Hello,
Would you please provide me more information about measurement for device with >5v voltage? For example, 12v device.
Thanks
Hello
Otii is only designed for up to 5V. However, we do have customers with the same request.
One solution is to simply insert an isolated DC adapter or power supply in line with the Otii main terminal.
This would boost the voltage range, and you would get full benefit of the current measurement’s dynamic range.
You would not get the correct voltage and energy readings, as the Otii only sees its local voltage, but current measurements would be correct.
The limitations are the needed voltage ranges, please supply more details if you want to proceed with this solution.
If we assume four Alkaline batteries in series, running from 1.6V down to 0.9V each, in total 6.4V down to 3.6V, I then recommend using a 3V adapter, giving good performance for this voltage range.
It is important to use good quality DC adapter or power supply to avoid noise and regulation issues, and depending on needed current you might need an adapter to power the Otii as well.
This setup have been verified and is being used.
Hope it helps!
Hi, just going to hijack this thread because i have more questions. So if my intended voltage range is 0-7.2V, should i use a 7.2V power supply and then feed the otii through? and in this situation are we leaving the main power on the otii off and just reading the main current?
Thanks
If you leave main power off on the Otii Arc you won’t be able to measure any current as the output relay is open.
The Main terminals has to output at least 0.5V. The maximum voltage output with only USB power in high accuracy mode will be 3.75V so to get a control range of 3.95 to 7.2V you would hook up a floating 3.45V power supply in series with the positive main terminal (remember the negative main terminal is grounded). By turning the main output off the voltage would be 0V as the output relay will physically interrupt the connection.
Right I’ve got you. Thanks for the info, ill give this a go.
Late to the party but…
We’ve bought the OTII over a year ago due to a recommendation of another company but rarely using it mainly due to the reason that there is no official support for higher voltages that 4.55V (took us some time to even figure out that you require a dedicated power supply for higher voltages).
I’d be great if there is a offical documentation page for using the OTII with the described hack. Otherwise, another working day of one of our engineers will be tied just finding out something that should work out of the box. In general, the documentation on this device is a bit thin. I think Qoitech is working on it but it’s still poor.
Other things that still won’t work:
- If otii is open, our windows workstations cannot hibernated/sleep which led to our workstations unnessesarily running for days
- Using a shunt resistor never really worked will to measure micro amperes of voltage, way to much noise. Why is there no built in solution for that?
Hi and welcome to the forum!
Thank you for your feedback
We are continuously updating help section and if it is unclear then we are happy to improve.
The limitations are shown in the Tech Spec but also in the chapters regarding how to connect your device.
Let me know if it needs to be more clear or if the Tech Spec is hard to find, please.
Regarding connecting Otii Arc in series with an isolated, maximum 5V power supply, is a hack that makes it possible to increase the voltage. This is not something that will be described in the official documentation as this hack makes the voltage and energy calculations wrong.
Feel free to use it anyway.
Regarding your notes about things that doesn’t work.
When Otii is opened and a recording is ongoing, then Otii prevents the computer to go to sleep and hibernation due to that this will stop the recording. We do not want this to happen by mistake, that’s why we have chosen this.
I am interested to hear more about your problems with using an external shunt resistor, what is the level of noise that you see and what size of shunt resistor are you using?
Make sure that you have short twisted cables to not pick up a lot of external noise.
The built in solution for switching shunt resistors is implemented in the main channel, not the ADC channel.
I am happy to help you achieving as low noise as possible using the ADC channel.
You can contact me at support@qoitech.com for a deeper discussion.
Best regards,
Björn