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TECPak
User’s Manual
Using the Analog Interface
The Analog Interface is a feature not found on our bench top temperature
controllers, as it is designed to be used in applications where a user interface, or
even a PC, is not required.
The Analog Interface has two sections: the logic level control/status pins, and
the analog control/monitor pins, plus an auxiliary power supply. The +5V
auxiliary supply is provided for external low-power electronics. Current draw on
this supply must not exceed 100mA. The Ground pin provides the ground
reference for both the logic level and analog inputs and outputs.
The logic level inputs operate off a low or high voltage input. A logic zero (below
1V) is considered to be off or false, while a logic one (above 2.5V, but do not
exceed 5V) is considered to be on or true. For logic level outputs, a false will be
0V, while a true will be 3.3V.
There are three logic level pins:
On/Off Control Input
This input controls the on/off state of the instrument. When this input
transitions from off to on, then the TEC output is turned on, and begins
controlling to the temperature set point. Similarly, when it transitions from
on to off, the output is turned off.
It is possible to use the analog interface with the computer interface, as the
TECPak
is looking for a
change
in the logic input to turn the output on or
off, as appropriate (considered an
edge
triggered input, rather than a
level
triggered input). It is possible for the computer interface to turn the output
on or off as well, ignoring the steady state of the logic input. However, as
soon as the logic input changes state, then the
TECPak’s
output will also
be changed to reflect the new state.
For example, if the logic input goes from false to true (turn the output on),
then the output will be turned on. Later, if a TEC:OUT OFF is received from
the computer (turn the output off), then the output will be turned off,
even
though the logic input is still high.
Likewise, if the computer sends a
TEC:OUT ON, the output will be turned on, regardless of the logic input’s
CAUTION
Do not exceed 5V DC on any logic input pin or 3V DC on
any analog input pin, or damage to the instrument may
occur.
