Abstract: A portable hand held instrument is capable of making accurate colorimetric measurements in the field. The instrument has a body which houses the electronic circuitry and a door which allows a vial having a solution to be measured to be placed therein. The vial is illuminated lengthwise by a light beam of two wavelengths, one of which serves as a reference. The light emerging from the top of the vial is spatially integrated and directed to a detector. The detector measures the intensity of the transmitted light, and the electronic circuit determines the difference between the logarithms of the detected signals. This difference is multiplied by a constant to produce a signal representative of the concentration and is displayed. The resolution of the measurement is automatically increased when the processor senses that the signals are too small.

Abstract: An apparatus and method are disclosed which find particular utility as a component of a traffic control system known as a conflict monitor. The apparatus includes a number of solid state switches which are activated to scan inputs from traffic control signals. The inputs are sequentially applied to a A-D converter which samples the voltage and applies it to a microprocessor which is programmed to determine the voltage and analyze the signals for conflicts, or other errors. The input lines are also connected to terminals of a program board whereby the microprocessor can instruct a switch to ground the common pin on the program board to allow program board inputs to be applied to the microprocessor for indicating permissible conflicts. A method includes a technique for determining the voltage of an input analog signal by scanning a plurality of input signals and sampling them in accordance with a relationship which provides minimum error. A display may be operated in one of two modes.