Sensor system for an impressed cathodic protection circuit

• US 4,219,807 A
• Filed: 04/17/1978
• Issued: 08/26/1980
• Est. Priority Date: 04/17/1978
• Status: Expired due to Term

• Current Assignee: Cathodic Protection Services Incorporated
• Original Assignee: Cathodic Protection Services Incorporated
• Inventors: Speck, Robert M., Beil, Lawrence E.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/896,954
• Time in Patent Office: 862 Days
• Field of Search: 340/664, 340/663, 340/691, 340/693, 340/507, 307/95, 324/72, 324/65 CR, 324/64
• US Class Current: 340/664
• CPC Class Codes: C23F 13/04 Controlling or regulating desired parameters
• CPC Class Codes: G01R 19/16571 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00

Abstract

The sensor system senses a drop in the flow of impressed cathodic protection current to a minimum threshold level. A potential difference is developed which is a sample of the cathodic protection current. A comparator receives the sample potential difference and normally produces an output control signal which drops to substantially zero when the cathodic protection current drops to a predetermined threshold level. A relay responsive to the control signal then switches a signaling device to its signaling condition. A standby battery is also coupled to the signaling device through the relay. In the event of any failure in the sensor system or in the primary source of power energizing the sensor system, the standby battery becomes connected to the signaling device to cause it to change to its signaling condition.

Claims

1. A surveillance apparatus for instantaneously sensing a cathodic protection current flowing in a cathodic protection circuit, comprising:

an energizing circuit including a regulator network connected to a primary source of energy, said network converting the receiving energy to a useful, direct-current potential for impressing a sufficient cathodic protection current to a conductor subject to corrosion;

a potentiometer connected in parallel with a branch of said cathodic protection circuit, said potentiometer having a pair of output terminals and an adjustable center tap for developing an adjustable potential difference between said output terminals;

a comparator having an output terminal and a pair of input terminals connected to said output terminals of said potentiometer for instantaneously sensing the potential difference therebetween;

a storage battery;

a switching network having a first input connected to the output of said comparator, and a second input connected to said energizing circuit and to said storage battery; and

a signaling device having a pair of input terminals connected through said switching network to said energizing circuit and to said storage battery, said signaling device becoming energized either by said energizing circuit or by said storage battery depending on the condition of said switching means, said signaling device having a non-signaling state when said potential difference is above a threshold level, and a signaling state when said potential difference drops to said threshold level.

2. The surveillance apparatus of claim 1, wherein said signal emitter emits a visible signal, and, said visible signal emitter has said signaling and non-signaling states.

3. The apparatus of claim 2, wherein said visible signal emitter has colored shutters whereby the colors of said shutters are remotely visible when said signal emitter is in its signaling state.