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Vibration sensor NVA

Vibration sensor NVA
12Pages

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MEMS vibration sensor NVA 65 with analogue and CANopen interface Design The sensor system is intended as a component for use e.g. in wind power plants to measure and evaluate vibrations in the mast head. Registration of dynamic accelerations by means of MEMS sensors (Micro-Electro-Mechanical System) with subsequent digitisation by a controller. The device consists of an acceleration sensors, a controller unit and three types of output interface. Data output is carried out via two analogue interfaces with 4 ... 20 mA plus CANopen and via 4 relay contacts (currently 1 error relay contact). The NVA is parameterised via the CANopen interface. This is not galvanically separated. The sensor is equipped with a filter circuit to protect against fast transients and surge voltages of up to 2 kV in the supply. The protection types are IP 69K (housing) and IP 67 (connector/socket). With its good vibration and shock values, the sensor is suitable for use in areas with rough environmental conditions. The vibration sensor is equipped with a stable aluminium housing (optionally stainless steel). Elongated holes are available for mechanical alignment (up to approx. ± 7.5°). Electrical connection is carried out using two connectors or two cables. Function MEMS sensors are integrated circuits which are manufactured in silicon bulk micromechanics technology. Double capacities are formed with the aid of these micromechanical structures. If these structures are deflected in the case of accelerations, this leads to capacity changes which are registered using measuring technology and further processed. The sensors measure precisely, have a long service life and are very robust. ■ Contactless, wear-free sensor system in MEMS technology ■ Number of measurement axes: 2 ■ Frequency range: 0.1 ... 60 Hz Option: 0.1 ... 100 Hz ■ Measuring range: ± 2 g ■ Interfaces: analogue, CANopen, relays ■ Resolution: 4096 digits / g ■ Output: Momentary value RMS value Peak value ■ Operating temperature range: - 40 °C to + 85 °C ■ Parameterisable via CANopen After determining the steady component and scaling, the measured values supplied by the acceleration sensor are made available to the six filter units. The steady component arises as a result of installation which is not precisely horizontal, with the result that part of the earth's gravitational field would also be measured. The offset which occurs in the measured vibration value curve (zero point shift) due to the steady component is determined by means of calculation (distribution of the positive and negative measured values around the zero point) and is subtracted. The pure alternating component is output within a matter of seconds. This calculation takes place continually. The filter units can be individually programmed by the customer as regards their sampling frequency, whilst their filter characteristics can be programmed in the factory. Each filter unit additionally has two outputs (flags) for alarm and warning. If the amount of a filter output's measured value exceeds the set limit value the output is activated. The limit values for triggering the outputs can also be programmed by the customer. The warning and alarm outputs can be connected to the four relay outputs via a matrix which can be programmed by the customer. Several filter outputs may additionally be connected to the relay outputs by means of an OR link. The analogue outputs are firmly connected to filters 1 and 2. The outputs output the filtered signed signal supplied by the acceleration sensor. The quiescent level of the 4 ... 20 mA interface is 12 mA with an acceleration of 0 m/s2 or 0 g. Amplifier setting is individually possible for each channel via the CANopen interface. The CANopen interface can be used to set the parameters and call up the 6 filters' outputs. With the exception of the filter characteristics, all parameters are programmable. TWK-ELEKTRONIK GmbH Heinrichstrasse 85 info@twk.de www.twk.de

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MEMS vibration sensor NVA 65 Description General information The vibration sensor measures on two axes in a frequency spectrum from 0.1 to 60 Hz (Option: 0.1 to 100 Hz). This spectrum can be subdivided into a maximum of 6 frequency ranges. The frequency ranges are set in the factory. They can also be subsequently shifted by the customer by means of CANopen objects. All acceleration values acting within the relevant frequency window are registered and are output firstly as an analogue value (4 ... 20 mA, max. two outputs possible) and secondly as a digital value via CANopen. The acceleration...

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MEMS vibration sensor NVA 65 Examples for fiter output Fig. 1: Example band pass filter fgu = 0.8Hz, fgo = 2.5 Hz Fig. 2: Example of a low pass filter fgo = 23 Hz Diagram for analogue output I0(a) I [mA] Output: signed Output: absolute value  x, momentary value  y, momentary value  x, RMS value  y, RMS value  x, Peak value  y, Peak value  √(x²+y²), RMS value  √(x²+y²), Peak value  √(x²+y²), momentary value

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Parameters programmable via CANopen interface ■ Measuring axis: x or y or V(x2+y2) separately for each filter 1 - 6 ■ Sampling frequency (120 ... 800 Hz). Can be set separately for each frequency band. ■ Filter frequency range (by changing the sampling frequency)* ■ Signal type at filter output 1 - 6: momentary value, RMS mean value, peak value or degressive peak value ■ Averaging time for signal type 'RMS' ■ Decrease time for signal type 'Peak' ■ Amplification for analogue outputs 4 ... 20 mA ■ Acceleration limit values (limit) for relay warning function ■ Acceleration limit values (limit)...

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MEMS vibration sensor NVA 65 Optional functions (subject to consultation with TWK)         System calibration for higher accuracy Programmable steady component in the output signal (measured vibration value curve zero point shift) Up to 8 relays Transistors instead of relays Further filters Evaluation procedures (Datalogging, log functions with programmable triggering, statistics, protocol functions) Safety design for safety applications Other customer variants CANopen technical data CANopen communication profile  Full CAN part A (11-bit) CANopen 301 V 4.1 (no galvanic bus...

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Vibration sensor NVA 12Pages

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Vibration sensor NVA
12Pages