Identification of Bizarre Load Cell- Help Needed

Discussion in 'The Projects Forum' started by MrFisher, Jun 21, 2010.

  1. MrFisher

    Thread Starter New Member

    Jun 21, 2010
    Hello all,
    I'm currently doing some work for an osteopathic clinical center in my area, where I'm tearing into a clinical measurement tool called the "Isostation B-200", by IsoTechnologies. The company is long out of business, but what we're looking to do is tap into the torque load cells which measure torque on the 3 axes of rotation of the device.

    I think the load cells may be custom-made in house by IsoTechnologies, as there are no serial numbers or manufacturer information on them whatsoever. One of them is has the string "MSI-10" machined into it, while another has "MI7" scratched into the bottom. I've been unable to locate any information whatsoever about either the company or load cells with this information. All three load cells have 4 wires coming out of them- red, black, green, and white, which I understand to be standard for full-bridge sensors.

    I'm familiar with working on full-bridge strain gage systems, and we currently have an NI-9237 for amplification and reading of the bridge voltages. However, unlike any other gauges I've ever looked at, the resistances of these load cells are bizarre. The resistances I've measured, which are consistent between all the load cells, are:
    Red-White: 12 KOhm
    Red-Black: 15 KOhm
    Red-Green: 15 KOhm

    White-Black: 15 KOhm
    White-Green: 15 KOhm

    Black-Green: 22 KOhm

    Not only are these resistances HUGE compared to any other gauges I've seen, the pattern isn't even consistent with a full-bridge circuit.

    A manual I found for another load cell suggested that the largest resistance is typically between the excitation wires, so I connected it that way just to test. I get readings out of the cell, but they're incredibly bad, with massive "ringing" during transient loading, and poor correspondence in general to what I'm doing to the cell.

    I'm hoping someone here has some idea what's going on with this load cell. Is it perhaps a piezoelectric system? What should I be trying next? Thanks for any help!
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    I think it would be better to show a picture. That way atleast a weak memory might be triggered in one of the members.
    As for the load cell. I am not familiar with it, but if I see it then at least we can discuss it further more.