1. Point by point fiber optic methods
Plastic optical fibers are inserted at known distances along the explosive column. As the detonation wave passes, the light flash emitted by the detonation reaches each fiber tip and is conducted to the recorder. Dividing the inter fiber distance by the measured time of flight returns the average V.O.D over each interval.
Strengths. Completely insensitive to electromagnetic interference, well suited to the field, robust against water and harsh weather, simple installation, low cost consumables.
Limits. Provides one V.O.D value per interval rather than a continuous profile. Spatial resolution depends on the number of fibers used.
This is the method used by Kontinitro Explomet 2 Series, Explomet 3 and Detomet 2.0 instruments, with ±0.01 microsecond timing precision.
2. Continuous resistive probes
A resistive wire or coaxial probe is placed inside or alongside the explosive column. As the detonation front advances, the probe is progressively short circuited, returning a resistance versus time curve. Differentiating that curve yields a continuous V.O.D profile along the charge.
Strengths. Continuous profile, very high spatial resolution.
Limits. Sensitive to electromagnetic noise from electric detonators and nearby radio sources, more demanding setup, higher consumable cost per shot.
3. Photon Doppler Velocimetry (PDV)
A laser interferometer measures the Doppler shift of light reflected from a moving surface, typically the detonation front through a window or a probe. PDV returns a high resolution velocity history and is used in laboratory detonation physics and explosively driven experiments.
Strengths. Very high time and velocity resolution, contactless, suited to non self luminous experiments.
Limits. Laboratory equipment cost and complexity, line of sight requirement, not a field method.
Choosing a method
For routine V.O.D verification in production, blast hole monitoring in mining and quarries, and most field testing, fiber optic point by point methods offer the best balance of accuracy, robustness and operating cost. Continuous resistive probes complement them when a full V.O.D profile is required in a controlled laboratory context. PDV is the reference for detonation physics research.
See also the field testing, mining and quarries and energetic materials applications.