Measurement and control systems for laboratory power supplies
Choose a power supply whose specifications actually mean something!
When you need to buy a general purpose dc power supply, there are a bewildering number of manufacturers to choose from.
When you read the specifications they all look much the same. Most quote load regulation figures of around 0.01%. Some quote a volt meter accuracy better than your DMM.
In practise, however, these figures are almost meaningless because they omit the essential feature needed to achieve high accuracy and good load regulation - remote sensing.
Even the best known names in the business omit remote sense from their lower cost power supplies - so does it really matter ?
Remote Sense - do you really need it ?Well it depends upon your application. If you're working at very low currents then probably not.
If you don't need to know the voltage at the load accurately, then possibly not.
What may not be obvious is how poorly regulated and inaccurate a power supply without remote sense can become.
A two metre length of a 24/0.2 wire pair has a resistance of around 0.1 Ohms. For a 5V load drawing 3A the metering error without remote sense would be 0.3V with an effective full current load regulation of 6%.
It makes a nonsense of specifications such as 0.01%.
Even the more basic TTi power supplies, such as the EL-R and EX-R series shown above, have remote sense capability. You can choose local or remote sense at the flick of a switch - so if you don't need it, you don't use it.