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LMP91000 hookup to Agilent 33220A

Marie Tupaj
Prodigy 140 points
Other Parts Discussed in Thread: LMP91000, MSP430F2274

 

How does the LMP91000 connect to an Agilent 33220A waveform generator?

- Marie

  • 0
    TI__Guru**** 181641 points

    Hi Marie,

    What exactly is it you are trying to do with the Agilent 33220 and the LMP91000?  Are you trying to simulate a sensor of sorts?

  • 0 in reply to Tom Hendrick
    Prodigy 140 points

    Hi Tom,

    I will use the LMP91000 as a three probe electrochemical sensor.  With this sensor, I want to take cyclic voltammetry measurements.  To do this, I would need to send a stimulus (a triangle waveform) to the electrodes through the LMP91000. I will measure the returning current. Would I be able to hook up either a waveform generator to the LMP91000 or use the SPIO-4 board to send a waveform to the electrochemical probes through the LMP91000?

    Thanks,

    Marie

  • 0 in reply to Marie Tupaj
    TI__Genius 9655 points

    Hi Marie,

    the LMP91000 is not a sensor, but a front end for electrochemical sensor (in few words it is programmable potentiostat). The stimulus you want generate should be a current stimulus. A way to make it using a waveform generator like the one you mentioned is the following:

    1. Put a series resitence Rs (in the order of  tens Kohm) between the output of the waveform generator and the WE pin of the LMP91000SDEVAL, conenct the ground of the output connector of the waveform generator to the GND connector of the LMP91000SDEVAL.

    2. Short CE and RE pin of the LMP91000SDEVAL in order to put  A1 op amp in a closed loop configuration.

    3. Program a triangulare wave or any other wave with an offset voltage equal to the Internal Zero voltage you set in the LMP91000, program a right amplitude(App) in the waveform generator in order to not exceed the operating range of the LMP91000.

    best regards,

    Domenico

  • 0 in reply to domenyko
    Prodigy 140 points

    Hi Domenico,

    This solution sounds good. However, will this configuration allow me to input the waveform and also take the resulting response using the SPIO-4 board?  The purpose of this waveform is to send in a potential between WE and RE. The output signal (The response) will be dependent on the electrochemical reaction between the electrode under study and the solution.  We can use this output signal to study properties of the electrode.

    -Marie

  • 0 in reply to Marie Tupaj
    TI__Genius 9655 points

    Hi Marie,

    if you conenct all the baords (LMP91000SDEVAL ->ADC161S626BEB -> SPIO4) you can use the Graphical user interface to configure the LMP91000 and acquire the data.

    The configuration I suggested simply sources/sinks a current in to /from to WE pin of the LMP91000. The bias (voltage between RE and WE) can be configured from the GUI.

    If you want to apply a bias (DC + AC signal) between RE and WE pin this is not possible, but you could use the bias configurability of the LMP91000 to create a DC stairs (positive and negative).

    best regards,

    Domenico Granozio

  • 0 in reply to domenyko
    Mastermind 7675 points

    Hi Domenico,

                        Regarding the LMP91000 i have a few questions:

    I want to use an unbiased sensor with the lmp91000 connected to an msp430f2274. In case of unbiased sensors should I go for internal or external references?

    The Vref is considered 2.5V in the datasheet, you know why (why not 1.5V)?. The Vref range is between 1.5V and Vdd (in my case 3.3V) (page 5 datasheet)

    Regards

    Gastón

  • 0 in reply to Gaston_Melo_Arg
    TI__Guru**** 181641 points

    Hi Again Gaston!

    Since your question about the LM91000 reference is a little different than this original thread topic, I've tried to split it off for you as a new thread.  Seems we're still having a few issues with the updates we've made recently, so I'll split it off as soon as the system allows.

  • 0 in reply to Gaston_Melo_Arg
    TI__Genius 9655 points

    Hi Gaston,

    regarding the reference for unbiased gas sensor you can use also the internal one (which means the supply voltage).

    Regarding  VREF =2.5V in the Datasheet we simply selected that value in order to generate bias voltages which are very common in the gas sensor market.

    As written in the DS the voltage reference can be any value between 1.5V and the supply voltage.

    Best regards,

    Domenico Granozio.