MercuryiTC
©2014 Oxford Instruments Omicron NanoScience. All rights reserved.
Page 150
• Manual PID
The PID parameters are entered directly on the Control Loop Configuration page (see
section 4.3 for heater control and 4.9 for gas control). The same parameters are used for the
entire temperature range over which the control loop operates.
• Auto PID
The PID parameters are obtained from a PID table (see section 4.5.2). This method allows
the PID parameters to vary with the controlled temperature.
The image below shows an example PID table containing two rows. The values shown in this
table are not from a real system.
14.3 Theory of gas-flow control
14.3.1 Overview of gas control
The iTC can drive a motorised needle valve which controls the flow of a cooling gas. Controlling
the gas-flow regulates the cooling power, which provides control of the sample temperature.
There are two alternative algorithms that may be selected for automatic control:
• Variable Temperature Insert (VTI)
This algorithm is used if the coolant is supplied from a local bath.
• Siphon
This algorithm is used if the coolant is supplied from a dewar.
PID values
used between
5 – 10K
PID values
used between
10 - 25K
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