Abstract: A two-terminal multimeter capable of both volt/ohm and current measurement employs an input protection circuit with a positive temperature coefficient impedance and a reference impedance, across which an A-D converter takes measurements. A current measurement signal activates a switch to ground one side of the reference impedance for taking current measurements. A controllable clamping switch grounds the positive temperature coefficient impedance in an input overload situation to provide input protection against damage to the meter components.

Abstract: A method of displaying continuously acquired measurement data in a display with a fixed number of pixels is provided. Measurement data is provided at a predetermined fixed sample rate independent of a pixel rate which is equal to or less than the sample rate. The measurement data is convened to pixel data which includes the minimum, maximum, and the average of the measurement data gathered and the pixel data is plotted to the pixels at a pixel rate. At the end of the fixed number of pixels of the display, the pixel values are compressed to half the fixed number of pixels and the pixel rate is halved, thereby doubling the time scale. This process can continue indefinitely, requiring no operator intervention or prior knowledge to set a total measurement time. Furthermore, the sample rate is independent of the pixel rate so that a tradeoff of sample rate and total measurement time need not be made.

Abstract: A multi-function, multi-mode switch for an instrument that changes the instrument between primary and secondary functions and between first and second modes of operation within the primary and secondary functions. The instrument changes from the first mode of operation to the second mode of operation when the switch is actuated for a first period of time. The instrument changes from the second mode of operation to the first mode of operation when the switch is activated for a second period of time. The instrument changes between the primary and secondary functions when the switch is operated for a third period of time. The switch controls a program that instructs the instrument to perform the appropriate operations. The program also instructs the instrument to confirm that an operation has occurred via audible and visual feedback.