California Instruments’ Model 847T Precision Programmable Oscillator is designed to plug into and obtain power from all of the Invertron· AC Power Sources. Frequency and amplitude are remotely programmable through an IEEE-488 Interface connector or through a parallel interface connector. Both connectors are mounted on the rear of the associated power source and connected to the 847T through a multi-conductor cable. Parallel programming by the parallel interface connector of the 847T is always available when the GPIB relinquishes control or allows the system to go the local control mode. If the 847T GPIB interface is enabled, the parallel interface input at the 846CM is disabled. The output of the Model 847T provides three- phase variable frequency and amplitude drive for the power source. Remote inputs sense the voltage across the load connected to each leg of the power source. In response to the level of these inputs, the servo systems adjust the individual outputs of the 847T to maintain the voltage across the power source load at the programmed value. The 847T employs digital logic techniques for frequency generation with a crystal controlled oscillator serving as the reference for the digital logic circuits. This technique provides long-term frequency stability not obtainable with analog circuits. The 847T is capable of operating from 45 Hz to 9999 Hz over three ranges; 45 to 99.99 Hz (selectable in 0.01 Hz steps), 45 to 999.9 Hz (selectable in 0.1 Hz steps) and 45 to 9999 Hz (selectable in 1 Hz steps). The low end of the frequency detector is adjusted to shut down the output of the 847T when the selected frequency is below 45 Hz. The high end is factory adjusted to the upper limit of the associated power source. Extending the frequency range beyond 5 KHz requires programming with an internal jumper. A "soft start" feature is incorporated which gradually increases the output amplitude at initial turn-on and when operation resumes after a shut down caused by programming an out-of-limit frequency. The output voltage range of the oscillator is proportional to the amplitude programmed for the associated power source. When the programmed output voltage for the power source is 135 or 270 volts, the oscillator output will be in the range of 4 to 5 volts rms. The precise level will be dependent upon the voltage level at the sense input. The sense input, when connected directly across the load, increases the oscillator output (and the power source output) to compensate for any drop in the lines connecting the power source to the load. Relative to the reference phase, Phase A, the angle of the Phase C output may be internally preset to any thirty degree increment. Because of the digital techniques employed, the electrical angle between phases remains constant irrespective of frequency.