Multi-channel capacitive measurement system offers extreme resolution

Citation

(2009), "Multi-channel capacitive measurement system offers extreme resolution", Sensor Review, Vol. 29 No. 1. https://doi.org/10.1108/sr.2009.08729aad.004

Multi-channel capacitive measurement system offers extreme resolution

Article Type: New products From: Sensor Review, Volume 29, Issue 1

A non-contact, multi-channel capacitive measurement system has been launched that offers sub-nanometre resolution, unmatched temperature stability and rapid changeover of sensors without any re-calibration required.

The new capaNCDT 6500 Series from Micro-Epsilon supersedes the company’s existing capaNCDT 600 Series and is available as a benchtop or 19 in. rack-mounted unit. Modular in design, the system can accept up to eight measuring channels to suit individual customer requirements.

Owing to its extreme resolution and flexibility, the system is ideal for high-accuracy R&D applications, test laboratories, quality assurance, academic institutions and also semiconductor manufacturing, military, aerospace and defence applications.

The capaNCDT 6500 uses a unique, active-driven, hermetically sealed, triaxial RF cable, in combination with an active guarded three-electrode sensor. The system is therefore electron leakage-proof, creating a protected and homogenous measurement field. This means the user obtains stable, precise, interference-free measurement data.

Chris Jones, Managing Director at Micro-Epsilon UK comments: “What it means for users is that they get an almost perfectly linear measurement system that requires no calibration against any conductive material. If a sensor needs replacing, for example due to mechanical damage, or a different measuring range is required, the user simply disconnects the original sensor and connects the new one in a matter of seconds.”

“Laboratories will see time and cost savings from not having to stock different sensor ranges, but also by reducing the time spent re-calibrating sensors to the target material. The resolution of the capaNCDT 6500 is so high that the user could even sacrifice some of this resolution in order to increase the measuring range. If you halve the resolution, which may still give the user sufficient resolution for the application, the measuring range is doubled,” continues Jones.

The capaNCDT 6500 comes with an Ethernet port with 24-bit resolution, so that measured data can be easily output with no loss of performance (error-free) and then shared with other technicians anywhere in the world, using unique IP addresses and Micro-Epsilon’s special data acquisition software (included as standard).

As Jones explains: “One of the difficulties with very high resolution measurements is the transmitting of data via analogue output channels to the user’s own acquisition system. Quite often, signal noise due to cable interconnects and earthing loops, gives a reduced system performance as this is seen on the output signal as noise. By converting internally in the capaNCDT 6500 controller, the analogue signal to a digital Ethernet output. This problem is eliminated and can then be transmitted anywhere in the world to another IP address.”

Customers can choose from either a version with an integrated preamplifier or one with an external preamplifier, which enables cable lengths of up to 20 m between sensor and controller. The sensors operate virtually independent of temperature and operate between −50 and +200°C.

The capaNCDT 6500 is fully compatible with any electrically conductive materials. Insulated materials can also be measured using the system’s unique integrated electronics. Also, for many applications earthing of the target material can be difficult or impossible to do. Unlike conventional capacitive measurement systems, the unique synchronisation of two capaNCDT systems means the target does not require any electrical earthing.

The overall design of the capaNCDT 6500 enables unmatched temperature stability of 5 ppm/°C for the controller and 11 ppm/°C for the sensor.

capaNCDT sensors can be used to measure a variety of features and characteristics, including vibration; amplitude; clearance; run-out; displacement; distance or position; elongation; deflection; deformation; waviness, and tilt angle. They can also be used for dimensional inspection, parts recognition, tolerance checking and sorting.

The capacitive measurement principle

The non-contact capacitive measurement principle used by the capaNCDT 6500 series is based on the ideal parallel plate capacitor. The two parallel plate electrodes are represented by the sensor and the opposing target. If an AC current with constant frequency flows through the sensor capacitor, the amplitude of the AC voltage on the sensor is proportional to the distance between the capacitor electrodes; and adjustable compensating voltage is simultaneously generated in the amplifier electronics. After demodulation of both AC voltages, the difference is amplified and output as an analogue signal.

For more information on Micro-Epsilon’s new range of multi-channel capacitive sensors, please call the sales department on Tel.: 0151 355 6070 or E-mail: info@micro-epsilon.co.uk