GY-63_MS5611/libraries/pressure/README.md

pressure

Arduino library for pressure conversion.

Description

Simple library to convert between several pressure formats. It consists of a number of setters and getters and internally it uses millibar. In fact it just hides all conversion constants.

Pressure is implemented as a float so this limits the precision of the value.

Note: as the conversion is 2 steps the conversion error might be larger than in a single conversion step.

Note: constants need to be verified.

Interface

Constructor

• pressure(float value = 0.0) Constructor, with optional initial value.

setters

• void setMilliBar(float value) sets pressure in milliBar.
• void setBar(float value) sets pressure in bar.
• void setPSI(float value) sets pressure in PSI = Pounds per Square Inch.
• void setATM(float value) sets pressure in Atmosphere.
• void setDynes(float value) sets pressure in Dynes.
• void setInchHg(float value) sets pressure in inches mercury.
• void setInchH2O(float value) sets pressure in inches water.
• void setPascal(float value) sets pressure in Pascal. Note this is the SI unit.
• void setTORR(float value) sets pressure in TORR.
• void setCmHg(float value) sets pressure in centimetre mercury.
• void setCmH2O(float value) sets pressure in centimetre water.
• void setMSW(float value) sets pressure in Meters of Sea Water. (under water pressure unit).

getters

• float getMilliBar() returns pressure in milliBar.
• float getBar() returns pressure in bar.
• float getPSI() returns pressure in PSI = Pounds per Square Inch.
• float getATM() returns pressure in Atmosphere.
• float getDynes() returns pressure in Dynes.
• float getInchHg() returns pressure in inches mercury.
• float getInchH2O() returns pressure in inches water.
• float getPascal() returns pressure in Pascal. Note this is the SI unit.
• float getTORR() returns pressure in TORR.
• float getCmHg() returns pressure in centimetre mercury.
• float getCmH2O() returns pressure in centimetre water.
• float getMSW() returns pressure in Meters of Sea Water. (under water pressure unit).

Gas law (experimental see below)

• change(float T1, float T2, float V1 = 1, float V2 = 1, float N1 = 1, float N2 = 1) apply changing temperature (Kelvin), volume (m3) and moles. If an parameter does not change just fill in the value 1 for both before and after.

constants

The library has a number of constants to convert units. These constants can be used to write specific convertors or define specific constants.

A dedicated conversion is faster as it has only one float multiplication runtime.

inline float PSI2MSW(float value)
{
  return value * (PSI2MILLIBAR * MILLIBAR2MSW);
}

or

#define PSI2MSW     (PSI2MILLIBAR * MILLIBAR2MSW)
...
float out = in * (PSI2MSW);

Operation

pressure P;

...

P.setDynes(1000);
Serial.print("mBar: ");
Serial.println(P.getMilliBar()); // 1000 Dynes in mBar
Serial.print("TORR: ");
Serial.println(P.getTORR());     // 1000 Dynes in Torr

Obsolete

Version 0.1.0 has incorrect setters. fixed in version 0.2.0.

Experimental 0.2.1

Apply the ideal gas law : PxV / nxT = Constant

• void change(float T1, float T2, float V1, float V2, float N1, float N2)
  • T (temperature) in Kelvin,
  • V (volume) in identical units,
  • N (# atoms) in mole
• void changeT(float T1, float T2) only change temperature. T in Kelvin.
• void changeV(float V1, float V2) only change volume.
• void changeN(float N1, float N2) only change moles.

in code

pressure P;    
P.setPressure(...);
P.change(T1, T2, V1, V2, N1, N2);  // apply all changes.  
x = P.getPressure()

• do we need a changeTC(float T1, float T2) only change temperature, T in Celsius
• should functions return bool true on success ?

Kelvin = Celsius + 273.15; Kelvin = (Fahrenheit - 32) * 5 / 9 + 273.15; Kelvin = Fahrenheit * 5 / 9 + 290.93; // one operator less.

Future

• update documentation
• find a good reference for conversion formula constants.
• test with gas law.