Method and apparatus for measuring air ion concentrations
AssigneeWisconsin Alumni Research Foundation
InventorJohn R. Cameron
Life of this patent
Estimating the term…
Abstract
An air ion dosimeter is disclosed which includes a small electret (10) charged to a selected level and then enclosed to await use. Measurement of air ions is made by removing the enclosure (12) from the electret (10), and either exposing the electret to the ambient atmosphere for a specific time period or drawing a specific volume of air past it. After the exposure has been made the enclosure (12) is replaced on the electret (10). The charge remaining on the electret is measured at a convenient later time. The difference between the initial charge on the electret and the charge remaining after exposure is proportional to the relative air ion concentration at the location at which the electret was exposed.
Claims14
A method of determining the relative concentration of ions in air, comprising the steps of:
- (a) providing an electret formed of a dielectric material which can carry charge;
- (b) charging the electret to a selected charge level;
- (c) covering the charged electret with an enclosure so that the electret is shielded from ambient atmosphere;
- (d) exposing the electret to ambient atmosphere for a selected period of time by removing the enclosure, and thereafter covering the electret with the enclosure again;
- (e) removing the enclosure, and, immediately thereafter,
- (f) measuring the charge remaining on the electret, the difference between the initial charge and the measured charge being related to the quantity of ions collected by the electret during exposure.
A method of determining the concentration of ions in air, comprising the steps of:
- (a) providing an electret formed of a dielectric material which can carry charge;
- (b) charging the electret to a selected charge level;
- (c) covering the charged electret with an enclosure so that the electret is shielded from ambient atmosphere;
- (d) removing the enclosure;
- (e) exposing the electret to a stream of air moving at a chosen volume rate past the electret for a chosen period of time, and thereafter covering the electret with the enclosure again;
- (f) removing the enclosure;
- and, immediately thereafter,
- (g) measuring the charge remaining on the electret, the difference between the initial charge on the electret and the measured charge being proportional to the quantity of ions collected by the electret while it was exposed to the moving stream of air.
An air ion dosimeter comprising:
- (a) an electret formed of polytetrafluoroethylene and having a cylindrical outer surface and a hollow interior bore with an electrically conductive core mounted therein;
- (b) a circular base to which the electret is mounted;
- (c) a removable enclosure for the electret electrically isolated from the conductive core within the electret including a cylindrical side wall adapted to surround the electret and mount to the base and a cap mounted to the end of the cylindrical wall to close the open end thereof.
Dependencies are inferred from the claim text.