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Although developed primarily for use in digital plethysmography and the study of peripheral circulation, the PT5 Pressure Transducer can be used for recording of other physiological variables involving volumes and low pressures. It can be used to measure absolute or differential pressures and with pneumotachographs to obtain respiratory flow patterns.

The design emphasis of the PT5 is directed toward measuring volume with small changes of pressures in the system. Note that this is the opposite of gages designed to measure vascular pressure where it is desired to measure pressure with the least volume change. Neither ideal is reached but errors tend to be negligible if the proper gage is chosen. It is not possible to measure volume dynamically without the use of a slight pressure, but since the PT5 has high sensitivity at low pressures, it is ideal for this purpose.

Combining a pneuomotachograph with the PT5 and a DC amplifier, Model LP122, P122/CP122 or with the 15A12 in the Model 15 series provides analog respiratory flow signals. Using PolyVIEW data acquisition, integration of the flow signal will provide precise respiratory volume data.

The PT5 consists of two cavities separated by a large sensitive diaphram which actuates a cantilever on which bonded strain gages transduce changes in movement to changes in resistance.

Access to both cavities is accomplished by ports which accept both standard Luer fittings and the volume calibrators. The movement is very rugged and will withstand much abuse. It is free from the microphonics and fragility of unbonded gages.

Liquid should never be used in the cavity adjacent to the connector, since this houses the strain gage elements. However, liquid may be used in the lower chamber.

Maximum working volume, mm³