High-precision speed measurement

Pharmaceutical companies analyse product batches at regular intervals to ensure the high quality of their medicines. MEGATRON encoders record the speed in the drives of the test equipment, thus enabling standardized analysis procedures.

A well-known manufacturer of laboratory equipment has been using MEGATRON's SPTSM series of optoelectronic incremental encoders to drive its tablet testers for more than two decades. In the dissolution testers, so-called paddles rotate in a glass container filled with a liquid medium. The pH of the liquid is adapted to the environment found in the human digestive tract. The paddles keep the medium in motion until all the active ingredients in the tablet have been released.

The MEGATRON encoders continuously record the speed of the electric motor and monitor the stirring process of the unit with 360 pulses/360°. This ensures that the stirrer always operates at the same speed and that test results are comparable. In terms of speed measurement accuracy, the SPTSM far exceeds the requirements of the test equipment manufacturer: the maximum deviation in speed measurement should be ±2 per cent. However, the encoder measures the speed of the stirrer drive with a deviation of only 0.2%.

SPTSM encoders are based on the principle of optoelectronic scanning, i.e. they operate without contact and are therefore virtually wear-free. Another feature of the encoders is their insensitivity to magnetic fields, which are common in laboratories and industrial plants. The SPTSM is a kit encoder: it does not have its own shaft but is mounted on the shaft of the application (shaft diameter from 4 mm to 8 mm). Thanks to this special design, the encoder does not require its own bearing, which could wear out. The SPTSM is also available with an integrated shaft (6 mm/6.35 mm) under the designation SPM.

MEGATRON has adapted the SPTSM for use on the tablet testers: The contact pins of the optical encoder module are soldered to the wires of the connection cable at the factory. This ensures that the cables are firmly attached and prevents incorrect installation on the tester drive. Customized service is one of MEGATRON's standard services: the company adapts its products to the respective application, even for relatively small quantities. For example, customized pulse counts, inch shaft diameters, a through-hole in the housing cover or cable assemblies are all possible.