Measuring the Boiling Point of Liquefied Gases Using Arduino and PhyPhox
Introduction: Measuring the Boiling Point of Liquefied Gases Using Arduino and PhyPhox
A substance that is in a liquid state is constantly evaporating or passing into the gaseous state (depending on the intermolecular forces and temperature). The pressure exerted by the gaseous molecules produced in this process is known as vapor pressure.
The vapor pressure depends on the temperature in such a way that at higher temperature higher vapor pressure. The temperature at which the vapour pressure equals atmospheric pressure is known as the boiling point.
In the case of liquefied gases contained in pressure vessels, such as gases used to clean dust, liquefied petroleum gas (LPG) or refrigerant gases, the pressure at which they are kept in the vessel allows a fraction of the gas to be in a liquid state.
If this liquid is removed from the vessel and subjected to atmospheric pressure it will begin to evaporate so it will take energy from the surrounding environment lowering the temperature around it. Under these conditions the vapour pressure of the liquid equals the atmospheric pressure and the liquid therefore reaches its boiling point.
The aim of this Instructable is to measure that boiling point, which as these are liquefied gases will normally be below 0°C, using an Arduino microprocessor and a waterproof DS18B20 temperature sensor capable of measuring temperatures up to -55°C.
The data will be transmitted via Bluetooth to a cell phone provided with the PhyPhox app that will not only allow us to graph and analyze the data but also have access to the sensors of the cell phone, in this case the barometric pressure meter, which will allow us to program the app to correct the boiling point value measured to its standard value referring to atmospheric pressure at sea level or 1 atmosphere.
The measured boiling point, in conjunction with other physical tests, e.g. 152
sound speed, can be used for preliminary identification of gaseous substances.
Supplies
* Cell Phone (Android or iOS) with barometric pressure sensor (see examples in PhyPhox Sensor DataBase).
* PhyPhox app (Google Play or AppStore).
* 1 40 ml Plastic dropper pump (Good Cook brand).
* 1 Plastic container.
* 1 Waterproof DS18B20 temperature sensor.
* 2 Breadbord mini modular.
* 1 Arduino Nano V3.0 CH340 with mini usb cable.
* 1 Bluetooth Low Energy BLE CC2541 Bluetooth 4.0 UART.
* 1 1k ohm resistance.
* 1 2k ohm resistance.
* 1 4,7k ohm resistance.
* Male/Male jumpers wire.
* Male/Female jumpers wire.
* 1 Portable battery charger (6000 mAh 3.7V, Out 5V, Output Max. 2.4A).
* Cutter knife.
* Silicone glue.
* Plastic fasteners.
Step 1: Measuring Probe
The measuring probe is basically a conical vessel that is inserted at its narrow end by the DS18B20 temperature sensor leaving enough volume of the cone to completely cover the sensor approximately 5 cm above the end of this one.
As a conical container, a plastic dropper pump (40 ml) was used that was cut into two parts, being the narrowest conical end to which the temperature sensor were adjusted and the wider conical end, next to the pump, used as a base.
The assembly fits a plastic container that serves as a support and box to hold the Arduino circuit.
The following is the procedure for constructing the measuring probe (see images):
Note: Before mounting the DS18B20 temperature sensor perform the calibration indicated in Step 2.
* Cut the plastic dropper pump to the height of the 15 ml mark (Caution: cutting hazard).
* Insert the DS18B20 temperature sensor into the narrowest conical end so that the entire metal body is inside the cone. If necessary increase the diameter of the dropper tip to adjust the sensor.
* Fix the sensor using silicone rubber or some other low temperature resistant glue. Let dry.
* Drill a hole in the wider conical base with a diameter that allows the DS18B20 temperature sensor cable to be inserted.
* Insert into the wide conical base invertedly the conical piece with the sensor inserted passing the cable through the hole previously drilled.
* Drill a hole in the lid of the plastic container that will serve as a container of the Arduino circuit of such a diameter as to allow the dropper to be inserted by its wider base.
* Attach the rubber pump to the base of the dropper, under the lid of the plastic container, so that it is fixed to it. 152