The disclosed invention includes sweat sensing devices configured to periodically measure sweat conductivity and galvanic skin response, devices to measure volumetric sweat flow rate, and devices that combine the three functions. The disclosure further includes methods for using a device configured to perform periodic sweat conductivity measurements, galvanic skin response measurements, and volumetric sweat rate measurements so that each sensor modality informs composite estimates of sweat onset, sweat cessation, sweat ion concentration, and sweat rate. The method uses those measurements to inform other sweat sensing device functions, such as determining the existence of a physiological condition, or performing measurements of concentrations, ratios, and trends of sweat analytes.
