Digital Programming Interfaces for Analog-controlled Power Supplies
Analog-programmable power supplies are easily controlled by the d-c voltage generated by a digital to analog converter (DAC). Because Kepco's operationally programmable models have a uniform 0-10 volt, 0-1 mA input, it is possible to design DACs to be able to control all such models.
Kepco's ANALOG PROGRAMMABLE power supplies, notably the operationally programmable models, ATE, BOP and JQE may be interfaced to the IEEE 488 instrumentation bus through a variety of interfaces which function as digital to analog converters. The interfaces implement the AH1 acceptor handshake and L1 listener plus listener-only functions of the IEEE 488 protocol. The interfaces differ mainly in their mechanical aspects and in the number of control channels that are offered. The BOP also accept a talker-listener GPIB card, either BIT 4882 (12-bit) or BIT 4886 (16-bit) which support the SCPI language.
Kepco models with built-in digital capabilities, the ABC, BOP High Power, BHK-MG, MAT and MST series, do not require these digital to analog programming interfaces. The ABC, BOP High Power BHK-MG, MAT and MST implement both talker and listener functions. Analog programmable models should be used when your application requires analog modeling of a process or simulation or modulation. Except for the BOP High Power and JQE, Kepco's operationally-programmable instruments offer high speed control capabilities that allow for rapid slewing and high-frequency modulation. When used with a digital interface, the relatively slow speed of the computational process will not allow full exploitation of the high speed capability, but they retain the ability to have audio spectrum modulation superim- posed on the digitally programmed d-c values. The Kepco SN series of external digital to analog converters provide listen-only digital capabilities for JQE and ATE power supplies.
An interface card called BIT plugs into an internal slot in the low power low-voltage BOP models (models up to ±200 volts, up to 400 watts).
Kepco's ABC, BOP High Power and BHK-MG power supplies are digitally programmed power supplies with built-in GPIB (IEEE 488.2) interfaces. The BHK-MG, to retain backwards compatibility with earlier BHK high voltage models, contains provision for both analog and digital control.
INPUT DATA FORMAT
The SN and BIT interfaces accept data in either hexa- decimal form with a 12-bit binary resolution of 1/212 = 1/4095 or 0.0244%, or in Binary Coded Decimal (BCD) format with a 3-digit resolution of 1/103 = 1/999 or 0.1%. In both instances, the host sends character strings to control channel selection, range, polarity and data as a percent of full scale.
VXI, the "instrument on a card" concept, was developed for signal control and measuring instruments. It has achieved a substantial following in the test and measure- ments field. Unfortunately, power supplies are not like signal-level instruments in that they create substantial amounts of heat. This is especially true of instrumentation- type programmable power supplies which use linear, dissipative control techniques. Such heat dissipation is not compatible with VXI card cages.
To prevent the heat generated by power supplies from affecting other elements in a VXI card cage, and to minimize the d-c voltage drop between the power supply and its load, we recommend that the power supplies be located close to the load.
To provide VXI support, Kepco offers a single-width, size "C"" card to plug into a VXI cabinet and provide an output to the Kepco single address, multiple instrument bus. Models in the MAT, MST, BOP High Power and BOP-TMA lines can directly interface with this card and through it, with other VXI instruments. The power supply's dissipators are remote from the VXI cage so their heat will not interfere with the proper operation of the other instruments in the cage.
KEPCO, INC. • 131-38 SANFORD AVENUE •
FLUSHING, NY. 11355 U.S.A.
TEL (718) 461-7000 • FAX (718) 767-1102
www.kepcopower.com • email: firstname.lastname@example.org