Help with reading out a load cell (SPICE)

Discussion in 'General Electronics Chat' started by tesnime, May 23, 2015.

  1. tesnime

    Thread Starter New Member

    May 23, 2015
    Hello everybody,
    We are still pupils and are trying to paticipate in a contest.
    it's about reading out a load cell (Please see Data sheet)

    We know that it is too much to ask, but we would appreciate if you could help us especially with the SPICE Simulation!

    1- Output voltage: 0-5v for a load of 0..100Kg.
    2- The whole circuit should be supplied by two 9v batteries.

    PS: the components have to be real (non ideal).

    Part one:

    Our questions are:
    1- how can we minimize the effect of temperature on the output signal?
    2- how can we improve the linearity of the output characteristic?
    3- how can we improve the temperature dependency?

    Part two:
    As we want to evaluate Uout = f(Weight) at various temperature and the static operationg point at a specific load it woul be resonable and beneficia to do a SPICE simulation. The problem is, we have no idea of this tool and are not sure f we could make it at time if we start learning it know.
    So we wanted to ask if any of you could show us an example with the spice tool so we don't invest much time on it because it is just a little part of the project!

    We thank you very much!
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Here's one example of the use of LTspice (a free downlaod from Linear Technology) to model a load cell. It uses a 'behavioral voltage source' B1 to give an output voltage specified by the equation shown, involving cell parameters such as you would get from the cell's datasheet. The plot is the output for loads of 1-5 (assumed Kg, but the units are of your choosing, depending on the maximum cell load).
    mayank rob likes this.
  3. tesnime

    Thread Starter New Member

    May 23, 2015
    Hello Alec t,
    first of all we would like to thank you for your help.
    We were rather thinking about using a full bridge of Strain gaugs, a differential amplifier and a A/D Converter. PLease check he attachement. The problem is we don't know how to dimension our components using the data sheet :/.
    Thank you!