VICI ITC - Manual (Page 3)

1.
INTRODUCTION AND GENERAL DESCRIPTION
The Instrumentation Temperature Controller (ITC) is an isothermal temperature
controller intended for broad spectrum usage in thermal systems common to
modern analytical instrumentation. The instrument is designed to be a flexible
building block with which the user can configure a thermal system to suit particular
requirements. Although the controller is only a single element in such a system,
its flexibility and performance ultimately determine the stability, reproducibility, and
accuracy of the entire system.
Inasmuch as we do not attempt to present a portfolio of specific applications, this
manual is more general than specific. Instead, we are attempting to strike a spark
of intuitive understanding and interest for how the ITC functions. The ITC’s func-
tion and relationship to thermal systems are the most valuable notions transmitted
by this manual. Just as there is no application manual for vice-grip pliers, there is
not an application manual for the ITC. Both are basic, extremely useful devices,
whose real worth is determined by the user.
1.1 Standard Features
1.11 Thermocouple Sensors
The ITC utilizes thermocouple sensors fabricated from ordinary thermocouple wire.
A variety of factors lead to this being the best choice of sensors:
•
Sensor junctions of very low mass can be easily fabricated. Lower mass
means quicker recognition of temperature changes.
•
Thermocouples are inherently rugged, requiring little in the way of special
handling precautions.
•
Thermocouple wire is inexpensive and readily available.
In keeping with this choice of sensors, the instrument is appropriately equipped
with:
•
Automatic reference junction compensation. Circuitry automatically
references to 0°C, regardless of ambient temperature.
•
Thermocouple break detection. Should the thermocouple break, the heater
power circuitry will be disabled, and a front panel indicator illuminated.
•
High impedance differential input circuitry. This circuitry allows the
instrument to tolerate floating or grounded thermocouples, with high
common-mode noise immunity.
The ease of fabrication for sensors compatible with the ITC is such that users can
seriously consider making their own. (In many cases, all that is needed is a small
torch, silver solder, and a roll of thermocouple wire.)
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