digital-brain/content/zettels/position_sensors.md

+++ title = "Position Sensors" author = ["Thomas Dehaeze"] draft = false +++

Tags

[Inertial Sensors]({{<relref "inertial_sensors.md#" >}}), [Force Sensors]({{<relref "force_sensors.md#" >}}), [Sensor Fusion]({{<relref "sensor_fusion.md#" >}}), [Signal Conditioner]({{<relref "signal_conditioner.md#" >}}), [Signal to Noise Ratio]({{<relref "signal_to_noise_ratio.md#" >}})

Types of Positioning sensors

High precision positioning sensors include:

• [Interferometers]({{<relref "interferometers.md#" >}})
• [Capacitive Sensors]({{<relref "capacitive_sensors.md#" >}})
• [LVDT]({{<relref "linear_variable_differential_transformers.md#" >}})
• [Eddy Current Sensors]({{<relref "eddy_current_sensors.md#" >}})
• [Encoders]({{<relref "encoders.md#" >}})

Reviews of Relative Position Sensors

• Fleming, A. J., A review of nanometer resolution position sensors: operation and performance (Fleming 2013) ([Notes]({{<relref "fleming13_review_nanom_resol_posit_sensor.md#" >}}))

Table 1: Characteristics of relative measurement sensors collette11_review

Technology	Frequency	Resolution	Range	T Range
LVDT	DC-200 Hz	10 nm rms	1-10 mm	-50,100 °C
Eddy current	5 kHz	0.1-100 nm rms	0.5-55 mm	-50,100 °C
Capacitive	DC-100 kHz	0.05-50 nm rms	50 nm - 1 cm	-40,100 °C
Interferometer	300 kHz	0.1 nm rms	10 cm	-250,100 °C
Encoder	DC-1 MHz	1 nm rms	7-27 mm	0,40 °C
Bragg Fibers	DC-150 Hz	0.3 nm rms	3.5 cm	-30,80 °C

Table 2: Summary of position sensor characteristics. The dynamic range (DNR) and resolution are approximations based on a full-scale range of 100um and a first order bandwidth of \(1 kHz\) fleming13_review_nanom_resol_posit_sensor

Sensor Type	Range	DNR	Resolution	Max. BW	Accuracy
Metal foil	\(10-500 \mu m\)	230 ppm	23 nm	1-10 kHz	1% FSR
Piezoresistive	\(1-500 \mu m\)	5 ppm	0.5 nm	>100 kHz	1% FSR
Capacitive	\(10 \mu m\) to \(10 mm\)	24 ppm	2.4 nm	100 kHz	0.1% FSR
Electrothermal	\(10 \mu m\) to \(1 mm\)	100 ppm	10 nm	10 kHz	1% FSR
Eddy current	\(100 \mu m\) to \(80 mm\)	10 ppm	1 nm	40 kHz	0.1% FSR
LVDT	\(0.5-500 mm\)	10 ppm	5 nm	1 kHz	0.25% FSR
Interferometer	Meters		0.5 nm	>100kHz	1 ppm FSR
Encoder	Meters		6 nm	>100kHz	5 ppm FSR

Capacitive Sensors and Eddy-Current sensors are compare here.

{{< figure src="/ox-hugo/position_sensors_thurner15.png" caption="Figure 1: Overview of range and precision of different position displacement sensors. Taken from <sup id="53230532ada812541a7cd984b3aa2662"><a href="#thurner15_fiber_based_distan_sensin_inter" title="Thurner, Quacquarelli, Braun, Pierre-Fran\ccois, Dal Savio, Karrai &amp; Khaled, Fiber-Based Distance Sensing Interferometry, {Applied optics}, v(10), 3051--3063 (2015).">thurner15_fiber_based_distan_sensin_inter" >}}

Bibliography

Fleming, Andrew J. 2013. “A Review of Nanometer Resolution Position Sensors: Operation and Performance.” Sensors and Actuators a: Physical 190 (nil):106–26. https://doi.org/10.1016/j.sna.2012.10.016.