Abstract: Methods are disclosed for scaling and calibrating predetermined signals in apparatus for measuring and displaying predetermined characteristics of reciprocating machines. In the preferred embodiment, the methods comprise the calibrating of a pressure data acquisition and scaling system to eliminate inaccuracies due to temperature related changes in component values due to such things as component aging, the scaling of an amplified signal from a pressure transducer suitable for display purposes and the cancelling of an amplified output signal from the pressure transducer when zero pressure is applied thereto.

Abstract: Apparatus and method are disclosed for measuring and displaying predetermined characteristics of reciprocating piston machines. In the preferred embodiment, the predetermined characteristics comprise indicated horsepower, crankshaft angle and piston position. The apparatus comprises a central processing unit, memory devices, keyboard assembly, display controller, display unit, sweep generator, pressure data acquisition and scaling system, shaft encoder and pressure transducer operatively connected by an address bus and a data bus to measure and display the predetermined characteristics. A method is provided whereby an electrical signal is generated which is proportional to the instantaneous position of a designated piston in the reciprocating piston machine.