Electronics Weekly
The module works with pairs of eddy current coils, connected by flying leads, positioned on the mirror assembly so that the parts of the mirror move away from one coil while approaching the other.
The new module, KD-5100+, can work with two pairs of sensors, for example positioned in a diamond pattern as two differential pairs behind the flat back of a mirror that rocks around both X and Y axis in a fully steerable system.
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KD-5100+ features a stable design, small size and low power consumption, making it ideal for laser communications satellites and ground stations, image stabilisation systems, and directed energy systems for ground, shipboard and airborne applications,” said the company. It “is an ideal solution for meeting SWaP-C requirements. It is manufactured to Mil-PRF-38534 Class H, with MIL-SPEC components used throughout the electronics”.
There is a choice of coils: Model 15N offers ±0.9mm movement range, while Model 20N offers ±1.9mm.
These intended to work with moving aluminium parts, and some other non-ferrous metals, but not ferromagnetic targets such as iron or nickel.
Long term drift in measurements once the device is calibrated is typically “less than 2 microinches per month”, according to Kaman – which equates to <50μm.
Within the unit, the coils are connected in opposite legs of a balanced bridge, energised with ac current.
When the target is equidistant to the coils, the bridge is balanced, and the progressively un-balanced as movement occurs. Any resulting bridge output is amplified and demodulated to produce a linear analogue signal proportional to the target’s position.
The output is differential, and bipolar to indicate both magnitude and direction of distance difference. Output scaling factor is typically 40mV/1μm, and low-pass filtering can be used to trade bandwidth for noise to improve accuracy.
The unit measures ~51 x 56 x 19mm and consumes 70mA from ±15Vdc supplies.
Operation is over -20 to +60°C, while the coils work over -55 to +105°C – and there is a 4K cryogenic version of the 20N.
Kaman Precision Products is based in Connecticut.
Find the KD-5100+ sensor’s web page here
