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183 lines
5.9 KiB
Markdown
183 lines
5.9 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/pressure/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/pressure/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/pressure/blob/master/LICENSE)
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[](https://github.com/RobTillaart/pressure/releases)
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# pressure
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Arduino library for pressure conversion.
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## Description
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Simple library to convert between several pressure formats.
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It consists of a number of setters and getters and internally it uses millibar.
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In fact it just hides all conversion constants.
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Pressure is implemented as a float so this limits the precision of the value.
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If other constants / conversions are needed please open an issue on GitHub.
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Note: as a conversion uses two steps the conversion error might be (bit) larger
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than in a single conversion step as there are two multiplications involved.
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Note: constants need to be verified.
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## Interface
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#### Constructor
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- **pressure(float value = 0.0)** Constructor, with optional initial value.
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#### Setters
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- **void setMilliBar(float value)** sets pressure in milliBar.
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- **void setBar(float value)** sets pressure in bar.
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- **void setPSI(float value)** sets pressure in PSI = Pounds per Square Inch.
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- **void setATM(float value)** sets pressure in Atmosphere.
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- **void setDynes(float value)** sets pressure in Dynes.
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- **void setInchHg(float value)** sets pressure in inches mercury.
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- **void setInchH2O(float value)** sets pressure in inches water.
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- **void setPascal(float value)** sets pressure in Pascal. Note this is the **SI** unit.
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- **void setTORR(float value)** sets pressure in TORR.
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- **void setCmHg(float value)** sets pressure in centimetre mercury.
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- **void setCmH2O(float value)** sets pressure in centimetre water.
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- **void setMSW(float value)** sets pressure in Meters of Sea Water. (under water pressure unit).
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#### Getters
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- **float getMilliBar()** returns pressure in milliBar.
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- **float getBar()** returns pressure in bar.
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- **float getPSI()** returns pressure in PSI = Pounds per Square Inch.
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- **float getATM()** returns pressure in Atmosphere.
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- **float getDynes()** returns pressure in Dynes.
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- **float getInchHg()** returns pressure in inches mercury.
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- **float getInchH2O()** returns pressure in inches water.
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- **float getPascal()** returns pressure in Pascal. Note this is the **SI** unit.
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- **float getTORR()** returns pressure in TORR.
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- **float getCmHg()** returns pressure in centimetre mercury.
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- **float getCmH2O()** returns pressure in centimetre water.
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- **float getMSW()** returns pressure in Meters of Sea Water. (under water pressure unit).
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#### Gas law (experimental see below)
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The **change()** function is applied to the current internal pressure.
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- **void change(float T1, float T2, float V1, float V2, float N1, float N2)**
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- apply changing temperature (**Kelvin**),
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- volume (m3) and moles.
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- If an parameter does not change fill in 1 for both before (T1,V1, N1) and after (T2,V2,n2).
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- **void changeT(float T1, float T2)** only change temperature. T in **Kelvin**.
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- **void changeV(float V1, float V2)** only change volume.
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- **void changeN(float N1, float N2)** only change moles.
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#### Constants
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The library has a number of constants to convert units. See the pressure.h file.
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These constants can be used to write specific convertors or define specific constants.
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A dedicated conversion is faster as it has only one float multiplication runtime.
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```cpp
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inline float PSI2MSW(float value)
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{
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return value * (PSI2MILLIBAR * MILLIBAR2MSW);
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}
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```
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or
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```cpp
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#define PSI2MSW (PSI2MILLIBAR * MILLIBAR2MSW)
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...
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float out = in * (PSI2MSW);
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```
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## Operation
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```cpp
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pressure P;
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...
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P.setDynes(1000);
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Serial.print("mBar: ");
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Serial.println(P.getMilliBar()); // 1000 Dynes in mBar
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Serial.print("TORR: ");
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Serial.println(P.getTORR()); // 1000 Dynes in Torr
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```
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#### Obsolete
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Version 0.1.0 has incorrect setters. fixed in version 0.2.0.
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#### Experimental 0.2.1
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Apply the ideal gas law : **P x V / n x T = Constant**
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- **void change(float T1, float T2, float V1, float V2, float N1, float N2)**
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- T (temperature) in Kelvin,
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- V (volume) in identical units,
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- N (# atoms) in mole
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- **void changeT(float T1, float T2)** only change temperature. T in Kelvin.
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- **void changeV(float V1, float V2)** only change volume.
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- **void changeN(float N1, float N2)** only change moles.
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in code
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```cpp
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pressure P;
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P.setPressure(...);
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P.change(T1, T2, V1, V2, N1, N2); // apply all changes.
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x = P.getPressure()
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```
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- do we need a **changeTC(float T1, float T2)** only change temperature, T in Celsius
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- should functions return bool true on success ?
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```cpp
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Kelvin = Celsius + 273.15;
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Kelvin = (Fahrenheit - 32) \* 5 / 9 + 273.15;
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Kelvin = Fahrenheit \* 5 / 9 + 290.93; // one operator less.
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```
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## Future
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#### must
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- update documentation
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- find a good reference for conversion formula constants.
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#### should
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- test with gas law.
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- calculate getter constants from setter constants. 1.0 / XXX
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- rename parameters so they make more sense?
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```
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void setMilliBar(float milliBar ) { _pressure = milliBar; };
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void setBar(float Bar) { _pressure = Bar * BAR2MILLIBAR; };
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void setPSI(float PSI) { _pressure = PSI * PSI2MILLIBAR; };
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```
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#### could
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- defaults for functions? 0 like constructor?
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- move code to .cpp file ?
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- change could return int indicating
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- 1: a change is made.
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- 0: no change is made
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- -1: parameter negative
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- change could return a float indicating the new pressure in mBar?
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