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General Information14
The HP-IB board also processes measurement and status data received from the output boards. This data may be read back
over the HP-IB and/or displayed on the supply's front panel.
The power supply has no potentiometers. Each output is individually calibrated over the HP-IB using calibration
commands (see Appendix A). Correction factors are calculated by the power supply during calibration and are stored in a
non-volatile memory which is located on the supply's HP-IB board. The supply contains no batteries.
Output Boards
The output boards are linear dc power supplies. Each isolated output has the L-shaped operating curve described in
Description, page 12 and Figure 1-1.
The ac input to each output board is rectified and applied to a regulator circuit. Each output board employs series
regulation techniques. A regulator element is connected in series with the load and operates in the linear region (between
saturation and cutoff) of the transistor characteristic curve. Regulation is achieved by varying the conduction of the series
element in response to a change in line voltage or circuit load.
The output board receives digital signals from the HP-IB board and converts them to analog signals which program the
output voltage, current, and overvoltage values. The output may be programmed remotely over the HP-IB using
commands (see Chapter 5) or locally from the supply's front panel using the control keys (see Chapter 6).
The output board can be commanded to send measurement and status data back over the HP-IB and/or front panel. The
data is sent back via the supply's HP-IB board. HP-IB readback capabilities include output voltage and current, present
and accumulated status, and all programmed settings. The front panel LCD display can indicate the output voltage and
current, the supply's HP-IB address, error messages, and programmed values. Annunciators on the front panel indicate the
operating status of the selected channel (output board).
Figure 1-2. HP 6621A, 6624A and 6627A Multiple Output System Power Supplies, Block Diagram