Because they utilise an efficient switch mode topolgy AP series units are compact and relatively lightweight for their considerable power outputs. They are suitable for stand-alone bench use or for integrating into systems.
The voltage and current capability of the units can be determined when in use from two front panel bar graphs which show volts with available current, and current with available volts.
Output can be constant voltage or constant current and the mode in use is shown by LED status indicators (flags) on the front panel. Twin digital LED panel meters are provided to monitor both voltage and current. Output is adjustable from near zero to maximum volts and from near zero to maximum current by 10-turn front panel controls.
Alternatively, the output can be controlled from the rear panel using a variable voltage or resistance, or can be remotely programmed by a computer on the GPIB if option /H is fitted.
An OUTPUT ENABLE button is provided on the front panel. When not pressed in, the panel meters and bargraphs display the prospective output settings.
This is done without having to open circuit the load to set the voltage, or short circuit the output to set the current. When the OUTPUT ENABLE button is pressed in, the meters and bargraphs display the actual voltage and current being delivered to the load.
CV/CI power supplies are inherently safe as both output voltage and current will be automatically limited to the preset values. However, to enable the user to protect the load from an inadvertent application of an excessive voltage, the units incorporate an overvoltage limit (OVL) which causes the supply to down program when the preset level is exceeded. It can be adjusted by rotating the adjust OVL control through the front panel. The OVL level can be monitored on the voltmeter by depressing the display OVL button.
When the OUTPUT ENABLE button is not pressed in, the trip level can be accurately set without activating shutdown or disconnecting the load. A tripped OVL can be reset manually or via a GPIB shutdown/enable command. When used with option/H the OVL may be set remotely overriding the local setting. If the power supply overheats, due to restricted airflow for example, the output shuts down automatically and the overtemperature flag OT in the status window lights up. When the unit has cooled sufficiently, the output returns and the flag turns off. Both OVL and OT conditions can be reset using the OUTPUT ENABLE switch.
Protection is also provided against severe reductions in AC power line input (brownout) which could cause overheating or unreliable operation. The output will shut down until the AC power line returns within operating tolerances. An undervoltage condition can be recognised by UNREG and ENABLED lamps being illuminated, together with near zero readings on the panel meters. Should the terminal cover be removed whilst the unit is operating a microswitch inhibits the output circuitry and the panel meters indicate zero.
When supplying a load which is some distance from the output, the remote sensing terminals should be used to maintain regulation at the load rather than at the units output terminals. Up to 0.5 volts drop per load lead can be allowed for without degrading the specified CV performance.
Up to four units can be connected for auto-parallel (master/slave) operation to increase total output current. Control can be maintained from one master unit whether the units are used under local or GPIB control (option /H needed for GPIB). Several units can be connected for auto-series (master/slave) operation, the floating voltage limitation being 120V DC maximum between output and ground. Positive or negative tracking outputs can be achieved by grounding the centre of the series combination, or at any unit in the chain if an unbalanced positive and negative supply is required. Neither rail should exceed 120V DC with respect to the ground.
A current monitor output signal of 0 to 5 volts for zero to full current is provided. This is useful for the remote display of output current. It also provides the capability for auto parallelling power supplies should this be a requirement.
A GPIB interface card is available as a factory fitted option (/H). When fitted this allows high resolution (up to 1:4000) control and readback of output. The option also activates LEDs which indicate if the power supply is talking or listening or whether a service request signal has been sent.