If the displacement is kept within a specified range, the output voltage varies linearly with displacement. The AD598 can drive an LVDT at the end of 300 feet of cable, since the circuit is not affected by phase shifts or absolute signal magnitudes. Finally, the input and output circuits are electrically isolated from one another so that excitation ground and signal ground are totally independent from one another. By continuing you agree to the use of cookies. LVDTs are offered with different armatures, stroke lengths, with or without built-in electronics, and manufactured for various temperature ranges. Rotational magnetic encoders may have up to 10 bit resolution. The position output range of VOUT is ± 11 V for a 6 mA load, and it can drive up to 1,000 feet of cable. LVDTs are a type of two-part inductive sensor in which a ferromagnetic armature moves within an outer transformer consisting of one primary and two secondary coils. Because there is no physical contact across the sensing element, there is no wear in the sensing element. 15(a). A wide variety of measurement ranges are available in different LVDTs, typically from ±100 μm to ±25 cm. LVDT is used to calculate displacement and works on … Inductive transducers measure static and dynamic displacements. It transfers the electrical energy from one circuit to another by inducing a change in voltage or current. The AD698 can also be used with a half-bridge (similar to an auto-transformer) LVDT as shown in Figure 3-6. The sealed LVDT, for example, is made of stainless steel and can be placed in corrosive liquids or gases. In its simplest form, the LVDT consists of a cylindrical, insulating, nonmagnetic form that has a primary coil in the midsegment and a secondary coil symmetrically wound in the two end segments, as depicted schematically in Fig. Half-bridge LVDT configuration. Since the two secondary coils are connected in series opposition, so that the potentials induced in the two secondary coil segments oppose each other, it is seen that the net induced voltage is zero when the core is centered between the two secondary winding segments. It is an electro-mechanical device designed to produce an AC voltage output proportional to the relative displacement of the transformer and the ferromagnetic core. The strength of the LVDT sensor's principle is that there is no electrical contact across the transducer position sensing element which for the user of the sensor means clean data, infinite resolution and a very long life. The basic circuit consists of an LC oscillator, which is “killed” by losses due to the eddy currents. A transducer is a device that converts energy from one form to another. Ordering information: application, length of rod, and linear range. Linear range: to be specified (available 25 mm to 500 mm). The industry-standard AD598 LVDT signal conditioner shown in Figure 3-4 (simplified form) performs all required LVDT signal processing. This armature type is specialized for longer measurement ranges of – ±0.5” to ±18.5”. When the core is properly supported, there is no friction between the sensing elements. Drive capability is 30 mARMS. The main advantage of the LVDT transducer over other types of displacement transducer is the high degree of robustness. G.E. The input is applied to a V/I converter which in turn drives an analog multiplier. While the core remains within the operating range of the LVDT, the amount of output voltage is linearly related to the displacement of the core (Fraden, 2010). They are. These circuits are well-understood by integrated circuit (IC) designers and are easy to implement on modern bipolar processes. ± 100 μm to ±25 cm a single external resistor sets the excitation... 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