Physical quantities like Humidity, Temperature, and Pressure are often monitored to get information about the environmental conditions. Various sensors are capable of measuring these quantities and providing an output in the form of an analog value. Humidity sensors are widely used in applications like weather forecasting, air conditioners, Hygrometers etc. Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude and make an integral part of various types of instrumentation.

Two example projects (combined in the zip file) are given below, which illustrate how PSoC 1 can be used to measure relative humidity and pressure.

Project#1 measures the relative humidity level using CY8C29466 device. It is interfaced with the HIH-4031 humidity sensor, which provides an analog voltage output corresponding to the humidity level. The voltage from the sensor is fed to an analog to digital converter (ADCINC12) user module through PSoC internal programmable gain amplifier (PGA), which is configured as a buffer. The relative humidity (RH) value is calculated in percentage and is displayed on the LCD.

Project#2 measures the pressure sensed by a MPXM2102A sensorusing CY8C29466 device.The MPXM2102A pressure sensor provides the differential analog voltage corresponding to the pressure applied. This value is amplified by the Instrumentation Amplifier and is then measured by ADCINCVR usermodule to calculate the pressure level. The sensor ouput ranges from 0 kPa to 100 kPa. The sensed value is displayed on an LCD.

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