公开(公告)号：US3863238A

公开(公告)日：1975-01-28

申请号：US17779471

申请日：1971-09-03

Applicant: HONEYWELL INC

Inventor： ROWELL WILLIAM G

IPC: G08B17/04 ,  G08B21/00

CPC classification number: G08B17/04

Abstract: A circuit for use with a sensor located in a hazardous area such as in an atmosphere of explosive gases, organized to prevent electrical power at the sensor from exceeding prescribed levels even upon reasonably foreseeable failures of parts of the circuit. The circuit, which is located in a non-hazardous area, includes an indicator, such as a relay-controlled alarm, to respond to the sensor, and terminals for connection to a source of line voltage. Two voltage step-down transformers have their secondaries connected in series with one another and with the sensor. The primary of one transformer is connected to the line voltage source; and the primary of the other transformer is connected to the indicator. Each transformer secondary lies intermediate a pair of current limiting resistors, and the primary and secondary windings of each transformer are isolated by means of a grounded conductive sheet. Each transformer, along with its associated current limiting secondary resistors, is embedded in potting material to form a self-contained isolating circuit module. The circuit is intended to be connected to a remote ground terminal as well as the ground terminal of the line voltage source. A ground integrity detector circuit interrelates these three terminals by means of resistances and a neon glow tube to provide a signal whenever one of the ground circuits is lost, as well as a signal upon failure of one of the resistances forming the ground integrity detection circuit. The remote ground connection has a path extending through the circuit chassis to insure that its ground is maintained.

Abstract translation: 一种用于传感器的电路，该传感器位于诸如爆炸性气体的危险区域中，其组织以防止传感器的电力超过规定的水平，即使在电路部件的合理可预见的故障。 位于非危险区域的电路包括一个指示器，例如继电器控制的报警器，用于响应传感器，以及用于连接到电源电压的端子。 两个降压变压器的二次互感器与传感器相互串联连接。 一个变压器的主要连接线路电压源; 并且另一个变压器的主要连接到指示器。 每个变压器次级位于一对限流电阻之间，每个变压器的初级和次级绕组通过接地的导电板隔离。 每个变压器及其相关的限流二次电阻器都嵌入灌封材料中以形成独立的隔离电路模块。 该电路旨在连接到远程接地端子以及线路电压源的接地端子。 接地完整性检测器电路通过电阻和氖辉光管将这三个端子相互关联，以便每当一个接地电路丢失时提供信号，以及在形成接地完整性检测电路的电阻之一发生故障时的信号。 远程接地连接具有延伸穿过电路底盘的路径，以确保其接地保持。