Student Spirometer 2
The Spirometer housing is made of heavy transparent plastic 6mm / 6.5mm thick. It measure 300 x 375 x 375mm overall ( 12 x 15 x 15 inch )
The 9 liter gas holder is made of light transparent plastic, and carries two needle points rest in metal dimples and serve as the pivot points for the gas holder.
The counterweight is free to move for adjustment on a Counter poise arm and, when adjusted, is locked in Place.
On the side corner of the gas holder there is a scale 130mm long (5 1/4 in). Graduated from 0 to 9 liters in 0.1liter increments. This scale is read by a metal point that can be adjusted for zero. This corner of the gas holder also carries a mounting for a writing pointer that can be used with a Kymograph or Chart Recorder.
The water chamber for sealing the gas holder has been reduced to the minimum capacity that allows easy clearance for the gas holder for the gas holder, and has a drain in its base with tubing and a plug.
The 30mm bore tubing for the airways, which is made of low density polythene, is light and strong. This tubing has extremely low- profile annular rings, which offers the minimum distortion on bending and therefore preserves the maximum cross-section area.
The mouthpiece is made of moulded soft rubber. It fits behind the lips, and has two soft rubber bites to locate the teeth and make it more comfortable for breathing through the mouth. The noseclip is also constructed of soft moulded rubber.
This instrument is supplied with a one-way valve that fits onto the mouthpiece. This valve ensures that the gas stream flows only in one direction. On inspiration, one valve opens and the other one closes, and vice versa on expiration. The valves are a new design and consist of thin mica discs mounted in cast plastic frame.
The mica disc is held at its center by a nickel plated brass threaded shank that has a soft stainless steel spring mounted on it. The mica disc moves against this soft spring and opens with the slightest positive pressure. It locks with slightest negative pressure.
The mouthpiece and tubing assembling fits to a tubing valve that is mounted in the side of the spirometer base. This tubing valve can be used for either an open or closed circuit. It has tubing attachments for one or two tubes on both the back and the front. It also has two ports to atmosphere. When the rotating handle is down, the mouthpiece tube or tubes are vented to the atmosphere. When the handle is rotated up, the mouthpiece circuit is connected into the spirometer circuit. This not only allows the subject to become accustomed to the apparatus with the tubing vented to atmosphere, but also allows an exact starting time to be determined for the experiment.
The soda lime canister is made of transparent plastic, and can therefore be used with a color indicating absorbent. The canister is 80mm in diameter x 125mm in length (3 ¼ x 5 in), and has a capacity of 600 ml. it mounts on a metal plate at the back of the spirometer, and can be connected in or out of the circuit by changing only one hose.