difference CAP - SG
What are the differences with closed loop systems between capacitive feedback sensor and strain gauge feedback sensor?
What are the differences between closed loop systems with a capacitive feedback sensor and those with a strain gauge feedback sensor?
Piezo systems with capacitive sensors have better resolution (sensor resolution 1 nm), non-linearity (typ. 0.05%), and repeatability. Capacitive systems are the best choice for applications that require good long time stability. Normally these sensors are arranged in the actuator between the fixed-point and the drive side. Thus, they register the whole mechanical assembly and control the position with high precision.
Strain gauges provide a resolution of up to 35 nm. Their advantages include a small size and large bandwidth of up to 5 kHz. They are a good option for applications with resolutions above 35 nm. A disadvantage is the local configuration of the measurement bridges that do not allow all drift effects to be measured. This reduces their capability to provide high of a long term stability.
CAP - advantages
- high measurement accuracy, optimal for long time applications
- good values regarding non-linearity, repeatability, and resolution
- cross motion is compensated for e.g. at XY systems
CAP - disadvantages
- often the actuators have a bigger footprint
- bandwidth max. of 1 kHz
- more expensive
DMS - advantages
- very compact size
- big bandwidth of up to 5 kHz
- more cost effective than the CAP
DMS - disadvantages
- no high long term stability
- resolution not better than 35 nm
- cross motion is not compensated for