Detonator delay measurement
Pyrotechnic and electric detonators, why measuring real delays matters, and how the shock tube signal speed is characterized.
Two families of detonators
Civilian and industrial blasting uses two main detonator families. Pyrotechnic detonators rely on a combustible delay element whose burning time defines the delay. Electronic detonators replace that element with a programmable timer driven by an integrated circuit.
Both families are initiated through a shock tube, an electric line or a wireless system. Once the initiation signal reaches the detonator, a measurable interval passes before the base charge detonates. That interval is the detonator delay.
Why delays must be measured ?
Blast design relies on precisely timed detonations to control fragmentation, ground vibration, airblast overpressure and throw. A drift of a few milliseconds across a sequence can re collide rock columns, increase backbreak or cause flyrock. Even a few percent error on a key hole can change the outcome of a tunnel face advance.
Manufacturers measure delays to validate production, document conformity and audit shelf life. End users measure the delays of representative lots before critical blasts, especially when working close to sensitive infrastructure.
Measuring shock tube speed
The shock tube is itself a timing element. Its signal travels at a finite speed, typically between about 1,800 and 2,200 meters per second, but the actual speed in a specific roll or installation may deviate from the published value. Measuring it removes a hidden source of error from any delay calculation. The Detomet 4 supports this measurement directly.
The Kontinitro approach
The Detomet 4 measures the delay of one to five non electric or electric detonators initiated by shock tube, with a timing precision of 0.01 microsecond. Fiber optic sensors detect the light flash at initiation and at detonation, and the unit returns the interval directly. The graphical display allows a configurable preliminary review, and all results are stored on SD card.
For larger campaigns, the Detomet High Capacity system extends the same architecture to 20, 24 or 30 channels in a heavy duty transport case.
FAQ
Common questions
What is a detonator delay ?
The delay is the time interval between the arrival of the input signal at the detonator, usually via a shock tube or power line, and the actual detonation of the base charge. Delays allow shot designers to stagger the holes to control fragmentation, vibration, and projection.
Why measure detonator delay ?
Nominal delays remain nominal. Pyrotechnic delay elements are subject to manufacturing tolerances, aging, and storage conditions, while electronic detonators have programming and triggering tolerances. Measuring actual delays allows manufacturers to validate quality and end users to audit batches before critical firings.
How is the delay measured ?
An optical or electrical sensor detects the initiation signal, and then a second sensor detects the actual detonation. The instrument records the time interval with submicrosecond accuracy. The Kontinitro Detomet 4 uses fiber optic detection of the light flash at initiation and detonation, and records the delays of one to five detonators in a single measurement, with an accuracy of ±0.01 microseconds.