Computer Controlled Magnetic Stirring | CAT Scientific

How to Use Computer Controlled Hotplate Magnetic Stirrers

A computer controlled hotplate magnetic stirrer is designed to accomplish a variety of processing tasks, generally originating in the R&D facility.  Its application can migrate to use in pilot plants and even to small-scale  production facilities.  A goal of using computer controlled hotplate magnetic stirrers is developing optimum processing procedures.

This post provides

  • a description of magnetic stirrers
  • advantages of hotplate magnetic stirrers
  • enhancements supporting computerized hotplate stirrer applications
  • definitions of key terminology

What is a Magnetic Stirrer?

First, there are two commonly used devices to perform stirring operations in labs and pilot plants.  One is the overhead stirrer, where stirring is accomplished by motor-driven paddles available in several configurations.  A panel allows researchers to control the unit’s operation.

Magnetic stirrers, as you might surmise, use small magnets to do the stirring.  The  magnets are called fleas and are placed in sample beakers or flasks.  The container and its contents are placed on the magnetic stirrer platform, under which is a rotating magnet.

When activated the rotating magnet causes the flea to rotate in the sample container thus performing the stirring function.  Operators control stirring speed and time.

What is the Advantage of a Hotplate Magnetic Stirrer?

Hotplate magnetic stirrers for flat or round-bottom flasks provide the ability to determine optimum temperatures under which to conduct R&D, pilot plant or production line processing.

They are very popular in biological and pharmaceutical labs because they allow researchers to experiment with a wide range of mixing and stirring options under different temperatures.

Computer Controlled Hotplate Magnetic Stirrers

CAT Scientific offers a variety of hotplate magnetic stirrers that can function individually or in tandem with remote operating capability provided by programmable logic controllers* and/or manufacturing execution systems **.  Several options are available for interconnection such as RS485 or RS232 interfaces to specialized vendor software***.

Accommodating Variables in Magnetic Stirring

CAT Scientific’s hotplate magnetic stirrers operate over a wide range of stirring speeds and temperatures.  Variations in both of these parameters are often required.  These can include

  • programmed on-off cycles
  • variations in stirring speed
  • programming mixing cycles from minutes to hours
  • rpm changes for long or short durations
  • temperature changes of long or short duration.

Automated lines such as described introduce other performance requirements, namely reliability because the units are not monitored 100% of the time by personnel.

Temperature sensors such as the CAT PT100 platinum temperature probe play an important part in equipment monitoring and can initiate a unit shutdown in the event of equipment malfunction or temperature excursions.

Special Magnetic Stirrer Requirements Accommodated

For example, processes may call for introducing dry chemicals into the solution during mixing operations.

Because there is no physical connection between the free container magnet (the flea) and the motor-powered mixer magnet two points should be kept in mind.

  1. Chemicals should be introduced slowly to avoid clumping at the bottom of the container.  This could cause the rotating magnet to go off center.
  2. A stronger rotating magnet can be specified in the base of the mixer to keep the rotating magnet on center.  Stronger motor-driven magnets can also be specified if containers have a thick walls and bottoms.

This point is particularly important when operations are controlled remotely by PLC or MES systems as an off-center stir bar may not be immediately noted by monitoring personnel.

In conclusion, CAT Scientific offers a range of hotplate magnetic stirrers and automation options.  If you don’t see the magnetic stirrer you want on our website simply ask us for a recommendation.  We’re glad to help you solve challenges in your research or production facility.

* A programmable logic controller, PLC, is a digital computer used for automation of typically industrial electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many machines, in many industries.

** A manufacturing execution system (MES) is an information system that connects, monitors and controls complex manufacturing systems and data flows on the factory floor. The main goal of an MES is to ensure effective execution of the manufacturing operations and improve production output.

***An example of CAT Scientific software is described in our article, ‘How Programming Software Enhances Hotplate Magnetic Stirrer Functionality’.

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