Fluke 5720A service manual Functional Description Presented by Output Function

5700A/5720A Series II Calibrator

Service Manual

These analog assemblies are interfaced to the Analog Motherboard assembly (A3). The guarded digital bus generated by the guard crossing portion of the Regulator/Guard Crossing assembly controls all analog assemblies except the Filter/PA Supply. The Guard Crossing interfaces with the unguarded CPU assembly via a fiber-optic link. The Transformer assembly, along with the filter portion of the Filter/PA Supply assembly and the regulator portion of the Regulator/Guard Crossing assembly, create the system power supply for all the analog assemblies. The Power Amplifier Supply portion of the Filter/PA Supply assembly provides the high voltage power supplies required by the Power Amplifier assembly. The amplitudes of these high voltage supplies are controlled by circuitry contained on the Power Amplifier assembly.

Figures 2-2 and 2-3 are block diagrams for the analog section of the Calibrator.

2-9. Functional Description Presented by Output Function

This part of the theory section presents Calibrator operation from the perspective of each output function. It describes which assemblies come into play, and how they interact. It does not provide a detailed circuit description. Refer to the individual assembly theories further on in this section for detailed circuit descriptions.

2-10. DC Voltage Functional Description

The DAC assembly (A11) provides a stable dc voltage and is the basic building block of the Calibrator. DC voltages are generated in six ranges:

∙220 mV

∙2.2V

∙11V

∙22V

∙220V

∙1100V

The 11V and 22V ranges are generated by the DAC assembly, with its output, DAC OUT HI and DAC SENSE HI routed to the Switch Matrix assembly, where relays connect it to INT OUT HI and INT SENSE HI. Lines INT OUT HI and INT SENSE HI connect to the Calibrator binding posts by relays on the Analog Motherboard assembly (A3).

The 2.2V range is created on the Switch Matrix assembly by resistively dividing by five the 11V range from the DAC assembly. Relays on the Switch Matrix and Analog Motherboard route the 2.2V range output to the Calibrator binding posts.

The 220 mV range is an extension of the 2.2V range. The Switch Matrix assembly resistively divides by ten the 2.2V range to create the 220 mV range. Relays on the Switch Matrix and Analog Motherboard route the 220 mV range output to the front panel binding posts.

The 220V range is generated by the DAC and Power Amplifier assemblies. The Power Amplifier amplifies the 11V range of the DAC assembly by a gain of -20 to create the 220V range. The output of the Power Amplifier is routed to the High Voltage Control assembly (A14), where a relay connects it to PA OUT DC. Line PA OUT DC is routed to the binding posts via relays on the Switch Matrix and Analog Motherboard.

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