J-KEM Scientific Gemini-230, Руководство пользователя

Страница: 18 / 46

18
controller to stay at the setpoint for the entered time and then turn power to the heater off after the time
expires.
Important Points to Know
1. While the Ramp-to-Setpoint feature is activated, the display alternates between the current reaction
temperature and the word “
SPr
” to indicate that a “SetPoint Ramp” is active.
2. If this controller is equipped with a digital 100-hour timer, the digital timer and the Ramp-to-Setpoint
feature are completely independent of each other. For example, if the digital timer is set to turn heating
OFF after 5 hours, heating
is turned off even if a ramp step is in progress. Likewise, if a Soak time
turns heating off after 3 hours and the digital timer is set to turn heating off after 10 hours, the digital
timer has no effect since the expired Soak time already has turned heating off.
3. Once the Ramp-to-Setpoint feature is activated in programming mode, it remains on until it’s
deactivated in programming mode. The Ramp-to-Setpoint feature remains activated even when power
is turned off, and then turned back on.
4. Setting a ramp rate in the digital controller does not guarantee that the reaction itself will ramp at the
entered value, since the rate of heating is dependent on the power of the heater. Setting a ramp rate in
the controller only guarantees that the controller’s setpoint will be changed at the entered rate. For the
reaction temperature to increase temperature at the specified rate, the heater must have sufficient power
to heat at the entered rate. This is a critically important point, the user must understand that the
electronic setpoint in the controller will ramp at the entered rate, but the controller cannot
force a heater
to heat a reaction faster than it’s capable of doing. For example, see the plots below.
Plot 1 – This plot uses a heating mantle to ramp temperature in reaction from 20 to 80C in 60 minutes. The
reaction temperature closely matches the setpoint of the controller because heating mantles have enough
power to heat a typical reaction at the modest heating rate of 1 degree per minute.
Plot 2 – In this example, the ramp rate is set to 600 C/ hour, or 10 C per minute. The controller ramps the
setpoint at the requested rate, but the reaction temperature does not match the ramp, because the heater does
not have enough power to heat the reaction as such a high rate.
Every time the reaction temperature does
not match the entered ramp rate, it’s because the heater has insufficient power to heat at the requested rate.
The only solution to this situation is 1) use a more powerful heater, or 2) lower the ramp rate to a value that
does not exceed the heaters maximum heating rate. The controller has no influence over a heater that has
insufficient power to heat at the entered ramp rate.
Plot 1 Plot 2
0 0.2 0.4 0.6 0.8 1.0
1.2
Hours
Controller Setpoint
Reaction Temperature
0
40
80
0
0.2 0.4
0.6 0.8 1.0
1.2
Hours
Controller Setpoint
Reaction Temperature
0
100
200
300