Custom Pressure Transducer Amplifier Box

Discussion in 'General Electronics Chat' started by manuu84, Jun 16, 2009.

  1. manuu84

    Thread Starter New Member

    Jun 16, 2009

    I am a biomedical engineering grad student. In our lab we are using edwards pressure transducers (TruWave) for various purposes. Since we are a couple of students sharing only one box I looked into making one myself.

    I have taken my last circuit class a couple of years ago, so be patient with me :).

    This morning I have read through old threads and postings regarding this topic and got some information out of it. However, it did not really give me a definite solution.

    What I think I need:

    - A voltage source for the semiconductor wheatstone bridge (Voltage unknown, I am assuming it will be between 5 and 10 volts)
    - an instrumentation amplifier with a gain of around 1000 (here comes a question into play, single or dual source?)
    - depending on the choice of the in-amp a single or dual voltage source
    - an ac-dc converter

    I have looked a numerous in-amps (analog devices AD620 etc.). However, all the specs showed a very simplistic picture of bridge amplification circuits. Is it really that simple?

    Would it be cheaper to buy a AC-DC to 10V converter and use a voltage divider to a achieve the +/- 5V I need for the in-amp or would it make more sense to buy a AC-DC +/- 5V converter?

    Would be great if you guys could give me your input on that!

    Thanks a lot.

  2. bertus


    Apr 5, 2008

    Take a look in the attached PDF on bridge circuits.

  3. manuu84

    Thread Starter New Member

    Jun 16, 2009

    thanks for your response. However, I might be wrong but I don't feel that my answers got answered completely. The article mainly discusses the advantage of ACDs for bridge conditioning. I'd like to read the signals as analog signals between -10 and 10 Volts.

    Any suggestions for the questions asked in the original thread?


  4. SgtWookie


    Jul 17, 2007
    You need to define your requirements a bit more here.
    Read through this instrumentation amplifier application note from Intersil:

    Then have a look at the INA128/INA129 instrumentation amplifiers from Texas Instruments/BurrBrown just for comparison:

    The amplifier you choose and your requirements will steer you towards the appropriate supply to use.
    For low noise, you'll probably want a linear supply rather than a switching supply.

    We have no clue where you live, so don't know what you might obtain at a reasonable cost.
  5. manuu84

    Thread Starter New Member

    Jun 16, 2009
    Hey, the problem is, I don't really know what voltage I'll need. The specs define the excitation impedance as 350 Ohms. How do I determine the voltage I need?

    I took a look at copied a diagram that was given in the pdf. Is it going to be that primitive?

    Well, this exaclty is my problem. I am trying to find out what requirements I have? The question is, in case I use a single source supply, I guess there is no way I'll get negative values for Vout, right? Since I need negative readings I guess I have to go for a dual supply?

    What kind of supplies or sources am I exactly looking for? It is desireably to keep it low cost.

    Thanks a lot.