FOUR-WIRE BUS FOR INSTRUMENT SELF-TEST
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-17
To improve instrument reliability and serviceability, an electronic instrument's internal microprocessor measuring system may also be used to monitor the internal condition of the instrument itself. While techniques such as CRC checks, watchdog timers, loopbacks, and various test algorithms can be employed to ensure proper operation of the microprocessor and its support logic, little methodology has been applied to the monitoring of the signal condi- tioning circuitry ahead of the analog-to-digital converter (ADC). In the past, test points have been included in designs for self-test, but generally there are too few to be truly indicative of the overall "health" of the system. The pro- posed 4-wire bus configuration of Figure 1 is a simple and economical test interface for gaining access to multiple test points within the analog sections of an instrument. When incorporated into the design of the product, the bus provides greatly improved self-test capability, and assists in factory test operations.