Agilent Technologies 90B manual Constant Voltage Power Supply Measurements, Precautions

PERFORMANCE MEASUREMENTS

CONSTANT VOLTAGE POWER SUPPLY MEASUREMENTS

Figure 70 illustrates a setup suitable for the measurement of the six most important operating specifications of a constant voltage power supply: source effect, load effect, PARD, load effect transient recovery time, drift, and temperature coefficient.

The automatic load switch shown in Figure 70 is used to periodically interrupt the load when measuring transient recovery time. Full details of a suitable load switch and the method of employing it are given later under CV Load Effect Transient Recovery Time.

Measurement Instrument	Necessary Characteristics	Suitable Model Number
Oscilloscope	Sensitivity and bandwidth: 100∝ V/cm	Agilent 180C with 1821A time base
	and 400KHz for all measurements except	and 1806A vertical plug-in; 1803A
	noise spike; 5mV sensitivity and 20MHz	plug-in for spike measurement.
	bandwidth for noise spike measurement.
Differential or Digital DC	Resolution -1 millivolt or better at	Agilent 3420B
Voltmeter	voltages up to 1000 volts.	Agilent 3455A
True RMS Voltmeter	Sensitivity 1mV full scale crest factor	Agilent 3400A
	10:1.

Precautions

Measure Performance at Front or Rear Terminals.

Before attaching the load and monitoring devices shown in Figure 70 determine whether the supply is connected for front or rear terminal sensing, because the load and monitoring devices must be connected to the same pair of output terminals to which the feedback amplifier within the power supply is connected. In the case of small laboratory supplies that feature Automatic Error Sensing, performance measurements can be made at either the front or rear output terminals but are normally accomplished at the rear terminals.

Connect Leads to Power Supply Terminals Properly.

Casual clip lead connections will inevitably result in serious measurement errors--in most cases exceeding the power supply's specifications even though the power supply is operating perfectly. The load and monitoring leads must be connected to the power supply terminals exactly as shown in Figures 71A and B. If performance measurements are made at the front terminals (Figure 71A) the load should be plugged into the front of the terminal at (B) while the monitoring device is connected to a small lead or bus wire inserted through the hole in the neck of the binding post at (A). If performance is being measured at the rear barrier strip (Figure 71 B), the measuring instrument should be connected to the plus and minus sensing terminals; in this way the monitoring device sees the same performance as the feedback amplifier within the power supply.

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