The multimeter features 6-1/2 digit resolution, full annunciation and simplicity of operation. Modular construction, microprocessor control, and a bus structure provide excellent flexibility. Memory programming from the front panel (or through a remote interface) controls all measurement parameters, mathematical operations and special operations. The standard hardware configuration allows for measurement of thermal true-rms volts on eight ranges and dc volts in five ranges. An averaging mode is available to automatically optimize display resolution and stability for each range in dc volts, resistance, and dc current functions. Extended resolution is also available in the ac volts function. Optional modules are available for dc current (five ranges), and resistance (eight ranges) in two-wire or four-wire arrangements. Thermal True-RMS Conversion The thermal true-rms feature allows the operator to measure the true-rms value of an ac signal at accuracies of up to .012% with a reading rate of one every six seconds. This response time compares favorably with that of existing thermal transfer standards which can take up to five minutes to complete a measurement. Modular Construction Considerable versatility is realized through unique modular construction. All active components are contained in modules which plug into a mainframe motherboard. This module-to-motherboard mating, combined with bus architecture and microprocessor control, yields ease of option selection. Microprocessor Control All modules function under direct control of a microprocessor based controller. Each module is addressed by the controller as virtual memory. Scaling factors and offset values can be applied separately, stored in memory, and automatically used as factors in all subsequent readings. Digital filtering utilizes averaged samples for each reading. Software Calibration The 8506A features microprocessor-controlled calibration of all ranges and functions. Any range can be calibrated using a reference input of any known value from 60% of range to full scale. Software calibration can be performed using front-panel or remote control, allowing recertification without opening the case or removing the multimeter from the system. Recirculating Remainder A/D Conversion The multimeter adapts Fluke’s patented recirculating remainder (R2) A/D conversion technique to microprocessor control. This combination provides fast, accurate, linear measurements and long-term stability. Options and Accessories Remote interfaces, a dc current converter, and an ohms converter are among the options and accessories available for use with the multimeter. Refer to Tables 1-1 and 1-2 for complete listings. Any one of the three Remote Interface modules (Option 05, 06, or 07) may be installed at one time,