Exercise S
133
Log the temperature for 10 minutes.
Increase the PSV setting by a further 20%, and open the drain valve more to
maintain the fluid level within the vessel.
Continue to log the temperature for another 10 minutes, and then select the
icon
to finish data logging.
Set the PSV back to its original setting and close the drain valve.
Temperature Set Point
Investigate the effect of changing the temperature at which the on/off heater switch
operates:
Select the
icon to create a new results sheet.
In the software, alter the temperature set point to 40°C.
Select the
icon to begin data logging.
Log the temperature for 10 minutes, and then select the
icon to finish data
logging.
Select the
icon to create a new results sheet.
Repeat the procedure, altering the set point and logging the change in temperature
until the oscillations reach stable values. Suggested values for the temperature set
point value are 50, 60 and 70°C. Remember to create a new results sheet for each
set of data. Note that the heater circuit includes a safety cut-out that will shut off
power to the heater if the temperature of the process vessel reaches approximately
80°C. Set point values should therefore be kept below this temperature.
Results
For easy identification or results, it is suggested that each results sheet is renamed
with a descriptive title (e.g. ‘Flow Rate’, ‘Set Point’, etc.). The entire workbook should
be saved with a suitable filename for future reference (e.g. PCT40 Exercise S).
Each set of data should be plotted on a graph of temperature T1 against time.
Make a comparison of each variation in the experimental conditions against the
graph of the initial set of results, noting the difference in response.
Give examples of industrial control situations for which a simple on/off controller
would be suitable.
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