Electrical resistance monitoring device

• US 20030164770A1
• Filed: 04/25/2003
• Published: 09/04/2003
• Est. Priority Date: 07/29/2000
• Status: Active Grant

• Current Assignee: Newson Gale Ltd. (Hoerbiger-Stiftung)
• Original Assignee: Newson Gale Ltd. (Hoerbiger-Stiftung)
• Inventors: Edge, Ian James
• Granted Patent: US 6,924,740 B2
• Time in Patent Office: Days
• US Class Current: 340/635
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: H01R 11/24 with gripping jaws, e.g. crocodile clip

Abstract

There is described a device for indicating whether a conductive element has an electrical resistance equal to or less than a predetermined value or whether the conductive element is reliably connected to earth reference potential by a resistance equal to or less than a predetermined value. The device commonly takes the form of a grounding clamp (1) for connecting said device to the conductive element, the clamp (1) conveniently taking the form of a pair of spring loaded jaws (2, 3). The clamp (1) incorporates or is connected to a monitoring unit comprising a current-to-voltage converter with a voltage output proportional to the resistance of the conductive element, a comparator which determines at predetermined intervals whether said voltage output is equal to or less than a preset reference, and hence whether the measured resistance is equal to or less than the predetermined value, and signalling means (8) which are actuated to provide an indication as to whether the measured resistance is equal to or less than the predetermined value. The signalling means (8) is most conveniently a light emitting diode.

Claims

1. A device for indicating whether a conductive element has an electrical resistance equal to or less than a predetermined value or whether the conductive element is reliably connected to earth reference potential by a resistance equal to or less than a predetermined value, said device comprising

clamp means for connecting said device to the conductive element;

wherein said clamp means incorporate a battery powered monitoring unit comprising

a current-to-voltage converter with a voltage output proportional to the resistance of the conductive element;

a comparator which determines at predetermined intervals whether said voltage output is equal to or less than a pre-set reference, and hence whether the measured resistance is equal to or less than the predetermined value; and

signalling means which are actuated to provide an indication as to whether the measured resistance is equal to or less than the predetermined value, the predetermined value of the measured resistance being in the range 1-100 Ohms.

2. A device as claimed in Claim 1, wherein the clamp means comprises a pair of spring-loaded jaws which are engaged with an available part of the conductive element and contain contacts which are connected to the monitoring unit.

3. A device as claimed in claim 1 or claim 2, wherein the monitoring unit is housed in a remote enclosure to which the clamp means is connected.

4. A device as claimed in any preceding claim, wherein the predetermined value of the measured resistance is less than 50 Ohms.

5. A device as claimed in any preceding claim, wherein the signalling means is a visual signalling means.

6. A device as claimed in claim 5, wherein the signalling means is a lamp which is illuminated continuously or intermittently so long as the measured resistance has a value less than the predetermined value.

7. A device as claimed in claim 6, wherein the lamp is a light-emitting diode.

8. A device as claimed in any preceding claim, wherein the battery is a lithium manganese battery.

9. A device as claimed in any preceding claim, wherein the clamp means comprises a pair of spring-loaded jaws which are provided with three point contacts, one of said contacts being provided on one of the clamp jaws and the other two contacts on the other jaw.

10. A device as claimed in claim 9, wherein, when the clamp is closed, the two contacts on one jaw lie to either side of the single contact on the other jaw, the three contacts lying substantially in a common plane.

11. A device as claimed in claim 9 or claim 10, wherein the two contacts on one of the jaws make electrical contact with the equipment to which the clamp is applied and are connected to the monitoring unit, the third point contact on the other jaw being of insulating material.

12. A device as claimed in any preceding claim, wherein the clamp means is connected to earth by a cable.

13. A device as claimed in claim 12, wherein the cable is a two-core cable and the device is adapted to monitor both the connection of the device to the conductive element to which it is applied and also the connection of the device to earth.

14. A device as claimed in claim 12, wherein the cable is a single-core cable and the device is adapted to monitor only the connection of the device to the conductive element to which it is applied.