force sensor...

[Will McGonegal]

I design and build dynamometers at our emissions lab and we use load cells on most of
our dynamometers (engine and chassis).  We have been using the 'S' shape style most of
the time.  These load cells have a strain gage bridge on them to measure the force
applied through them at the end of a torque arm attached to the pivoting power
absorption unit (water brake in your case).  These units require a constant excitation
voltage (typically 10 volts) and the give a signal of about -30 to + 30 mV full scale
proportional to force.  We had a water brake dynamometer come in a few years ago with a
spring loaded wire-wound potentiometer (very large spring, dampened in oil) to measure
the force.  It was quickly replaced with a load cell.  These are simple and easy to use,
and very repeatable.

We have purchased from a few makers including:
Interface: 602 948-5555 Super Mini load cells (e.g.: SSM-AJ-1000)
HBM (Hottinger Baldwin Messtechnik): 508 624-4500
Omegadyne (http://www.omegadyne.com/) - LC101, LC105

Prices start around $300 US, maybe not so good for the home DIYer.

Will McGonegal
Project Engineer/Dynamometer Developer
Emissions Research and Measurement Division
Environment Canada

> From: "Daniel R. Henriksson" <rotax at ludd.luth.se>
> Date: Tue, 21 Jul 1998 16:28:12 +0200 (MET DST)
> Subject: Re: force sensor...
>
> I recently acuired a water-brake dynamometer.
> I'm now looking for some force sensing device,