Cathodic protection waveform monitoring unit with asynchronous monitoring

Abstract

A method and system is disclosed for testing a cathodic protection system that protects a metallic structure with one or more DC power sources electrically connected to the metallic structure and an associated reference electrode. The metallic structure may be cathodically protected at multiple locations. A Cathodic Protection Waveform Monitoring Unit (CPWMU) operates independently from power cycling by the cathodic protection system to measure cathodic protection voltage levels by measuring, over one or more measurement time periods, a voltage differential between the metallic structure and its associated reference electrode, a plurality of times when power provided to the metallic structure is cycled on and off. The CPWMU includes digital storage to store values indicative of the measured voltage differentials over the measurement time period. A Cathodic Protection Waveform Reader (CPWR) that may be remotely located from any CPWMU communicates with a number of CPWMU's within communication range to obtain the values stored in the CPWMUs. The CPWR may be positioned in a variety of aircraft, vehicles or be hand carried.

What is claimed is: 
     
         1 . A method for testing a cathodic protection system for a metallic structure, that has associated therewith at each of a first set of locations, a testing module electrically connected to the metallic structure and an associated reference electrode, the method comprising:
 periodically, at a first frequency, interrupting power provided at each of the first set of locations to cause power provided to the metallic structure to switch on and off a plurality of times over a testing time period;   measuring, by each testing module, a plurality of times during a plurality of interruption cycles, voltage differentials between the metallic structure and its associated reference electrode when the power provided to the metallic structure is on and when the power provided to the metallic structure is off, wherein initiation of each of the interruption cycles is independent of interrupting power provided at each of the first set of locations;   storing in a digital storage medium at each testing module, digital values associated with the measured voltage differentials during the interruption cycles; and   providing at least selected digital values to a remotely located device upon request by the remotely located device.   
     
     
         2 . The method set forth in  claim 1  wherein measuring, by each testing module, voltage differentials between the metallic structure and its associated reference electrode when the power provided to the metallic structure is on and when the power provided to the metallic structure is off is initiated after initiation of the testing time period. 
     
     
         3 . The method set forth in  claim 1  wherein measuring, by each testing module, a voltage differential between the metallic structure and its associated reference electrode a plurality of times during a plurality of interruption cycles is performed periodically at a frequency greater than the first frequency. 
     
     
         4 . The method set forth in  claim 1  wherein providing at least selected digital values to a remotely located device upon request by the remotely located device comprises providing digital values generated from the most recent interruption cycle. 
     
     
         5 . The method set forth in  claim 1  wherein the cathodic protection system further comprises a second set of locations that each include a testing module electrically connected to a coupon and an associated reference electrode, the method further comprising:
 measuring, by each testing module at the second set of locations, a voltage differential between the coupon and its associated reference electrode, a plurality of times over a plurality of interruption cycles; 
 storing in a digital storage at each testing module at the second set of locations, digital values associated with the measured voltage differentials during the measurement time period; and 
 providing the digital values to a remotely located device upon request by the remotely located device. 
 
     
     
         6 . A cathodic protection waveform monitoring unit comprising:
 a first input adapted for electrical connection to a reference electrode associated with a location on a first metallic structure protected by a cathodic protection system;   a second input adapted for electrical connection to the first metallic structure;   an A/D converter that converts time varying analog voltage levels provided by the first and second inputs to digitally encoded values indicative of voltage levels between the first metallic structure and the reference electrode;   data storage; and   a processor operatively coupled to the data storage, the processor configured to execute instructions that when executed cause the processor to:
 generate a first start test signal to store first digitally encoded values indicative of voltage levels during a period of time when a DC voltage applied to the first metallic structure is cycled on and off, wherein the start test signal is generated independently of initiation of a period of time when a DC voltage applied to the first metallic structure is cycled on and off; 
 generate a first stop test signal to stop storing the first digitally encoded values; and 
 generate a response to an upload signal to cause transmission of at least a subset of the first digitally encoded values to a requesting device. 
   
     
     
         7 . A cathodic protection waveform monitoring unit as set forth in  claim 6  further comprising:
 a third input adapted for connection to a metallic coupon associated with a location on the first metallic structure; and 
 a selector for selecting between the third input and the second input. 
 
     
     
         8 . The cathodic protection waveform monitoring unit as set forth in  claim 6  wherein the processor is further configured to execute instructions that when executed cause the processor to:
 generate a command to overwrite the oldest first digitally encoded values when the data storage is at capacity. 
 
     
     
         9 . The cathodic protection waveform monitoring unit as set forth in  claim 6  wherein the first input and the second input comprise a first channel corresponding to the first metallic structure and wherein the cathodic protection waveform monitoring unit further comprises a second channel comprising:
 a fourth input adapted for electrical connection to a reference electrode associated with a location on a second metallic structure protected by a cathodic protection system; 
 a fifth input adapted for electrical connection to the second metallic structure; and 
 wherein the processor is further configured to execute instructions that when executed cause the processor to: 
 generate a second start test signal to store digitally encoded values indicative of voltage levels during a period of time when a DC voltage applied to the second metallic structure is cycled on and off, wherein the second start test signal is generated independently of initiation of a period of time when a DC voltage applied to the second metallic structure is cycled on and off; 
 generate a second stop test signal to stop storing the digitally encoded values; and 
 generate a response to an upload signal to cause transmission of at least a subset of the second digitally encoded values to a requesting device. 
 
     
     
         10 . The cathodic protection waveform monitoring unit as set forth in  claim 9  further comprising:
 a sixth input adapted for connection to a metallic coupon associated with a location on the second metallic structure; and 
 a selector for selecting between the sixth input and the fifth input. 
 
     
     
         11 . The cathodic protection waveform monitoring unit as set forth in  claim 6  wherein the cathodic protection waveform monitoring unit is powered at least in part by a battery and wherein the battery has associated therewith a power scavenging means operable to derive energy from an external ambient source. 
     
     
         12 . A system for testing cathodic protection potential on a metallic structure wherein each of the locations has one or more galvanic or impressed current anodes connected to the metallic structure, comprising at least at a plurality of locations:
 an interrupter at each location operable to periodically switch electrical energy applied to the metallic structure on and off;   testing means, responsive to the switching means, for measuring a voltage differential between the metallic structure, or alternatively a metallic coupon if installed at a location with which the testing means is associated, and an associated reference electrode at a plurality of points in time that span multiple interruption cycles of power being switched on and off to each DC power supply;   data storage for storing digital values indicative of the voltage differentials measured by the testing means; and   data transfer means, responsive to a data request, for providing a selected subset of the stored digital values to a remote device.   
     
     
         13 . The system of  claim 12  wherein the selected subset of the stored digital values comprises values corresponding to a timestamp indicative of most recently stored values.