To start this blog, repository of projects, or whatever descriptor is the most apt, I am going to begin with a the one that is recommended to every new electronics student: a power supply. It makes sense, every project afterwards is going to use something similar, the project teaches much about how to select components what do certain words mean in the datasheet. However, I want to approach from a different direction. A functional benchtop power supply that you would see in a lab. However the price range on this kind of equipment is varies widely and capabilities as well.
A no name power supply from Amazon can cost ~$50, but something from Tektronix or Rhode and Shwarz is $3,000. What is the differential that is able to drive that 2 orders of magnitude of cost? Below is the comparison between a no name Amazon supply and a Tektronix, or a Keithley through the virtue of acquisitions.
| Specification | Jesverty SPS-310 | Keithley 2280S-32-6 |
| Voltage Range | 0-30 V | 0-32 V |
| Current Range | 0-10 A | 0-6 A |
| Voltage Accuracy | ± 0.01 V* | ± (0.02% + 3 mV) @ 1mV resolution |
| Current Reporting Accuracy | ± 0.001 A** | ± (0.05% + 5 mA) @ 0.1 mA resolution |
| Load Regulation | N/A | ± (0.01% + 2 mV) |
| Line Regulation | N/A | ± (0.01% + 1 mV) |
| Measurement Rate | N/A | 140 µs |
- * Voltage accuracy is not listed for this power supply other than the resolution of the voltage setting.
- ** Current accuracy is not listed for this power supply other than the resolution of the current setting.
The real value in the Keithley supply is the fact that the specifications are real in the sense that they are guaranteed. The Amazon special doesn’t have these values listed and are pretty bare bones. There isn’t the nice features of remote control and measurement settings. For what I intend to do with this, I do need to measure currents and do data analysis on current draws over time. This would allow for better designs relying on current and voltages that change over time like those found in battery based systems.
For my power supply I want to lean more into the specifications from the Keithley side of design. However, I only need to power from 0 to 24 V and I am limiting my range to 5 A.
| Specification | Buffered Power |
| Voltage Range | 0-28 V |
| Current Range | 0-5 A |
| Voltage Accuracy | ± 5 mV @ 1mV resolution |
| Current Reporting Accuracy | ± 3 mA resolution |
| Load Regulation | ± (0.05% + 2 mV) |
| Line Regulation | ± (0.05% + 1 mV) |
| Measurement Rate | 100 µs |
The next few posts will be about the system level approach to do this. What blocks will be needed to accomplish this and how other power supplies are making there requirements.
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