Transducer for measuring dynamic translation by differential variable reluctance

Abstract

A differential variable reluctance transducer (DVRT) is provided to measure a translation parameter, such as acceleration and/or deceleration of a test projectile. The DVRT, contained in a canister of the projectile, includes a cylindrical housing and an electronics module. The housing defines a cavity containing insulation and a bobbin around which a wire coil is wrapped. The housing has an attachment end and a distal end that faces the acceleration indicator. The bobbin is disposed substantially collinear to the housing. The wire coil is helically disposed around the bobbin. The insulation fills the remainder of the cavity. The electronics module receives electric current from the wire coil and connects to a data recorder.

1. A differential variable reluctance transducer (DVRT) for measuring a translation parameter of a neighboring component in a high-acceleration environment, the DVRT comprising:
 a cylindrical housing that defines a cavity containing a bobbin substantially collinear with the housing, a wire coil helically disposed around the bobbin, an insulation otherwise filling the cavity, the housing having a distal end and an attachment end;  
 a membrane that covers the distal end of the housing;  
 an electronics module for receiving an electric signal from the wire coil, the electronics module terminating in an electrical connector to a data recorder; and  
 a cable connecting the housing to the electronics module,  
 wherein the electronics module provides a direct current (DC) output and comprises:  
 a frequency selector including a resistance and capacitor connected in parallel to a selection input;  
 a signal oscillator that receives the selection input from the frequency selector to produce a signal input;  
 an inductance-resistance Wheatstone bridge that receives the signal input from the signal oscillator at a junction tap of an inductor pair;  
 a demodulator that receives calibration and measurement signals from the Wheatstone bridge; and  
 a DC amplifier that receives and differences the calibration and measurement signals and that sends the electronic signal as the DC output.  
 
     
     
       2. The DVRT according to  claim 1 , wherein the housing and the membrane are comprised of stainless steel. 
     
     
       3. The DVRT according to  claim 1 , wherein the insulation is comprised of epoxy. 
     
     
       4. The DVRT according to  claim 1 , wherein the housing includes grooves along a surface of the cavity, the grooves being in physical contact with the insulation. 
     
     
       5. The DVRT according to  claim 1 , wherein the housing has a longitudinal length of 1.27 inches and a diameter of 0.94 inch, and the cable has a length of 2.5 inches. 
     
     
       6. The DVRT according to  claim 1 , wherein the translation parameter is one of displacement, velocity, acceleration and deceleration. 
     
     
       7. The DVRT according to  claim 1 , wherein the signal oscillator is a resistance-capacitance (RC) oscillator. 
     
     
       8. The DVRT according to  claim 1 , wherein the demodulator includes a matching pair of semiconductor diodes in parallel. 
     
     
       9. The DVRT according to  claim 1 , further comprising:
 an offset potentiometer that connects between an output from the demodulator and an input to the amplifier.  
 
     
     
       10. The DVRT according to  claim 1 , further comprising:
 a gain potentiometer that connects between an output from the demodulator and the DC output.