Hi,

The ground for all Artiq channels (ttl, urukul, DAC) is 0.023 V above all our other instruments' grounds. This is causing some problems for us. Curiously, the power supply cable going into Artiq is measuring the same ground as our other instruments. Is there a software solution or is it a hardware issue?

Thanks!

Which TTL card is it? The BNC and SMA cards are isolated and the ground is floating on them.
For Zotino, there is a common-mode choke inserted in each channel, the ground is otherwise the power supply's ground (modulo the input filter on Kasli).
On Urukul, the SMA ground is the power supply ground; it can be optionally floated at DC (and still shunted at AC) by removing 0-ohm resistors.
Does this clarify things and can you elaborate on the problems you are seeing?

Yes it does clarify most of the issue. The 0.023 V difference between BNC and SMA cards grounds and "earth" ground is because those cards are floating as you explained. Ok. There is some floating on the TTL card (SMA ports), but it's much smaller and not an issue.

The main issue we are having is the floating ground on the BNC ports of the zotino channels. We use some of these channels to control high voltage power supplies. The floating ground on the zotino channels causes the output of the high voltage power supply to be unstable if we connect the high voltage output ground to earth ground. If we let the output of the high voltage power supply float, it is stable.

We'd prefer the high voltage ground to be earth ground though as these high voltages are applied to our ion trap's electrodes and the ground of the trap is earth ground.

  • dpn replied to this.

    You have the option to float the Kasli crate using a class II power supply (e.g. with IEC-C7 plug), but you must be fully aware of capacitive mains leakage current through the power supply unit (typically up to 120 V, 100µA AC). It may be harmful to sensitive equipment if the crate is not properly connected to system ground.
    You can use Humfrees Rack Isolation Tabs if you are mounting the Kasli crate in a grounded rack.

    6 days later

    ajras

    The main issue we are having is the floating ground on the BNC ports of the zotino channels.

    Just to avoid confusion, the Zotino BNC outputs are not floating at DC. What you are seeing is more likely a "good old" ground loop between amplifier output, your earth reference ground, and the Kasli mains supply ground.

    As sb10q points out, you might be able to avoid this, i.e., turn Zotino into a floating voltage supply, by using a Class II supply and making sure you don't have any other unintended ground connections. (Running Zotino from a separate DRTIO satellite can be handy to resolve ground loops between different parts of your system.)

      24 days later