Power supplies provide steady, precisely controlled electrical energy to electronic equipment.
One type of supply, the uninterruptible power supply, powers electronics in the event of an emergency by keeping a battery constantly charged. When the main power goes out, the battery takes over before the equipment can power down.
Uninterruptible power supplies are rather uncommon in most labs, except for standalone computer equipment that might suffer from data loss. Academic and industrial research organizations usually have house backup generators for heavy equipment and instrumentation, and backups for both computer power and data.
Most common lab instruments have their own integrated power supplies, which enable users to plug them into a common electrical wall outlet. The power supply first uses a rectifier to convert house alternating current (AC) into direct current (DC), the only type that common instruments and devices use. It then adjusts the current and/or voltage upward or downward to meet the needs of the instrument. Throughout the device’s circuitry, additional power circuits step up or step down the current according to the various subcircuits’ needs.
One way to differentiate power supplies is to look at how they operate. Switching power supplies use a switching generator to harness efficiencies when converting electrical energy from the grid’s AC to specific DC current and voltage requirements. Switching supplies work by rapidly turning on and off. Linear power supplies operate at constant, precisely controlled voltages.
Switching power supplies are common as embedded supplies for personal computers because of their high efficiency and small footprint, but they tend to be electrically noisy and don’t regulate as well as linear power supplies, says David Pereles, marketing segment manager at Tektronix (Beaverton, OR).
Stand-alone power supplies, including uninterruptible supplies, do make sense in non-electronics labs when a lot of equipment runs on the same voltage, says Mark Swift, business development manager at Universal Electric (Canonsburg, PA). “It’s easier to provide the right electrical energy from a single piece of gear.” Other benefits are ease of connectivity and protection against heat or loss of power.
Physics and chemistry labs, particularly R&D and academic labs, use power supplies to drive basic equipment or to supply direct current in much the same way as a battery.
Electrical/electronics lab power supplies come in three major types, depending on the work being done. Constant voltage supplies provide configurable DC voltage that is adjustable over a specific range that includes zero voltage. Constant current supplies output-regulated current independent of the voltage. Constant voltage/ constant current devices provide either voltage or current.
Varying voltage or current is common when prototyping an electrical circuit to do a particular task, such as timing, counting, or signal processing. “Certain circuits rely on variable voltage thresholds,” Mr. Pereles says. “Changing the voltage is useful when performing a comparison of how the circuit operates at different voltages, or in supplying accurate reference voltages or currents.”
Mr. Pereles says that when choosing the right power supply, the first consideration is what voltage and current are needed followed by how many outputs are required.
Model 1693, 1694, 1900, 1901, and 1902 DC Power Supplies
- Switch mode power supplies provide current up to 60 amps and power up to 960 watts
- Feature a complement of diverse features
- Lightweight and compact
- Provide high power and high current performance at low cost per watt affordability
B & K Precision
A Series DC to HVDC Converters
- Occupies less than one-tenth of a cubic inch of volume; ¼ of an inch thick
- Controllable output voltages range from 100 volts to 6,000 volts
- Features a low-noise quasi-sinewave oscillator
- Input/Output Leakage Current, <100nA
EMCO High Voltage
ESC Series Electrostatic Chuck Modules
- Features clean, accurate and easily controllable voltages required for semiconductor based electrostatic chuck wafer applications
- Precisely secure wafers during lengthy process cycles
- Versions are available with a ground referenced reversible output, in addition to units featuring a true floating bipolar output with associated floating center tap point
Spellman High Voltage Electronics
Starline Plug-in Raceway
- Available in 20, 40 or 60 amps bussing; 120V or 240V; 5 wire
- Customizable lengths of raceway sections up to 10ft
- Optional Isolated Ground
- Various Plug-In Modules are available complete with breaker and receptacle, and can be relocated anywhere on the raceway quickly and easily