Method and apparatus to measure borehole pressure during blasting

A pressure sensing apparatus for measuring borehole pressure during blasting operations, comprising:

• at least one piezoelectric device encapsulated inside a molded structure, the molded structure including:
• a main portion;
• and
• a lead wire support;
• a pair of wire leads electrically coupled with the piezoelectric device, a first portion of each wire lead being encapsulated inside the molded structure and a second portion of each wire lead being outside of the molded structure;
• wherein the lead wire support includes at least one hole disposed on a top surface thereof to expose a portion of the wire leads and provide strain relief for the wire leads;
• and
• wherein the main portion of the molded structure includes an elongated profile with a substantially flat face that lies in a first plane, the piezoelectric device including a sensing face that lies in a second plane that is generally oriented parallel to the first plane.

A method of calibrating a pressure sensing apparatus for measuring borehole pressure during blasting operations, the method comprising:

• striking a first piezoelectric sensor of a first unmolded pressure sensing apparatus;
• determining, with an interference circuit, a first peak voltage of the first piezoelectric sensor during the striking thereof;
• striking a second piezoelectric sensor of a second molded pressure sensing apparatus;
• determining with the interference circuit, a second peak voltage of the second piezoelectric sensor during the striking thereof;
• and
• calculating a piezoelectric constant of the first piezoelectric sensor from at least the first and second peak voltages.