Capacitive measurement system offers sub-nanometre resolution

Available as a benchtop or 19-inch rack-mounted unit, the new capaNCDT 6500 series supersedes the company's existing capaNCDT 600 series. Modular in design, the system can accept up to eight measuring channels to suit individual customer requirements.

Due to its resolution and flexibility, this system is suitable for high-accuracy R&D applications, test laboratories, quality assurance and academic institutions, as well as semiconductor manufacturing, military, aerospace and defence applications.

Reliable readings

An active-driven, hermetically sealed, triaxial RF cable is used in combination with an active guarded three-electrode sensor. The system is therefore electron leakage-proof, creating a protected and homogeneous measurement field. This means users obtain 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, and also by reducing the time spent recalibrating 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."

Digital data output via Ethernet

With a 24-bit resolution Ethernet port, 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).

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 the analogue signal to a digital Ethernet output internally in the capaNCDT 6500 controller, this problem is eliminated. Data 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 20m between sensor and controller. The sensors operate virtually independently of temperature between -50and +200degC.

Fully compatible with any electrically conductive materials, the capaNCDT 6500 can also measure insulated materials using the system's integrated electronics. In addition, for many applications, earthing of the target material can be difficult or impossible to achieve. However, unlike conventional capacitive measurement systems, the synchronisation of two capaNCDT systems means the target does not require any electrical earthing. The capaNCDT 6500's overall design enables excellent temperature stability of 5ppm/degC for the controller and 11ppm/degC for the sensor.

Applications

A variety of features and characteristics can be measured using capaNCDT sensors, 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.

Micro-Epsilon explains the capaNCDT 6500 systems use a non-contact capacitive measurement principle 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, go to www.micro-epsilon.co.uk/uk-en/Sensors/Capacitive/capaNCDT-6500/.