CEL lab tour: power supplies

A bench power supply is at the heart of every electronics workstation. A modern switched-mode supply is compact and efficient – so why does CEL use these older units that are big, heavy, and which keep the lab warm in winter?

The HP / Agilent 663xB series is a linear design, which means the output is ultra clean with no switching noise that can interfere with the connected equipment.

One of CEL’s specialist areas of expertise is in ultrasonics, where the signals received from transducers are very small, and the precision with which they can be measured determines the accuracy of the finished product. Having a source of power which is free of RF noise is essential when developing these sensitive circuits – even if the finished product won’t have this luxury.

The 663xB series is also able to sink current as well as source it, which means it can be used to simulate a rechargeable battery. With mutiple PSUs, one can substitute for the project’s battery (in any chosen state of charge) while others supply the charging current and whatever voltage rails the project requires for its own use. Each PSU also includes accurate current and voltage meters, removing the need for separate multimeters and ensuring no unexpected conditions go unnoticed.

Recent projects for which the particular capabilities of the 663xB were useful have included:

– functional testing of power supplies which were customer returns, to determine whether or not they were genuinely defective, and if so, the root cause of the failure and the possible consequences for the equipment they were powering

– developing an automotive project which contained its own Li-ion backup battery, designed to maintain power to the equipment when disconnected from the vehicle supply

– determining the true resistance of automotive power cables, which were suspected of not meeting their published specifications for conductivity and copper content

CEL has all three models in the 663xB series: the 6632B (20V/5A), 6633B (50V/2A) and 6634B (100V/1A), so all requirements from low voltage logic up to 24V automotive supplies and beyond are covered.