A testing system for testing a chemical characteristic of an aqueous solution, the system comprising: a portable, hand-held instrument comprising a housing; a display on the housing; a slot formed in the housing at an outer surface thereof; a test element placement member attached to the housing and defining a central surface of the slot, with the slot and test element placement member defining a test element receiving port; a test element comprising a substrate supporting at least one test pad (30; 32; 34) responsive in color to the chemical characteristic of the aqueous solution wetting the test pad, the test element configured for receipt within the test element receiving port with the at least one test pad disposed against the test element placement member and with the substrate covering the at least one test pad within the slot; a color detector for detecting the color of the at least one test pad, the color detector comprising a light generating element (42 1; 42 2; 42 3) and a light receiving element (44 1; 44 2; 44 3) disposed within the housing to direct light from the light generating element, through the test element placement member, to be reflected from the at least one test pad in response to the color of the test pad, back through the test element placement member and onto the light receiving element; circuitry disposed within the housing and associated with the light receiving element for determining the chemical characteristic of the aqueous solution in response to the reflected light received by the light receiving element; and the display being associated with the circuitry and displaying an indication responsive to the determined chemical characteristic of the aqueous solution; the test element placement member effective to isolate the circuitry from the aqueous solution wetting the test pad while permitting the generated light to pass out of the housing and the reflected light to pass back into the housing; characterized in that the test element placement member closes the slot and in that the substrate is opaque and the substrate's surface supporting the at least one test pad is non-reflective. a portable, hand-held instrument comprising a housing; a display on the housing; a slot formed in the housing at an outer surface thereof; a test element placement member attached to the housing and defining a central surface of the slot, with the slot and test element placement member defining a test element receiving port; a test element comprising a substrate supporting at least one test pad (30; 32; 34) responsive in color to the chemical characteristic of the aqueous solution wetting the test pad, the test element configured for receipt within the test element receiving port with the at least one test pad disposed against the test element placement member and with the substrate covering the at least one test pad within the slot; a color detector for detecting the color of the at least one test pad, the color detector comprising a light generating element (42 1; 42 2; 42 3) and a light receiving element (44 1; 44 2; 44 3) disposed within the housing to direct light from the light generating element, through the test element placement member, to be reflected from the at least one test pad in response to the color of the test pad, back through the test element placement member and onto the light receiving element; circuitry disposed within the housing and associated with the light receiving element for determining the chemical characteristic of the aqueous solution in response to the reflected light received by the light receiving element; and the display being associated with the circuitry and displaying an indication responsive to the determined chemical characteristic of the aqueous solution; the test element placement member effective to isolate the circuitry from the aqueous solution wetting the test pad while permitting the generated light to pass out of the housing and the reflected light to pass back into the housing; characterized in that the test element placement member closes the slot and in that the substrate is opaque and the substrate's surface supporting the at least one test pad is non-reflective.