Non-intrusive pressure gage

A sensor system for detecting a change in condition, comprising:

• a radioactive source;
• a plurality of detectors configured to detect radiation emitted from the radioactive source;
• a displacement assembly configured to alter the position of the radioactive source in response to the change in condition;
• and
• wherein the displacement assembly comprises:
• a Bourdon tube;
• and
• a channel and a rolling element disposed in the channel, the position of the rolling element with respect to the channel defining the displacement of the source, and wherein the channel facilitates translation of rotational motion of the Bourdon tube into linear motion of the source.

A sensor system for detecting a change in condition of an annular region, comprising:

• first and second walls cooperative to define the annular region;
• a radioactive source disposed in the annular region;
• at least one radiation detector disposed outside the annular region and configured to detect radiation emitted by the radioactive source;
• a displacement assembly configured to physically displace in response to the change in condition and configured to change the radiation levels detected by the at least one radiation detector in response to such displacement;
• a shielding assembly;
• and
• wherein the displacement assembly is configured to physically displace the shielding assembly in response to the change in condition.

A method of detecting a change in condition, comprising:

• disposing a radioactive source on one side of a physical barrier;
• disposing at least one radiation detector configured to detect radiation from the source on an opposite side of the physical barrier;
• changing the radiation levels detected by the at least one radiation detector in response to the change in condition by physically displacing a shielding assembly in response to the change in condition;
• and
• quantifying the change in condition based on the radiation levels detected by the at least one detector.

A method of detecting a change in condition, comprising:

• disposing a radioactive source on one side of a physical barrier;
• disposing at least one radiation detector configured to detect radiation from the source on an opposite side of the physical barrier;
• changing the radiation levels detected by the at least one radiation detector in response to the change in condition by physically displacing a shielding assembly in response to the change in condition;
• and
• wherein the shielding assembly comprises a shield disposed between the radioactive source and the radiation detector, the shield comprising a first portion that facilitates a greater transmission of radiation from the radioactive source at a given distance from the source than a second portion of the shield at the given distance.

A sensor system for detecting a change in condition of an annular region, comprising:

• first and second casing strings cooperative to define the annular region;
• a radioactive source disposed in the annular region;
• a radiation detector disposed outside the annular region and configured to detect radiation emitted by the radioactive source;
• a shielding assembly configured to shield radiation emitted by the radioactive source;
• a displacement assembly configured to physically displace the shielding assembly in response to the change in condition to change the radiation levels detected by the radiation detector;
• and
• a processing device capable of receiving an input signal from the radiation detector and to produce the change in condition based on the input signal.