MercuryiTC
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both the temperature error and the heater voltage error are zero, at which point the valve
opening remains constant.
14.3.4 Heater target tables
The target heater voltage is contained in the Heater Target Table (HTT). This table contains a
set of target heater voltage values, each corresponding to a specified temperature range. The
target voltage value in the table is scaled to the maximum heater output voltage (see section
4.3), and is multiplied by the gas flow scaling factor (see section 4.9.2), to obtain the final target
heater voltage. The user can select which Heater Target Table to use, but can not edit a Heater
Target Table. Contact Oxford Instruments Omicron NanoScience to obtain a Heater Target
Table to suit your application.
14.3.5 Siphon algorithm
This algorithm is used when the coolant is supplied from a dewar. The algorithm controls in the
same way as the VTI algorithm described above, with the following exceptions:
1 If the present temperature is more than X degrees above the setpoint, the gas flow valve
opens fully to provide fast cooling.
(Where X is 20% of the setpoint or 20 K, whichever is the greater).
2 If the present temperature is rising, when it reaches 80% of the setpoint the gas flow
changes to 50%. The automatic algorithm then starts controlling from this point.
3 If the present temperature is less than 95% of the setpoint, the gas control valve remains at
its present value. When the temperature rises to within 95% of the setpoint, the gas control
valve controls automatically again.
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