Setting SMU to 0 V after measurement

General
1

Hi there,

I’m using SweepMe! to automatize a gas-sensing setup. The general ideia is keeping MFC-N2 at a constant value, vary the flow of MFC-Sat, to achieve different concentrations of the gas flowing through MFC-Sat

I’m having a hard time setting a SMU voltage to zero after the measurement. The SMU should perform a single-point voltage measurement. After that, a new flow is set in the MFC-Sat. The time to reach a new concentration in the chamber is calculated is passes as a hold time. After that time, the SMU should perform the single-point measurement again.

However, after the first loop, the SMU keeps applying the current while treach is achieved.

Is there a way of setting the Current or voltage to zero once the measurement is done?

2026-10-02T17-20-34_Sequencer
2026-10-02T17-20-34_Sequencer603×716 11.4 KB

Thanks!
Jonas

1 Like
2

Hi Jonas,

thanks for asking your question. It is surely one of the situation where we need to dive deeper in how the sequencer works.

Right now, you have created two branches:

  1. From MakeFile to Delay
  2. From MakeFile to SMU

In your first branch, there is probably no sweep as all modules have a single sweep value or no sweep at all. The Delay module is I guess used to wait 5 seconds to settle after the value of MFC-N2 is set. If this is the motivation, I suggest to use a Hold module instead of a Delay module. Hold directly waits after the apply phase and before the measure phase.

Delay can be used to make measurement points equidistant in time, e.g. if you want to measure a sensor over time every second. Delay then makes sure that the next point starts exactly 1s after the previous measurement point started, independent from how much it took for the communication inbetween (that can vary).

Once your first branch is done, all modules in the first branch that are not in the next branch are unconfigured. This is only Delay in your case. Delay does not really unconfigure because there is nothing to unconfigure for a Delay module.

The modules MakeFile, K_solvent, Molar_mass and MFC-N2 are not unconfigured because present also in the second branch where they are still active and do their job at every repetition that is created by a sweep.

Now, in the second branch, treach, MFC-Sat, Calc ppm, Hold, SMU are configured. However, as long as MFC-Sat is performing its sweep, the second branch stays active and all modules stay configured. And this also means that the SMU module stays active all the time and applies its value.

So how can you switch off the module SMU. A dirty trick would be to use two sweep values for SMU: the voltage you need to know and 0 V to switch it off. Then, the SMU module would always make two measurement for each MFC-Sat value, but it would also apply the hold time for each of this two values.

The cleaner solution would be two create a third branch, by putting the SMU module underneath Hold but not nested into it. It would be then nested into Calc ppm. This way you first hold the time to reach the setpoint of the MFC-Sat, once this is done, you change into the third branch, where the SMU is configured, applies the value, makes the measurement, and unconfigures, because the sweep in the third branch is done and it goes ahead with the next higher sweep that is done by MFC-Sat and you are back in the second branch.

So, a long explanation for a small change. :slight_smile:

Likely, you will have a lot of measurement files because, MakeFile creates a new file for each branch. You can modify this behavior by putting MakeFile nested into treach and MFC-Sat into MakeFile. Then, you only get files for the second and third branch.
Furthermore, you can modify the properties of MakeFile by double-clicking it. You can configure whether you like to add a branch index or repetition index. Normally, these indices shall ensure that no file has the same name again. But in your case, you want to write all data into one file for the third branch to later evaluate voltage vs MFC-Sat flow rate.

If you still have problems with running the measurement, you can also select all modules and use copy. Then paste it into a code box in the forum.

The modules and how they are arranged can be sometimes a bit complex when it comes to not trivial measurement like “every voltage for each temperature”, but this concept helps us to cover a lot of different measurements with a few clicks once one is used to the scheme.

For further understanding, I can recommend to have a look a the function calls of the sequencer procedure:
https://wiki.sweep-me.net/wiki/Sequencer_procedure

We have also trained a custom GPT to help with setting building
https://chatgpt.com/g/g-67f7ab5cef588191b5680545d25e82b9-sweepme-setting-builder

Not always perfect, but gets better the better AI gets.

In SweepMe! 1.6 that is now out as beta and will be released as live version next week, we have included an MCP server. This allows AIs like ChatGPT Codex or Claude Code to directly interact with the sequencer, by reading sequencer, modifying them, adding them and running SweepMe! to create agentic workflows. However, SweepMe! 1.6 requires a SweepMe! Pro license to run multiple branches.

Let us know if you are able to resolve the issue or if you need further help.

Best, Axel