External power supply for Otii Arc

Can someone suggest a external power supply for Otii Arc? It must be 7.5-9V and 5A and have an EU mains plug.

We have seen issues with 5A AC adapters, creating noise in low power measurements.
For 5A supplies, I have used Volgen model KTPS45-0950DT-3P-VI but the measurement will be noisy in uA measurements.
The only low noise supply for 5A we have seen is the Extech 382260.

I can recommend the XP Power VEL18US090-EU-JA that we have used up to roughly 2.7A without problems.

Best regards,

We have ordered and tested with XP Power 9V 4A power adapter and it is much more noisy than using USB or laboratory power supply. Later I found your FAQ page “How do I select the right power supply” and it says that external power adapters with rating above 2A have been found be quite noisy. I wish I knew that.

  • for 0-4.2V and 0-200mA I will use USB
  • for 0-5V and 0-2.5A I will use our laboratory power supply

BTW you datasheet says max current is 250mA, while on the FAQ I read 200 mA, I think you need to update one of them

sorry about the adapter. Working with low power you run into stuff that you otherwise don’t see or care about otherwise. We are collecting recommendations for above-2A power supplies, so please share any experiences, good and bad.
And thanks for spotting the typo, we’ll fix !

Well that’s a bit of luck - I have two of those Extech 382260 supplies at home…

Do you have an input supply noise/ripple etc requirement needed to meet the published Otii spec?

Is the coupling mechanism affecting measurements known?

Hi Jared,

Input ripple for DC plug should be <10mV p-p for noise <1kHz

Best regards,

Cheers Bjorn!
I’ll print a couple of stickers for the back of the Otii’s we have here…

How does the Otii Arc know whether to use the internal or external power supply?

Hi Bruce,

If external power supply is connected and it is within 7-9V then the external power supply is used.

Best regards,

Thanks, that’s what I thought. I am working on an IOT device that has a LORA radio. When the radio transmit, it appears, the arc can not supply current(LORA transmit max ~120mA) fast enough. The voltage drops approximately 300-400mV at the start of the transmission. Is this something users have experienced while using the Otiis? Or do I have another problem?


This is not normal behavior and I suspect the setup.
To dig deeper in this issue, I suggest that you create a case in our case system with information about your setup and attach a Otii project that shows this behavior.

Best regards,