3.7.4 Experimental procedures
1)Experimental processing
(1)Connect the circuit of the instrument according to the requirements.Use Forton barometer to measure atmospheric pressure p0 and the mercury thermometer to measure ambient temperature T0.Turn on the power to preheat the electronic instrument for 20 minutes.Zero the voltmeter display of pressure measurement.
(2)Close valve C2 and open valve C1,and slowly pump the air into the container bottle with the inflating ball.Measure the pressure and temperature of the air in the bottle with the pressure sensor and AD590 temperature sensor,and record the pressure p1 and temperature T0 when the pressure in the bottle is uniform and stable.
(3)Suddenly open valve C2 to release the air from the bottle to the ambient atmospheric.Then,close C2 immediately when the air pressure in the bottle drops to the ambient atmospheric pressure p0.
(4)When the temperature of the air in the cylinder rises to the room temperature T0,record the pressure p2 of the gas in the bottle.
(5)Convert the measured pressure values p0,p1 and p2(in mV)into kPa or Pa,and put them into Equation(3.7.4).The adiabatic index of air can be obtained,and repeat four times to get the average value.(https://www.daowen.com)
2)Tips and Attentions
(1)The semiconductor pressure sensor has a certain working range.When pumping the air into the bottle during the experiment,attention should be paid to the reading of the voltmeter connected with the pressure sensor.
(2)Do not make mistake between the positive and the negative electrodes of AD590.
(3)Do not press the silicon pressure sensor by hand during the experiment.
(4)If there is air leakage at the connection part between the rubber stopper and glass bottle or glass tube,704 silica gel can be used to prevent air leakage.
