While true in many facets of instrument support, there is one other tool which lab support techs will find invaluable – the digital tachometer. A more precise name would be a strobe tachometer, which neatly describes the basic theory of operation…a strobe light which is used to monitor the rotational speed of the rotor.
The LW Scientific Hand-Held tachometer can be found at a variety of web stores for under $200.
This device is easy to use and comes with reflective tape targets that you can place on the rotor arm. Simply point the tach at the rotor in the general area of the target and hold it steady…after a few seconds you will see a reading that while changing, stays within the commanded speed. This device can monitor speeds from 20-50,000 RPM which makes it ideal for most lab centrifuges and has a range of 50-400mm. It’s accurate to +/- 20 RPM, so obviously you would want to be a bit skeptical at the low end range…
Interestingly, most separation assays call for acceleration of the sample not the rotational speed. From a repair or assay integrity perspective, checking RPM’s will suffice as a general method to determine that the instrument is performing as specified by the manufacturer. For those who are more curious, there is a great Wiki with more info.
Some centrifuge brands have sight glass windows that allow the digital tach to observe rotor speed while the unit is running…others do not. Now comes the inevitable caution…caution! (notice I even used an exclamation point). Seriously, most centrifuges are capable of causing great physical harm due to their extremely high speeds. Safety interlocks that prevent internal access while spinning are there for a reason. While a trained tech can defeat such locks, it is not advisable for a novice. If you any doubts click this image to learn how dangerous high-speed centrifuges can be…
Manufacturer or third-party FSE’s re-calibrate the speed of a centrifuge by adjusting one or more potentiometers on the control board. Initial speed setting is typically done without a rotor in the unit.
One last caution kids…speed kills. Let’s be careful out there.