Isometric Force Transducers

Request Quotation

#159901A Radnoti Isometric Force Transducer

The Radnoti 159901A transducer operates on the principle of converting picofarad capacitance changes into an amplified DC output voltage by means of a patented circuit (U.S. Patent Number 4142144). The transducer consists of a stiff beam suspended between two capacitor plates. This forms a differential capacitor. Using this principal, the beam can be exceptionally stiff, approaching the ideal of measuring force without motion. As an example, for a force of 2 grams, the beam deflection is a maximum of only 5 microns in either the 0.2 or 2.0 gram range mode. The linearity is within +1% with a high DC voltage output and freedom from drift. The transducer comes with an integral short, rigid mounting handle. To obtain maximum advantage of stiff beam characteristics of the transducer, it should be positioned and held in place with hardware that is as rigid as possible such that all the muscle forces are recorded (i.e. captured) and none are lost in extraneous deflections of the mounting hardware. The 159951 series of Radnoti Support Stands are the mounting hardware of choice. The durable construction will not deflect under load. The transducer itself should be positioned such that the output cable at the rear of the transducer ends up on the bottom. The transducer has a short tissue mounting rod with a groove that projects from the front. One end of a non-stretching string or wire must be formed into a loop and fastened into the groove on the shaft. The other end of the string or wire is subsequently attached to the muscle preparation. The string or wire must be at right angle to the transducer rod and be pulled straight down once the final setup has been completed. The transducer is equipped with a transparent, removable plastic shield that helps to prevent buildup of salts (i.e. corrosives) which may otherwise tend to accumulate on the transducer rod and migrate into the transducer circuit. In time, this salt buildup can deteriorate performance. The wire or string from the beam must be directed through the slot in the splash shield without touching the edges.

#159906 Radnoti Transducer Positioner

The Radnoti transducer positioner uses a finely-threaded drive conveniently adjusted via a finger crank to precisely adjust the high sensitivity Isometric Transducer. Coarse adjustments are made by depressing the drive disengagement button and sliding the transducer mounting collar into approximate position. The positioner frame has a 1/2" clamping mechanism with lock-down screws at either end that permit the positioner to be slid and secured on a support rod or easily removed without dismantling the balance of equipment connected to the rod. The transducer is mounted to the positioner via a collar with a 1/2" hole secured with a thumbscrew, allowing horizontal movement of the transducer by sliding the transducer support rod through the collar.

#GR-FT03 Grass Isometric Force Transducer

* Four-arm bonded strain gauge elements
* Very high stability, accurate to ±1%
* Resolution as high as 25,000 to 1
* Exclusive patented multi range* springs extend useful range from milligrams to kilograms.
* May be connected for differential forces
* Heavy integral clamping handle - will take lots of abuse
* No microphonics - single dimension gravitational effects

Applications
The FT03 and FT10 Transducers were developed to measure muscle contractions isometrically. The ranges cover applications from single fibres to whole cat legs. Isotonic measurements can be made with externally applied springs.

Description
Four-bonded strain gages form a rugged bridge which measures the strain produced on a cantilever beam by the force applied. The housing is rugged and the handle can be clamped. Gravity effects are reduced to one dimension. High natural resonance is afforded by the cantilever. There are no pivots - no friction.

Features
Both transducer models are supplied with three sets of range springs providing four ranges. This yields maximum working ranges of over 40 to 1 for the FT03, and 100 to 1 for the FT10, extending applications. The FT10 is designed for the heavier forces. The FT03 has the most useful ranges for a general purpose transducer. With Grass Polygraphs the FT03 gives full scale deflection with the application of a few milligrams of force.

An eye is provided on the beam shafts on each side of the cantilever to facilitate attachment to the preparation. Differential forces can be measured by connecting the gage between forces applied to the two beam shafts. Also, an initial load can be applied and static forces can be balanced out to measure only the changing forces. The gages can be used to measure compression as well as tension.