Method and device for monitoring the rotational speed of an element

A device for monitoring a rotational speed of an element and detecting when the rotational speed of the element exceeds a predetermined rotational speed, comprising:

• a clock generator which generates a clock signal with a defined frequency,
• a revolution detector which senses rotation of the element by a predetermined fraction or multiple of one revolution;
• a binary counter adapted to count a number of cycles of the clock signal during which the element rotates by the predetermined fraction or multiple of one revolution;
• a comparator adapted to compare the counted number of cycles with a predetermined counting value;
• and
• a results memory configured to store that the rotational speed of the element has exceeded the predetermined rotational speed, the results memory having an input for a control signal indicating that the element has come to a standstill or has reached a peripheral speed of less than 3 m/s,
• wherein the control signal causes the results memory to be deleted,
• wherein exceeding of the predetermined rotational speed is detected by the counted number of cycles falling below the predetermined counting value, and
• wherein the device reduces the rotational speed of the element when the counted number of cycles falls below the predetermined counting value.

A method for preventing excessive rotational speed of a rotor within a centrifuge, comprising:

• generating a clock signal with a defined frequency;
• counting a number of cycles of the clock signal within a period of time during which the rotor rotates by a predetermined fraction or multiple of one revolution;
• comparing the counted number of cycles with a predetermined counter value;
• determining that the rotational speed of the rotor exceeds the predetermined rotational speed when the counted number of cycles falls below the predetermined counter value;
• storing, in a results memory, that the rotational speed of the rotor has exceeded the predetermined rotational speed;
• transmitting a control signal from the results memory to a motor controller while the results memory stores that the rotor has exceeded the predetermined rotational speed;
• reducing the speed of the rotor to a standstill in response to the control signal;
• and
• deleting the results memory by a control signal indicating that a cover of the centrifuge has been opened.