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Handbook
November 2011
/
59-UMC0071
/
Issue
01
Mercury
iTC
Page 21
OVERVIEW OF THE iTC
Original Instructions
2.1.1
Temperature sensor circuits
The iTC can interface with a wide variety of temperature sensors. A high-accuracy
measurement circuit amplifies, scales and filters the voltage produced by the sensor.
This conditioned voltage is then passed to a 24-bit analogue to digital converter (ADC).
Some sensors (e.g. resistance sensors) require excitation. For positive temperature
coefficient sensors, this is generated by a high-stability current source. For negative
temperature coefficient sensors, this is provided by a true voltage-source.
The basic iTC can monitor one temperature sensor. Additional sensors can be
monitored by adding daughter boards.
2.1.2
Heater circuits
The demand voltage for the heater is generated by a 16-bit digital to analogue converter
(DAC). This demand is then amplified to a maximum of 80 W output.
The basic iTC can drive one heater. Additional heaters can be driven by adding
daughter boards.
2.1.3
Optional cooling circuit
The system can be configured using an open-loop cooling system. Temperature control
is then performed using the heater only. Improved stability can be obtained if the flow of
cooling fluid is also controlled by the iTC. An optional auxiliary I/O board contains drive
circuitry for a stepper motor. This can drive the opening and closing of a needle-valve,
which can control the flow of a suitable fluid. This function is referred to as gas-control in
the GUI.
2.1.4
Remote interfaces
The iTC contains several interfaces that can be connected to a remote PC:
RS232 / ISOBUS interface.
USB interface.
Ethernet interface.
Optional GPIB (IEEE-488) interface.
The remote PC can send data to the iTC and read data from the iTC. Only one interface
can be active at a time.
2.1.5
Display and touch-screen
The iTC contains a 4.3 inch full-colour LCD display with a touch-screen. The touch
screen is the main input device to the iTC.
The unit contains an ambient-light sensor and can be configured to automatically
change the display brightness to match ambient light conditions.