Question: I have an analog motor controller that has a B10K potentiometer on it. I'd like to be able to swap out the analog potentiometer for a digital one, but I'm not exactly sure what voltage is being sent to the original potentiometer as I don't have the spec sheets for it.

My current specifications, which work as a prototype, are:

```
- Power supply: 48V 4A transformer, connected to...
- Variable speed DC PWM Motor Controller which controls...
- A 130V 1A max DC motor. 

```

I'm fine with the power and speed that 48V gives me, but do I need to specifically look for a digital potentiometer that can handle high voltages, or would a standard 10K digital pot work?

Answer: 
When designing a transmitter with the XTR115/6 your options are limited by the chip specifications. In particular the 5 volt regulator output current is limited to < 12 mA. There is a knee in the voltage output at 1 mA of current where it drops to about 4.5 volts where it remains up to Imax.

You will find that if you are designing industrial 4-20mA devices, this is about the maximum power budget you have available since the loop specifications are made to limit power for intrinsically safe environments.

Note that if instead of using the internal regulator, you add a buck converter to your circuit, for example, you are adding "energy storage" devices to the design which will force you to go through certification if you desire an IS rating. If you already have other "non-simple" devices in your design, this may not be a deciding issue.

Edit:

You may find [this](http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slyt488) app note from TI regarding harvesting energy from a 4-20 mA loop applicable to your situation. They walk through a design using a TPS62125 to provide a 10 mA supply with some higher peak current capabilities.
You have a few options but it depends on how much current you require and how much burden voltage you can tolerate.

The obvious solution is to use a small DC-DC converter to step the incoming voltage down to a lower value. This will give you more current at the expense of increasing the minimum burden voltage.

Please modify your question stating exactly what your requirements are.