Electrical Testing Instruments for use Initiating Electrical Circuits

DOE-HDBK-1092-98

5.1.6.7.3 ELECTRICAL TESTING INSTRUMENTS FOR USE WITH INITIATING

ELECTRICAL CIRCUITS

Instruments used with electrical initiating circuits connected to electroexplosive devices may be

further categorized for use with either low-energy initiators or high-energy initiators. All testing

instruments used for this purpose shall be current-limited. Before being used on initiating circuits,

every instrument wiring diagram and internal circuitry design shall be analyzed, examined, and

certified for the following:

1. The output current through a resistance equivalent to that of the minimum resistance initiator

of the class shall not exceed 1% and shall not exceed 10% of the no-fire rating for the most

sensitive initiator of the class. The current-limiting features of the testing instrument shall be

internal to the instrument and shall not depend on the circuit load characteristics.

2. The internal circuitry shall ensure isolation features that require, at a minimum, two

independent failure modes before the specified output current can be exceeded.

3. A comprehensive (point-to-point, if possible) wiring check shall be made to ensure that the

wiring corresponds to the diagram and that all components are functioning properly and

within specifications.

5.1.6.7.4 ELECTRICAL TESTING INSTRUMENTS FOR USE WITH NONINITIATING

ELECTRICAL CIRCUITS

Testing instruments in this category are used with electric circuits connected to instruments such as

strain gauges, pin switches, pressure transducers, thermocouples, and electrical components that are

affixed to or within an assembly with explosives. These instruments shall meet the following

requirements:

1. Each use of the testing instrument shall be analyzed to ensure that there is no credible scenario

where the normal test energy from the testing instrument can ignite explosive charges or

initiators in the test. This testing shall be consistent with Section 5.1.6.7.3.

2. Where a testing instrument is used to make measurements on sensors directly applied to

explosives (e.g., bonded strain gauges or pin switches), the testing instrument shall be

certified and controlled.

3. Testing instruments shall be prominently marked with restrictions on their use. Many of these

testing instruments do not meet the requirements for use with initiating systems and shall be

marked to prevent their use on this type of circuit.

5.2 PREVENTION OF EXTERNAL IGNITION AND EXPLOSION

Explosives are hazardous by themselves, but around electricity they become even more dangerous:

an arc, spark, or hot surface can easily touch off an explosion. Therefore, the electrical installation

shall contain these ignition sources or house them in an area well separated from the explosives

storage area.

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