A new approach to MWD inclination measurement: Direct Angle Measurement (DAM).
For decades, accelerometers have been the industry standard for MWD inclination measurement.
But there is one fundamental question worth asking:
Why do we continue to measure angles through acceleration?
An accelerometer does not measure inclination.
It measures acceleration.
The inclination angle is then calculated by extracting the Earth’s gravity vector (1g) from the total measured acceleration.
However, during drilling, the tool is continuously exposed to:
• Axial and lateral vibrations;
• Torsional oscillations;
• Shock loads;
• Dynamic tool motion.
To an accelerometer, all of these are simply acceleration.
It cannot determine which part of the measured signal comes from gravity and which part comes from drilling dynamics.
That is why every accelerometer-based inclinometer follows the same sequence:
Gravity + Vibrations + Shocks + Tool Dynamics
↓
Accelerometer
↓
Digital Signal Processing
↓
Inclination Angle
In other words:
An accelerometer-based inclinometer first measures everything happening to the drilling tool and only then attempts to mathematically recover the gravity vector.
A Different Measurement Philosophy
A fluid capacitive tilt sensor approaches the problem from a completely different direction.
Instead of measuring acceleration and calculating the angle, it measures the angle directly.
The sensing liquid naturally provides:
• Mechanical inertia;
• Viscous damping;
• Suppression of high-frequency vibrations and short-duration shock loads.
As a result, a significant portion of the unwanted dynamic disturbances is attenuated before the signal is converted into an electrical output.
The measurement chain is therefore fundamentally different:
Gravity
↓
Liquid Surface
↓
Mechanical Filtering
↓
Direct Angle Measurement
↓
Electrical Signal
In other words:
A fluid capacitive tilt sensor suppresses a significant part of the drilling dynamics before they ever become an electrical signal.
Key Advantages
- Direct angle measurement
- Accuracy up to 0.005°
- Mechanical suppression of vibrations before signal conversion
- No need to extract a 1g reference from a dynamically disturbed environment
- No temperature hysteresis
- Less than 0.1% non-linearity across the operating temperature range
- High shock resistance due to a simple sensing structure
- No long-term drift
The key difference between these two technologies is not only sensor performance.
It is the measurement philosophy.
Accelerometer:
Measure everything → Recover gravity → Calculate angle.
Direct Angle Measurement:
Physically suppress disturbances → Measure the angle directly.