Fig.: Structure of the NV center: top: the diamond crystal; bottom: the NV center with N=nitrogen and V=missing carbon (vacancy).

How does NV diamond sensing work?

NV sensors use special Nitrogen-Vacancy centers (NV centers) in the diamond crystal that are extremely sensitive to magnetic fields, electrical and thermal influences. These quantum defects are optically excited by a green laser – the generated fluorescence depends on the local magnetic field and is read out via optical fiber.

Main advantages: contactless, galvanically isolated, robust against electromagnetic interference, measurement of DC and AC quantities as well as temperatures possible in extremely harsh environments
Measurement is microwave-free (no heat input into the object, high safety in high-voltage applications)
Isotope magnetic field measurement: Determines the magnitude |B| directly and spatially resolved

Fig.: AMA Innovation Award 2023

Applications and Unique Selling Points

Galvanically isolated high-voltage and current measurement
Galvanically and thermally isolated highly accurate position sensing in the most difficult environments
Magnetic field and eddy current cameras: visual representation of magnetic phenomena in real time
Miniaturized sensor heads that can be used in medical catheters, between cables or in hard-to-reach industrial facilities
Robust design, suitable for temperatures from −100 °C (probably lower) to +250 °C (probably higher) and aggressive chemicals or use in particle radiation
Diverse applications from material testing, motor monitoring to research, life sciences and defense

More technical details and examples can be found in the official technology handout (PDF) by Quantum Technologies.

Benefits at a Glance

Contactless, galvanically and thermally isolated position, current and magnetic field measurement – robust, fast, at room temperature, without microwaves even in the most difficult atomic, chemical, biological, thermal environments.

How it works

The control unit causes a light source, e.g. an LED, to emit modulated green light.
The green light excites NV centers in the diamond.
The NV centers fluoresce red; the fluorescence intensity depends on the magnetic field B.
The field-dependent red fluorescence is guided, e.g., via optical fiber to the evaluation unit.
The field-dependent red fluorescence is typically separated there from the green light.
The field-dependent red fluorescence is detected by a photodetector.
The control unit detects the fluorescence change attributable to the magnetic field.
The control unit derives one or more measured values from this – galvanically and thermally isolated from the measuring point.

Fig.: Basic principle: green light → red fluorescing diamond → field-dependent signal.

Why microwave-free?

Less complexity: no microwave generator or antenna required → more compact, cost-effective setup.
Active EMC friendliness: no active microwave source, low interference.
Passive EMC friendliness: no antenna effect due to missing microwave feed line.
Energy efficient: lower power consumption, no self-heating.
Robustness: fewer components → higher reliability and dependability.
Cost advantage: simpler design, signal evaluation less complicated, packaging and integration faster and cheaper.
Better suited for mass production, CMOS integration (low-power) and HV integration.

Applications

Current measurement (e.g. HV batteries, inverters, DC link)
Current density distribution (electrochemistry etc.)
EMC diagnostics and magnetic field monitoring
Magnetic field imaging (prototyping, QA, field distributions)
Condition monitoring in machines and systems
Position detection under the most difficult conditions
(medicine, industry, mining, drilling technology, defense, automotive, avionics)
Control and protection (e.g. wide-bandgap switches, optical fuses)

Material & Design Options

Basic types:

• Single-crystal diamond (sc-C): uniform lattice, NV axes defined, high sensitivity

• oriented crystal: NV centers preferentially oriented (e.g. ⟨111⟩); no smooth curve; use of spikes for measurement; magnetic field must be stabilized.
• oriented crystal: NV centers stochastically distributed in four orientations in the crystal: four preferred orientations (difficult to useless). No smooth curve.

• Polycrystalline (pc-C): many grains with different orientations; NV axes stochastically distributed over the volume; smooth measurement curves; use of the entire curve; bias magnetic field not necessary (= cost-effective)

Advantages and disadvantages:

Variant	Advantages	Disadvantages
Single crystal, oriented and NV centers oriented	Vectorial measurement (3D), highest homogeneity/sensitivity, self-calibrating, good physical reproducibility, very low processability for series production	Expensive, complex manufacturing & orientation to microradian accuracy, sensitive to misalignment and fluctuations, only for niche markets
Single crystal, oriented and NV centers not oriented	Vectorial measurement (3D), high homogeneity/sensitivity, self-calibrating, good physical reproducibility, very low processability for series production	Expensive, complex manufacturing & orientation to microradian accuracy, sensitive to misalignment and fluctuations, only for niche markets
Polycrystalline, stochastic	Very robust, cost-effective, best mass integration option, isotropic scalar measurement, high NV density	Lower sensitivity, broader lines, self-calibrating systems possible, less suitable for precise vector analyses, very good for mass markets in areas where Hall, TMR, and GMR sensors do not work.
Polycrystalline, partially oriented	Very robust, cost-effective, best mass integration option, isotropic scalar measurement and anisotropic vectorial measurement possible with one substrate, high NV density	Lower sensitivity, broader lines, self-calibrating systems possible, suitable for simple vector analyses, very good for mass markets in areas where Hall, TMR, and GMR sensors do not work.

Practical conclusion: For scalar, microwave-free current/magnetic field measurement in harsh HV environments, polycrystalline, stochastically distributed NV media are ideal (first choice for series production). For highest sensitivity and highly precise vector measurement, single-crystal, oriented NV media are suitable.

Performance Data & Integration

Bandwidth: From DC to high frequency (design-dependent, up to several MHz)
Response time: Down to the nanosecond range
Isolation: e.g. optical fiber or other optical systems, high galvanic, thermal and radiation isolation
Temperature range: −100 °C to +250 °C, radiation stable (e.g. fusion/X-ray environment)
Form factors: Sensor elements in fiber-coupled variants possible with <50 µm diameter
Form factors: Sensors (sensor element incl. electronics) from sugar cube to fingertip size, arrays, fiber-coupled variants
Integration: CMOS/MOEMS-compatible, suitable for miniaturized systems and arrays

Advantages of NV Diamond Sensing (compact)

Room temperature operation, no cryogenic need
High isolation (galvanic, thermal, radiation)
In current measurement contactless/shuntless → no line losses, no self-heating
Metal-free actuation & readout – no arcing hazard, optimized for air gap/transformer/EMC
Fast (ns), wide bandwidth (DC-MHz+)
Mechanically, chemically robust (diamond)
Low drift & tolerant in scalar measurements
Miniaturizable
for flexible array/camera concepts (from a few µm² up to several m²)
also suitable for magnetic field distribution measurement on curved surfaces
Long measurement paths from electronics to sensor element possible
high distance sensitivity sensor element to sample
Future-proof: proprietary IP, partners from industry & science

IP & Partners

Intellectual property rights to key technologies and design variants lie with Quantum Technologies
Strong contractual partnerships with academic and industrial R&D partners
Long-term roadmap for industrial integration and technology leadership

Would you like a technical discussion, a sample, or a personal demo?
Contact us: info@quantumtechnologies.de | Tel.: +49 341 69764090