Test & measurement
repair cards long after the five years have passed. That i very reassuring as long-term experiments can often be confronted with a large effort to redevelop a system because the original hardware at the heart of it is no longer available.” Because of the large quantities of data
is very sensitive to correlated signals and crosstalk between channels including anything picked up along the way from the optical sensors through to the computer that the digitiser cards are mounted in. To put it into perspective, these Spectrum cards enable us to precisely measure fluctuations of the light intensity on nanosecond time scales giving unprecedented sensitivity that is around ten times better than that achieved in the 1970s with the Narrabri interferometer.” “The other important factor in choosing
Spectrum digitiser cards is their excellent reputation for reliability. The cards are located by the two telescopes that are high up in the mountains on the island of La Palma, one of Spain’s Canary Islands, so it is not a simple matter to swap in a new card if there is an issue. Plus, there is the cost of instrument downtime and lost observation time. The fact that Spectrum provides a five-year warranty shows their faith in the high quality and reliability of their cards which was supported when we checked with other users in the scientific community. Lastly, Spectrum assured us that they can
being handled, the system uses Spectrum's SCAPP software (Spectrum’s CUDA Access for Parallel Processing). This is a way of sending all the collected data from the digitiser not to the CPU of a PC with 8 or 16 processor cores, but to an NVIDA PC graphic card because the GPU graphic processor has up to 5000 cores giving much faster data processing. This enables recordings to be run in high resolution with 500 Megasamples per second.
inductive sensors manage web tension
A
manufacturer of textile handling machines trusts
the speed, precision and reliability of Contrinex’s long-range analogue inductive sensors to measure the small changes in the position of a ‘dancer’ roller or ‘follower’, which follows the fabric web’s position and so indicates the web’s tension. The sensor’s precision measurement is fed into a tension control system, which in turn provides continuous feedback to a variable speed drive. As the textile web is unwound and fed into the
machine, the control system must compensate for minor changes in tension. These can be due to variations in the properties of the fabric and from within the machine itself, such as slight deformation of the rollers, alignment issues, and the requirement to enable acceleration/ deceleration to make speed changes. A web tension control system registers these
The diameter of a distant star is measured
by digitising the variations in the light received from a star. The cross correlation is then computed and averaged during observation to determine its variation as a function of the separation between telescopes. The geometry changes as the star moves across the sky. Measuring a shape requires observations along multiple axes.
Spectrum Instrumentation
www.spectrum-instrumentation.com
tension changes via a dancer roller, which rises and falls constantly in small increments (‘dancing’). Encoder or precision potentiometers are typically used by the customer to measure the ‘dancer’ roller’s position, providing a signal to the machine controller, which adjusts drive speed/braking accordingly. Encoders and potentiometers have a moving
shaft coupled to the pivoting dancer arm of the dancer system and are therefore subject to wear and tear on delicate bearing surfaces and well as limitations in the service life of the encoders and potentiometers in a dusty or fluffy environment. To avoid these problems the customer was looking for a non-contact solution. Contrinex analogue inductive sensors from
max Planck institute uses spectrum’s digitiser cards to measure diameters of distant stars
Instrumentation Monthly January 2022
their Extra Distance 509 Series family, available from PLUS Automation, provided the perfect solution for this application and the dusty environment. Their Condist oscillator technology ensures excellent temperature stability and repeat accuracy which is required for precision measurement at longer operating distances (up to 40mm) to a resolution in the µm range. Their speed, resolution and continuous non-
digitised output is particularly suitable for fast precise measurement of the constantly ‘dancing’ roll in this feedback control system. The use of an analogue inductive sensor
requires no mechanical contact but merely an elliptical metal target or direct view of the moving dancer arm. It is then possible to interface the sensor output directly to a controller, with several switch points included in a single device. This greatly simplifies installation, while the problems of wear and tear associated with mechanical contact are also avoided.
PLUS Automation
plusautomation.co.uk 35
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