Best Practices#

At Qblox, we recommend specific best practices to ensure both the longevity and optimal performance of the SPI rack system. These practices aim to minimize noise and prevent ground loops within your setup. Given the SPI’s numerous separate components, it’s crucial to allocate sufficient time for its initial setup and adhere to the guidelines outlined in the setup pages.

Once your system is set up correctly, the actual use of the system is quite straightforward, you can check out the tutorial. Below you will find extra tips to make sure your experiments work as smoothly as possible with the SPI system.

Hardware#

  • If you switch off the mains or the power supply unit (PSU) while keeping the SPI rack on, the battery will take over the role of supplying power to the rack. If you keep this configuration for a long time, this will slowly drain out the batteries. Therefore we advise you to use the battery powered mode only when there is a shortage of mains supply. If you are not using the rack, please keep the SPI rack turned OFF.

  • The battery is strongly advised to always be used in the SPI setup together with the PSU and the SPI rack. With the PSU being turned ON and the SPI rack switch turned ON in the advised order above, the batteries will be continuously charged in the SPI setup.

  • If you have a spare battery, it is strongly advised to charge the battery within the SPI setup (PSU - Gyrator - Battery, excluding connection to the rack) to extend the battery pack’s shelf time. This can be done monthly: and keep the battery charging overnight up to 24 hours to ensure that the battery is fully charged.

  • Please do not add or remove modules while the SPI setup is powered on.

  • If two modules have the same address, they will be considered equivalent by the C1B and therefore any commands to this common address will be sent to both modules. Remember module address!= slot number! Addresses are hardcoded inside the modules themselves and cannot be changed by software.

  • DACs are numbered starting from 0 on software but starting from 1 on the hardware.

  • The C1B and the C2 have two matching pairs of LEDs that indicates to users when the two modules are sending and receiving commands. Those LED lights should be OFF and only blinking if the box is communication with the PC. If either or both of the LED lights are constantly lit (yellow), this means a problem in establishing communication. Please change the USB port until both lights are OFF.

  • The gyrator has two LEDs on its side to indicate correct operating conditions, as seen in the red box indicated in the figure below. Green LEDs correspond to an “OKAY” status. If one or more LEDs are OFF then this signals an issue with the PSU or gyrator. In this case please turn down all the output current and voltages, turn OFF the rack and report the problem to the customer support team.

../../../_images/Gyrator_LEDs.jpeg

  • Each S4g DAC has a voltage monitor, this is the voltage that is on the output which you can measure it independently without affecting the output current. It can be useful to determine the load impedance (since you know the output current and voltage, you can calculate the impedance). Or to know the headroom before the output starts clipping (if the voltage gets too high, the output will be limited and the set current won’t flow).

  • Each S4g DAC has an LED, the LED will turn on to notify the user when you are hitting voltage compliance.

Software#

  • Please always use the SpiRack driver from qblox_instruments package, namely always dofrom qblox_instruments import SpiRack. Avoid usingfrom spirack import SPI_rack because this can lead to unexpected behaviors in physical outputs when changing spans of D5a/S4g. By all means, avoid changing your spans when connected to an actual experiment.

  • For a quick sanity check to ensure proper connection to the SPI rack, query spi.temperature() and spi.battery_voltages() when starting your experiment. Make sure that the power supply switch is on and the SPI switch is on.

  • spi.battery_voltages() will return a tuple, keep an eye on the positive voltage as you initialize your notebook, positive should be greater than +6V and negative, less than -6V. If the positive voltage is dropping then we suggest charging the battery with the gyrator and PSU overnight with no connection to the SPI. If the issue persists please contact the customer support team.

  • Ramping is your best friend, keep ramping_enabled==True (False by default) for your DAC and you will always ramp your current and your voltage and you will avoid voltage/current spikes.

  • spi.set_dacs_zero() will safely ramp all DACs of your system to zero.

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