a meter is used in conjunction with a hollow , frustum - shaped disposable device to measure the concentration of an analyte in a sample of a biological fluid . the smaller end of the frustum has a porous membrane , to which a sample of the fluid may be applied . preferably , a reagent in the membrane reacts with the analyte to cause a color change . the meter has a frustum - shaped distal section that mates with the device . the meter measures the color change and computes from the change the analyte concentration in the sample . the meter and disposable device permit remote dosing of the device , which minimizes the likelihood of cross - contamination between the user and the meter . devices can be mounted on the meter and released from the meter without touching them , to further protect against contamination .