Abstract: A substantially non-loading circuit for measuring voltages in a range with relatively high upper limit uses a resistive voltage divider for scaling down these voltages for application to a digital voltmeter capable of measuring voltages in a range with relatively low upper limit. The loading that the input circuit of the resistive potential divider would place on the circuit being measured is reduced by placing the loading of the potential divider input circuit on an electrically adjustable voltage supply, rather than the circuit being measured. The current loading on the circuit being measured is sensed; and the output voltage of this supply is automatically adjusted by feedback to reduce the sensed circuit. In this way, loading of the circuit being measured is reduced, thus avoiding undesirable reduction of the voltage across the circuit owing to its being loaded.

Abstract: A color test pattern, such as a crosshatch line pattern, is generated on the phosphor screen of a color cathode ray tube or a color kinescope. A cathode ray tube display error measuring device comprising at least two optical plates, each transmissive to the light emitted by a different color phosphor of the color kinescope is placed adjacent the phosphor screen. One of the optical plates is rotated until the two images of the test pattern formed by the two plates move into alignment with each other. The amount of rotation is a measure of the amount of error present.