Fluke 5725A instruction manual Power Supply Assembly A4

Models: 5725A

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4-16. Power Supply Assembly (A4)

5725A

Instruction Manual

4-16. Power Supply Assembly (A4)

The Power Supply assembly (A4) provides regulated system supplies for all 5725A assemblies except as noted below, as well as unregulated fan supply and high voltage supplies for the High Voltage Amplifier. The assembly also includes microprocessor- controlled switching and an independent current-limit circuit.

Note

Other power supplies are contained on the Current Amplifier assembly (A2). The A2 assembly includes a high-current supply and a local ±20V supply.

The Power Supply assembly has four sections: high voltage supply, switching, current limit, and system supply section. Each section is first briefly described, then described in detail.

High Voltage Supply Section

The high voltage supply section consists of a simple unregulated power supply with the additional capability of being run at ±400V dc for normal instrument operation, or at ±50V dc for troubleshooting.

Switching Section

The switching section behaves like an electronic DPST switch, which by command of the microprocessor or the current-limit section, shuts down the high voltage supplies. Microprocessor control alone can turn on the high voltage supplies in normal operation. At the board level, manual control of the switch is possible to enable stand-alone turn on of the Power Supply assembly (A4) and the High Voltage Amplifier assembly (A3).

Current-Limit Section

The current-limit section shuts down the high voltage supply in a latching mode if excessive current is drawn by the High Voltage Amplifier or if the ±15V or +5V supplies fail. This section of the Power Supply assembly consists of a pair of shunts, a pair of comparators, and a system supply monitor.

System Supply Section

The system supply section contains various regulated power supplies, and is comprised of five linear regulators. In addition, the system supply section contains an unregulated supply for the fan.

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Fluke 5725A instruction manual Power Supply Assembly A4