When choosing programmable AC sources and DC supplies, look beyond the headline specs, such as power and voltage, before purchasing. Choose a vendor who offers flexibility concerning interface options, software support, size and weight, output measurement capabilities, and environmental conditions.
- Make sure you have flexible control and interface options.
You’ll find that manufacturers offer a variety of interface options, ranging from front-panel control to Ethernet connectivity. Front-panel control can prove helpful in test setup and simple tests. Look for a front panel control that provides precise fine-tuning and lets you quickly sweep the output over a wide range. AMETEK Programmable Power uses a dynamic rate-change algorithm to provide this functionality.
To facilitate centralized control of multiple instruments, consider Ethernet or USB. Other interface options include analog, RS-232C, and GPIB. These venerable interfaces are becoming less popular but may be useful if you integrate a new instrument into a legacy system. Knowing what’s available will allow you to select the control and interface options that best suit your needs.
- Consider the software environment.
You will need software if you are using a computer to provide remote control of your source or supply. You can use a GUI to control your instrument’s output parameters for simple applications. AMETEK Programmable Power, for example, offers its Virtual Panels GUI, which supports multiple sequences and steps, including programmable ramp-up and dwell times and programmable on-off delays. Also, look for a vendor who provides software support for specific industry verticals. For the aerospace industry, for example, AMETEK Programmable Power offers Virtual Panels avionics options that let its programmable AC and AC + DC sources simulate power-output conditions specified in relevant aviation standards.
If you are using one or more AC sources or DC supplies in a system that also includes other instruments, you will want to write a custom program in a language like Python to generate the SCPI commands to be sent to your instruments. Make sure to choose a vendor who is agnostic concerning the high-level languages you choose.
You will also need a driver for each power supply or instrument you plan to control remotely. Ensure instrument vendors can provide drivers compatible with your host computer’s operating system.
- When choosing an AC source or DC supply, look for minimum size and weight.
As manufacturers incorporate more innovative components into their programmable supplies and sources, they can increase power densities and decrease the rack or bench space necessary for a given power rating. For example, AMETEK Programmable Power’s new Asterion DC ASM Series supply packs 1,700 W into a 1U-high rack width. A legacy supply with the same power rating would have consumed a full 3U-high rack width.
In addition, look for an AC source or DC supply with forced-air cooling provided by a variable-speed fan that draws air in from the front and sides of the instrument and exhausts it out the back. Such a source or supply will save you space by not requiring additional vertical clearance when rack-mounted with other instruments. Finally, look for low acoustic noise levels. The ASM limits acoustic noise to 68 dBA measured at 1 m.
- Choose a source or supply that provides flexible, accurate output measurement capabilities.
A source or supply that measures output parameters can eliminate the need for separate instruments such as DMMs. Supplies and sources can display the measured values on their front panels or convey them over a digital interface to a remote host computer. A basic DC supply will measure output voltage and current, but you may also want other useful features. For example, the ASM can present a reading that averages up to five voltage and current samples to minimize noise. It also allows you to set voltage and current limits. An AC source should measure output voltage and current as well as several other parameters. The Asterion AC, for example, includes DSP-based measurement capabilities that enable it to measure fundamental frequency, harmonic frequencies (to 48 kHz), phase, real power, apparent power, and power factor.
- Determine the operating environment.
Typical sources and supplies operate over a 0 to 40°C temperature range, at an altitude to 2,000 m, and with humidity from 5 to 95% (non-condensing). That’s more than adequate for the average lab or production facility. However, if you will be using your instruments in an environmental chamber that varies temperature, pressure, or humidity outside of these limits, talk to your vendor about any need for derating or other steps.
Carefully consider the options and tradeoffs in all five categories presented here to ensure you choose AC sources or DC supplies that address your project requirements and avoid costly replacements.