Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Deafult 2V on output when setting SVMI mode after power up #186

Open
jmball opened this issue Jun 23, 2021 · 1 comment
Open

Deafult 2V on output when setting SVMI mode after power up #186

jmball opened this issue Jun 23, 2021 · 1 comment

Comments

@jmball
Copy link

jmball commented Jun 23, 2021

I've noticed that when the device (Rev F) is first powered on, setting the channel mode to SVMI puts 2V across the channel output. This means if I want to do a DC measurement using the following:

import pysmu

s = pysmu.Session()
s.devices[0].channels["A"].write([1])
s.devices[0].channels["A"].mode = pysmu.Mode.SVMI
s.run(10)
print(s.read(10))

the device under test gets a blast of 2V when the mode changes to SVMI before the output changes during the measurement. Putting a scope on the output when I run this program shows the 2V stays active for ~18 ms, before changing to the requested 1V.

2V_scope

As far as I can tell, it's necessary to set the channel mode before triggering a measurement so this seems to be unavoidable, which is potentially damaging to some devices. I was expecting the default output on power up to be 0V to prevent the risk of damaging the device under test.

Setting the mode back to SVMI puts the output to the last measured voltage, as expected.

Is there a software solution to guarantee that the default output voltage is 0V when setting SVMI mode after power up? Or is there a way to re-order the commands that I've missed such that the 2V never shows up unless requested?

@jmball
Copy link
Author

jmball commented Jun 25, 2021

It looks like this is happening because the default DAC setting in firmware is 26600 (~2V), https://github.com/analogdevicesinc/m1k-fw/blob/a23df497be7125dd7585d8ad3628cfcaf05cd5ed/src/main.c#L18. Changing it to 0 means that required activation of SVMI mode before the read leaves the output at 0V.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

1 participant