0 Practical you need to tips know about your power products Simple ways to improve your operation and measurement capabilities
Use Remote Sensing to Compensate for Load-Lead Effects Tip 1 I3 When your power supply leaves the factory, its regulation sense terminals are usually connected to the output terminals. This limits the supply’s voltage regulation abilities, even with very short leads. The longer the leads and the higher the wire gauge, the worse the regulation gets (Figure 1). Compare the output impedance of a well-regulated 10 A supply, which might have an output impedance of 0.
Charge and Discharge Batteries in Less Time Tip 2 Using a power supply in constantcurrent mode (Figure 1) is a simple way to recharge batteries, and it also lets you achieve 100% charge levels. On the downside, this method is slow, taking as long as 14-16 hours because the charging current is only a fraction of the battery’s amp/hour rating. Pulse charging, also called transient mode, shortens the charging time, yet still charges the battery to over 90% capacity (Figure 2).
Tip 3 Increase Safety with Remote Disable Feature Remote disable offers a safe way to shut down a power supply to respond to some particular operating condition or to protect system operators (in response to a cabinet door being opened unexpectedly or someone pushing a panic button, for instance). Remote inhibit (RI) is an input to the power supply that disables the output when the RI terminal is pulled low (Figure 1). Shorting the normally open switch turns off the supply’s output.
Tip 4 Eliminate Noise from Low-Level Measurements Noise in low-level measurements can come from a number of different sources, and it’s easier to eliminate noise than to filter it. Check these noise sources: 1. Power Supply Starting with a low-noise supply is naturally a great way to keep noise out of your measurements. Linear power supplies have lower commonmode noise currents, and generally operate at low frequency.
Tip 5 Use Down Programming to Increase Test Speed Under light or no load conditions, a power supply’s output capacitor discharges slowly. If you’re using the supply as a static voltage source, this is not problematic, but when you’re making tests at varying voltage levels, slow discharge means slow tests. Down programming circuits in power supplies rapidly decrease the output voltage, reducing discharge times by hundreds of milliseconds.
Ensure Proper Power-up with Foldback Supplies Tip 6 Foldback power supplies protect connected equipment by reducing excess current (and thus output voltage) along a foldback path. When testing foldback power supplies using an electronic load, you need to take steps to be sure the power supply starts properly.
Tip 7 Connect Power Supplies in Series or Parallel for Higher Output Connecting two or more power supplies in series (Figure 1) provides higher voltages, but observe these precautions: Connecting two or more power supplies in parallel (Figure 2) provides higher currents, but again, observe these precautions: • Never exceed the floating voltage rating of any of the supplies. • Never subject any of the power supplies to negative voltages.
Tip 8 Use Your Power Supply to Measure Pulsed Current As a simpler and cheaper alternative, use a power supply with built-in measurement capabilities. The Agilent 66312A and 66332A dynamic measurement dc sources store up to 4,096 data points at sample intervals from 15.6 ms to 31,200 s. Like an oscilloscope, they acquire pre- and postYou could use an oscilloscope to mon- trigger buffer data by crossing a user-set threshold.
Tip 9 Characterize Inrush Current with an AC Power Source/Analyzer The inrush current characteristics of ac-dc switch mode power supplies vary with the turn-on phase of the voltage cycle. Usually, these power supplies have input capacitors that draw high peaks of inrush current as they charge from the rectified ac line at turn-on.
Tip 10 Use a Power Supply to Measure DUT Supply Current Accurately measuring DUT supply currents above 10 A is beyond the range of the typical DMM in ammeter mode. You could use an external shunt and the DMM’s voltage mode, but using the power supply itself is a better solution. Many supplies include an accurate measurement system, including a shunt. Using the power source’s shunt to take current or voltage measurements at the DUT can be as simple as sending a MEAS command.
Power products that do more and less demand Agilent Technologies’ “one-box” philosophy means we pack more and more capability into the power products themselves, in some cases giving you a rack’s worth of capability in a single box. By offering more, these products demand less from you—fewer instruments, less rack space, simpler test setups, and lower cost of ownership.
Power you can count on year after year We’ve been a leader in the power products business for more than three decades because engineers like you know they can count on Agilent performance, reliability and value. Even our least-expensive dc supplies offer low ripple and noise with tight load and line regulation. Our highprecision products give you the exact power levels you need, with accurate readback measurements to match. Plus, every product you see here is covered by a three-year warranty.
Power products that do more and demand less Multiple-output dc supplies Modular power system Electronic Loads The Agilent 6620-series’ multiple outputs and integrated I & V readback dramatically simplify the job of system integration and maintenance. Plus, the 6625A, 6626A, 6628A and 6629A models offer the precision of 14-bit dual range programming and readback. With rack space at a premium, the Agilent 66000 modular power system’s growing popularity is no surprise.
AC power source/analyzers From avionics to uninterruptible power supplies, customers are demanding products that can use power efficiently while handling all kinds of ac line disturbances. To make sure your products meet these growing expectations, test them with the Agilent 6800-series ac power source/analyzers.
You’re trying to get the most from your power products and get the best power products for your money—-and this booklet is a great place to start. You’ll find 10 easy and practical ways to improve power generation and measurement, along with a brief look at our most popular power instruments and systems. For more information, please use the reply card inside, visit our website at www.agilent.com/find/power, or call Agilent at 800-452-4844.
