Extend voltage capability of EmStat Pico

Hello,

I would like to evaluate an EC sensor with EmStat Pico.

The test method is Cyclic Voltammetry(CV) measurement.

I would like to take +1.5V to -1V voltage swing to WE terminal. And then, the CE terminal voltage will change from -1V(WE=+1.5V) to +0.5V(WE=-1V).

EmStat Pico(and ADuCM355) voltage capability is around 2V. I would like to use EmStat Pico for the sensor.

Do you have any idea to extend the voltage range for the sensor?

If you have any example circuit or applicaiton note..etc, I would like to try it.

Best regards,

Jun

  • Dear Jonnyun,

    I'm afraid that the limits for the compliance voltage, dynamic dc-potential range, and dc-potential range (see table below) are hardware limitations and cannot be extended.

    If you are interested in a higher potential range and compliance voltage, you should have a look at the EmStat3 module (https://www.palmsens.com/product/oem-emstat3-module-2). The successor of the EmStat3, the EmStat4 is already available as a housed version and should in a few months be available as a module as well. You can haver a look at the EmStat4 here:  https://www.palmsens.com/product/emstat4s/

    I'm wondering, what application requires such a broad window for your measurement? 

    Kind regards,
    Lutz Stratmann

  • 0
    •  Analog Employees 
    on Jun 23, 2021 2:01 AM in reply to Lutz@palmsens

    Hi Lutz,

    Thank you so much for your kindly comment.

    I understand that EmStat3 is reasonable solution for my case. 

    I thought that if I can put additional opamp or any external circuit for EmStat Pico,  the excitation voltage might extended.

    In this case, we need to care about internal bias voltages for each front-end. 

    So, I wanted to ask application information for this idea.

    Best regards,

    Jun

  • Hi Jun,

    I would like to clarify that the EmStat Pico does not generally move the WE (vs GND) potential during a measurement, since this could negatively affect the measurement. This means the maximum voltage swing between the RE and WE is 2.6V (in max range mode). However, it is possible to force this by using the "set_pot_range" command between two sections of a measurement. This would, in theory, allow you to use the full 3.7V range of the EmStat Pico between -1.7V and 2V (WE vs RE). I believe you are suggesting you need a WE vs RE voltage of 2.5V which is not possible either way, as Lutz has mentioned.

    It may be possible to extend the voltage ranges in the suggested way, but this would have a number of implications.

    First, this would require you to generate a higher VRail for these external opamps. If you wanted any potential to go below GND, you would also need to give those opamps a -VRail below GND.

    Secondly, it would have a significant effect on the stability of the feedback loop. It may also be necessary to add an additional layer of calibrations, since the opamps will affect accuracy as well.

    Thirdly, you will also need to bias the gain around the WE voltage, this will require an extra opamp as well.

    At this point you would have added quite a lot of stuff on top of the EmStat Pico, so you would need to consider whether that is worth it for your application.

    Kind regards,

    Hielke

  • 0
    •  Analog Employees 
    on Jun 24, 2021 9:10 AM in reply to Hielke@PalmSens

    Hi Hielke,

    Thank you so much for your comment.

    I would like to confirm your comment for my application.

    "Thirdly, you will also need to bias the gain around the WE voltage"

    I think EmStat Pico doesn't have analog input for WE(TIA) input for biasing voltage. It is fixed by internal DAC setting.So, I would like to consider to basing method for WE voltage.

    If I have misunderstanding, please let me know.  

    Thanks again for your kindly support.

    Best regards,

    Jun

  • Hi Jun,

    I am not completely clear on what your question is? I was not talking about the altering the WE voltage in this particular comment.

    If this is something that is being considered for a fairly large number of instruments it would probably be better to contact us directly to determine whether it is feasible. If it is for a small number of instruments I would recommend going for another instrument with a higher voltage range instead.

    Kind regards,
    Hielke