Capacitive uterine contraction sensor

Abstract

A capacitive uterine contraction sensor ( 28 ) includes an insulating substrate ( 18 ), a first electrode ( 20 ) disposed on one side of the substrate ( 18 ), and a second electrode ( 22 ) positioned in a spaced relation to the first electrode ( 20 ). The second electrode ( 22 ) is configured to move toward or away from the first electrode ( 20 ). The sensor may also include a conductive standoff ( 24 ) sandwiched between the substrate ( 18 ) and the second electrode ( 22 ) for maintaining the second electrode ( 22 ) in a spaced relation to the first electrode ( 20 ). The conductive standoff ( 24 ) is electrically coupled to the second electrode ( 22 ) and electrically isolated from the first electrode ( 20 ). Alternatively, the second electrode ( 22 ) may include a spring mechanism used in conjunction with a standoff ( 24 ) to maintain the second electrode ( 22 ) in a spaced relation to the first electrode ( 20 ). The spring mechanism is electrically isolated from the first electrode ( 20 ) and enables the second electrode ( 22 ) to move toward or away from the first electrode ( 20 ).

1 . A capacitive uterine contraction sensor comprising: 
 an insulating substrate;    a first electrode disposed on one side of the substrate; and    a second electrode positioned on the first side of the substrate in a spaced relation to the first electrode, at least part of the second electrode configured to move toward or away from the first electrode.    
     
     
         2 . The sensor of  claim 1 , further comprising a conductive standoff sandwiched between the substrate and the second electrode for maintaining the second electrode in spaced relation to the first electrode, the conductive standoff electrically coupled to the second electrode and electrically isolated from the first electrode.  
     
     
         3 . The sensor of  claim 1 , wherein the second electrode comprises a spring mechanism, wherein the spring mechanism is electrically isolated from the first electrode, the second electrode maintained in spaced relation to the first electrode.  
     
     
         4 . The sensor of  claim 3 , wherein: 
 the second electrode includes a plurality of channels in a body;    a plurality of tabs extend from the body; and each tab is secured to the substrate via a standoff.    
     
     
         5 . The sensor of  claim 1 , further comprising a load transfer button positioned on a side of the second electrode facing away from the first electrode.  
     
     
         6 . The sensor of  claim 1 , further comprising electronic circuitry for determining a capacitance of a capacitor formed by the spaced relation of the first and second electrodes.  
     
     
         7 . The sensor of  claim 6 , further comprising means for communicating with an external monitoring unit.  
     
     
         8 . The sensor of  claim 1 , further comprising means for securing the capacitive uterine contraction sensor against an abdomen.  
     
     
         9 . The sensor of  claim 1 , further comprising a dielectric disposed between the first electrode and the second electrode.  
     
     
         10 . The sensor of  claim 1 , further comprising a conductive sheet on each side of the substrate, wherein: 
 the conductive sheets are electrically connected;    the first electrode is electrically isolated from the conductive sheet on the one side of the substrate; and    the second electrode is electrically connected to the conductive sheet on the one side of the substrate.