Temperature control can be crucial in the research lab when establishing procedures aimed at developing new products and processes. Benchtop hotplate magnetic stirrers allow researchers to exercise close control over sample temperature during their experiments. A magnetic stirrer temperature probe dramatically increases temperature measurement accuracy and provides additional benefits.
A hotplate magnetic stirrer allows researchers, as you might imagine, to heat samples during the stirring cycles. Temperatures can be controlled to as high as 450?C (842?F) in CAT Scientific hotplate magnetic stirrers.
When programming processing speed and processing time, researchers also program processing temperature in hotplate magnetic stirrers. The point being, this is the hotplate temperature, not the sample temperature. The difference between plate temperature and sample temperature may be important. Also important is sample evaporation or loss due to beaker failure when samples are at such high temperatures.
Benefits of a Magnetic Stirrer Temperature Probe
Hotplate magnetic stirrers such as the CAT MCS78 provide two means of temperature control. Optimal performance in terms of temperature control and overall operation is provided when an external temperature probe is used.
Designated as the Pt100 probe, these are described as a platinum resistance thermometer (PRT) or a resistance temperature detector (RTD). Because of their accuracy and repeatability they are replacing thermocouples as a means of gauging temperature.
The principle of operation is to measure the resistance of a platinum element over the operating temperature range of the magnetic stirrer. Wide temperature ranges such as the 440?C upper limit of the CAT MCS78 model magnetic mixer can easily be accommodated with the Pt100 probe.
While temperature probes can be simply inserted in the mixing vessel a better option is affixing them to a clamp or support rod so the tip is not in contact with the bottom of the sample flask. This assures that the probe will not be nudged by the spinning stirring magnet or get an incorrect reading because of its proximity to the hotplate.
How to Operate Magnetic Stirrers with Pt100 Temperature Probes
Full operational instructions are provided with each CAT Scientific magnetic stirrer. But in brief, here’s how to set things up using our MCS78 model:
Connect the external Pt100 probe to the socket marked Pt100 at the rear of the unit.
Put the Pt100 probe into the vessel on the hotplate and immerse it at least 2cm in the liquid
Press power on/off to switch the unit on
Press the probe temperature button to set the desired probe temperature (ProbeSet) with the up/down keys
Press the plate temperature button to set the maximum allowed hotplate temperature (PlateLim) for the heating process. Note: This temperature should always be set as high as possible to allow the control algorithms to freely select the optimum hotplate temperature. The PlateLim temperature must always be set at least 10%-20% above the programmed probe-temperature. Otherwise the liquid cannot reach the programmed temperature or the heat up time would become extremely long.
Press plate on/off to activate the hotplate (green control LED must be on)
Press motor on/off to switch on the stirring motor
The MCS78 magnetic mixer will automatically select the fastest optimum hotplate temperature to reach the desired liquid temperature.
Safety Features
Another benefit of using temperature probes is their contribution to the safe operation of CAT magnetic stirrers by initiating shutdown procedures in the event that
The Pt100 tip is not immersed in liquid
If there is a discrepancy between the probe temperature and the hotplate
If there is no increase in liquid temperature over a certain time but the hotplate temperature is rising
If the probe is accidentally disconnected from the back of the unit