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Original question:

LMP91000EVM: sensor interfacing

LMP91000EVM: sensor interfacing

sankar itraju
Prodigy 20 points
Part Number: LMP91000EVM
Other Parts Discussed in Thread: LMP91000,

HI sir 

here am attaching my experiment pics please check it once 

am trying to get values from screen printed electrode but am unable to get output from LMP91000 board along with SPIO-4 

please someone help me out. If am using PS trace software from palm it is given values with their device(not lmp91000 board) he is using" Differential Pulse voltammetry" method 

am using LMP91000 Software tool but I  did not get values .

my electrode is https://www.palmsens.com/product/italsens-is-c/ 

still I do not know what are the settings should I make on LMP91000 and SPIO-4 boards as well software side lmp91000 tool

  • 0
    TI__Expert 8880 points

    Sankar,

    Most likely you do not have the EVM configured correctly for your probe. The sensor manufactures have basic settings for their sensors. However these basic settings don't always apply to every design or IC that can be used to measure the sensor. The LMP91000 is a transimpedance amplifier that is very sensitive and low current. Small adjustment to gain and Rload will have big impact to your readings.

    Most designers, begin with the incorrect settings for the LMP91000 board. In the GUI Software find a sensor that is similar or the same as you are using and change to these default values to begin. Only if you are using a standard solution with the sensor can you know exactly what value you should be getting. Adjust the settings until you get the correct voltage feedback for the standard you are using. 

    Try adjusting gain and Rload after you configure the GUI for your probe. This should get you a good reading. You will have to craft a formula to get the real values from the voltages you will be measuring. Use the standards to get known voltage for know standards then you will be able to create the formula. Don't forget to temperature compensate the voltage to get more accurate measurements. 

  • 0
    Prodigy 20 points

    Hi sir thank you for quick replay , I did not find suitable sensor in LMP91000 software database .

    when I asked to supplier who are supplying sensor (italsens-is-c ) he said that we do not have any sensor parameters, The parameters completely depends on electrochemical experiment..    

  • 0 in reply to sankar itraju
    TI__Expert 8880 points

    Sankar,

      Can you supply the part number for your sensor? Include manufacture.

    What are you attempting to sense? 

    I will see what I can find out. It's not good when a sensor manufacture can't help you with settings.

    What is the current from min to max measurements?

  • 0 in reply to Gordon Varney
    Prodigy 20 points

    Hi sir Thank you so much for helping me here am giving sensor type 

    my electrode is https://www.palmsens.com/product/italsens-is-c/  from palmsens 

    The main intension to buy the TI boards LMP91000 and SPIO-4 is to measure current from screen printing electrode(SPE)

    I do not know how much current should I apply to SPE what is the procedure to measure current from SPE with LMP91000EVM 

    I also bought MSP430 microcontroller board but i do not know how to interfacing it with LMP91000EVM.

    The minimum current from SPE is 10nA and max 2mA 

    I do not know what are the settings should I make on LMP91000 board along with SPIO-4 here am using LMP91000 software tool 

    Sir please help me am struggling since so far my experiment structed up ...

    thank you Sir am waiting for your reply ....  

  • 0 in reply to sankar itraju
    TI__Expert 8880 points

    Sankar,

      It's very difficult to setup the LMP91000 when the sensor specifications are unknown. Let's start with, what are you trying to measure?

  • 0 in reply to Gordon Varney
    TI__Expert 8880 points

    Sankar,

     The information you are looking for is in the sensor data sheet. Please take some time to read the data sheet entirely. This is a 3 pin sensor with a potential of up to +/-20uA. The image is from the data sheet.

    Start with a fluorine E23E1 setting from the select a sensor option in the GUI. Then adjust the gain and Rload as needed to get the results you are looking for.

    The in out for the LMP91000EVM is in the documentation on TI.com. The same is true for the MSP430 Launchpad that you have. You need an ADC input and an I2C interface. Make sure you use pullup resistors for the I2C bus. Read, read read, its all there for you.