Motion control brings performance benefits for microbial air sampler

Setting it even further apart from competitive air samplers, the range also offers features based upon motion control technology supplied and supported by Mclennan, the motion systems supplier.

Known as a ´slit-to-agar´ air sampler, the device draws air at high speeds through a narrow inlet slit whereupon particles, including microbes, impact and adhere to the agar surface of a petri dish that is analysed in another process.

By introducing precision rotation of the dish into the design, Pinpoint have ensured that the air is always impacted onto a fresh area of agar to dramatically reduce the probability of ´twin impingement´ - a phenomena where two microbes land at the same point and appear as a single colony when incubated, causing uncertain results. By controlling the rotation speed and angular rotation factors through a stepper motor driven miniature gearbox, the sample is precisely calibrated and can be consistently compared over a series of similar runs from a few minutes to several hours.

Furthermore, the ImpactAir microbial air sampler is the first of its kind to employ precision sensors and a miniature stepper motor driven linear actuator to automatically adjust the distance between the air inlet and the agar surface - a critical factor that can vary significantly due to the agar thickness.

The introduction of motion control has resulted in the ImpactAir´s ability to ensure a consistent microbial air sampling performance factor that has been independently verified by Public Health England (PHE) following physical and biological validation.

Mclennan worked closely with designers at Pinpoint Scientific to develop the two motion axes used for the ImpactAir. The compact design, laboratory quality build of the device, and the need for the highest reliability led to a competitively priced but high quality solution based on products with a proven performance for medical equipment applications.

The rotation axis uses a P5 series high precision instrument ovoid type gearbox with stepper drive providing a 120,000 step/rev for a final angular positioning resolution of 0.003°. The linear actuator is an integral solution from Mclennan´s distribution partners Portescap.

The vertically mounted 26DBM-K can-stack linear actuator includes a hollow-shaft stepper motor fitted with a precision leadscrew that drives the petri dish mechanics via a preloaded nut arrangement. With a precision leadscrew and its 48 step/rev motor resolution a linear resolution of 25µ is achieved, which is well within the accuracy tolerance for the machine. The stepper motor drive and motion controls are integrated into the device control system which also manages the airflow and other machine parameters through a choice of integrated touchscreen or external interfaces.