1.0 Introduction
A laboratory centrifuge is a piece of equipment generally driven by an electric motor and some older ones usually spun with hand, that puts an object in a rotation around a fixed axis, applying a force perpendicular to the axis. It spun liquid samples at a high speed and thus creates a strong centripetal force causing the denser materials to travel towards the bottom of the centrifuge tube more rapidly that they would under the force of normal gravity. By the same token, lighter objects will tend to move to the top of the tube. The major distinguishing features between centrifuge types are speed and capacity. In a typical laboratory, there exists three different sizes of centrifuges. The smallest are the microfuge centrifuges.
These are made or spinning 1 to 2ml plastic centrifuge tubes at sped up to 12 or 13 thousand rounds per minutes. They have very small, light rotors in them (the rotor is the part of the centrifuge that contains the holes for the sample tubes) which speed up and slow down rapidly. They are convenient for low to medium speed centrifugation of small quantities of materials.
The next common size centrifuge is the large super speed centrifuge that have up to about 20,000 rmp and can take tubes of various sizes, depending on the rotors (the larger the rotor, the slower the maximum speed). Finally, the third size is an ultracentrifuge; speeds up to 70,000 rmp are available on typical modern versions. Its size of tube and maximum speed vary from rotor to rotor.
Before centrifuging, the sample is a tube, a mixture of solutions of differing specific gravities with no clear separation. This makes it impossible to determine how much of each solution is present. After spinning, the samples in a centrifuge, the different solutions in the sample are separated into layers with the heaviest at the bottom of the tube. The quality of each solution can now be readily determined.
Types Of Laboratory Centrifuge
Micro Centrifuge:
They are usually used to spin micro tubes e.g. 1.5/2.0ml, 0.5ml, 0.4ml, and 0.2ml tubes. They have fixed angle rotors (i.e. holes for sample tubes) and have speed up to around 15,00rpm. The rotors can accommodate up to 30 x 1.5ml/2.0ml tubes with the most common being 24 x 1.5/2.0ml tubes rotor.
Refrigerated Microcentrifuge:
They have a cooling system with adjustable temperature in the range — 10oC to +40oC and are usually run at 4oC.
Mini Microcentrifuge:
They usually have a fixed speed (around 600rpm/200xg) and integral rotor for 0.2/2.0ml tubes with adaptors for 0.5ml, 0.4ml and 0.2ml tubes or adaptor to hold 2 times stripes of 8 x 0.2ml tubes. Another model can hold 2 times micro array sides for removing excess liquid.
Benchtop Centrifuges:
They are designed for use on benchtop as opposed to ultra laboratory centrifuges which have to be floor standing. Some benchtop centrifuges are capable of fairly high speed and ref as well as large total sample volumes.
Haematocrit Centrifuge:
They are specially designed for blood sedimentation tests in haematology laboratories, etc and have a rotor specially designed to hold narrow bore micro haemotocrit tubes. The rotor can have a built-in reading for the sedimentation or a separate card can be used to measure the results.
Cytospin Centrifuge:
They are specifically used in cytology laboratory and have special holes for sample tubes and sample holders.
Ultracentrifuges:
They are designed as very high speed (rpm and rcf) centrifuges which have to be floor monitored. They are very expensive and have very expensive holes for sample tubes.
Centrifugal Evaporators:
They are designed to evaporate multiple samples down using a combination of centrifuge/rotor, vacuum pump and solvent trap. The centrifuge chamber can have the option of heating (to speed sample evaporation) and/or Teflon coating (if using samples with aggressive solvents.
1.1 Objectives Of the Study
- To know how centrifuge are being constructed.
- To find out how programmable centrifuge are being used in the laboratory.
- To test the electric power behavior of system or appliances connected to centrifuge.
- To fully understand the automatic means of controlling and sampling the system.
- To discover more details on the fundamental theories of building a programmable centrifuge.
1.2 Scope Of Study
This research is based on the construction of a programmable centrifuge that is used in laboratories. This study is based on how to construct a centrifuge, the effects, maintenance and repair of the centrifuge.
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