Product category:
Position, speed and torque measurement
News Release from: Applied Measurements | Subject: LVDTs from Monitran
Edited by the Processingtalk Editorial
Team on 20 March 2007
What are LVDTs, and how do they work?
With the announcement that Applied Measurements is to take over the distribution of the Monitran range of LVDT measurement sensors, here is an explanation of how LVDTs work!
The Linear Variable Differential Transformer (LVDT) is a well-established transducer type which has been used for decades for the accurate measurement of displacement, and within closed loops for the control of positioning systems In its simplest form an LVDT can be thought of as a cylindrical transformer with a central core, a single primary winding and two secondary windings
This article was originally published on Processingtalk on 14 Aug 2008 at 8.00am (UK)
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The primary winding is energised with a constant amplitude AC supply at a frequency of from 1 to 10kHz.
This produces an alternating magnetic field in the centre of the transducer which induces a signal into the secondary windings.
The secondary windings are configured in what's known as a 'push pull' arrangement: the upshot is this: when the core is centred in the LVDT, the excitation transferred from the primary winding is applied equally (in terms of amplitude) to both secondary windings, but in opposite directions: one is received in phase, the other out of phase by 180degrees.
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With the core centred in the LVDT the output voltage from the combined secondary windings is zero.
However, displacement in one direction will result in an AC output in phase with the primary excitation (where the amplitude is in proportion to the displacement) and displacement in the other direction results in an AC output which is out of phase with the primary excitation.
The output signal is actually processed by a phase-sensitive demodulator which is switched at the same frequency as the primary energising supply.
This results in a final output which, after rectification and filtering, gives a DC output (industry standard 4-20mA) proportional to the displacement of the core, in terms of both distance and direction.
For further information, and a diagram of a how an LVDT works, please visit the Applied Measurements website that is dedicated to LVDTs, which is surprisingly www.lvdt.co.uk.
Following the announcement at MAINTEC that Applied Measurements is to take over the UK distribution and sale of Monitran LVDT products, Peter Lewis, Managing Director of Applied Measurements, commented: "There's been an informal understanding between Monitran and Applied Measurements for about six years so it's great that our 'understanding' has now been formalised under the new Monitran management.
Also, with the sale of LVDTs representing about 16% of our own turnover, we're confident this formal arrangement could see us double that figure.
Also to come from this new arrangement, customers should be able to see: shorter delivery times; formalised feedback mechanisms for product queries/feedback; and innovative, higher accuracy products.
Neill Ovenden of Monitran commented: "This is a win-win-win situation really.
Monitran get to focus on product development, Applied Measurements gets to grow the LVDT part of its business and the end-users benefit from the combined experiences of both companies".
Applied Measurements is actively recruiting as part of the expansion plans now in place, to enhance their sales support team. Request a free brochure from Applied Measurements ...
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