Lake Shore Model 340 Temperature Controller User’s Manual
1-6
Introduction
1.3.11 Internal Programming
The Model 340 can run a set of instrument instructions called an internal program. Each program represents
the temperature changes needed to do a users experiment. Setpoint can be changed or ramped up and down
and other controller parameters can be programmed. For simple experiments the internal program eliminates
the need for computer control. It is also common for the internal program to be used with computer control so
the computer is not slowed down by temperature control overhead.
1.3.12 Math
Some math features are included to improve usability and aid in setting up experiments. It can be useful to
have reading filters and maximum and minimum calculations easily available on the front panel. The Model
340 also computes a linear equation on reading data to allow some flexibility in how the display represents
experimental inputs. The Model 340 does not include the ability to do significant data manipulation. Serious
numerical analysis must be done off line.
1.3.13 Alarms, Analog Outputs, and Digital I/O
A clear example of the commitment to making the Model 340 a real part of the experimental environment is
the inclusion of analog and digital (TTL level) inputs and outputs. These features are not needed for a typical
temperature control loop but they provide an effective interface to other experimental hardware at relatively
low cost to the user. Relays can be tied to temperature alarms or opened and closed manually. Analog
outputs can transmit temperature to data recorders or be used as a variable voltage source. Digital inputs and
outputs can improve the efficiency of external sensor scanning or be used to set and monitor system function.
1.3.14 Memory Card
A memory card slot conforming to PCMCIA pin out is included for special instrument applications. The slot is
not a general purpose PCMCIA interface. Supported applications include data logging, curve transfer and
loading, saving and restoring instrument setup.
1.3.15 Computer Interface
The Model 340 has two types of computer interfaces. The parallel interface conforms to IEEE-488.2 standard
unless otherwise specified. The IEEE-488 interface is high speed and allows for multiple instruments to
communicate on the same bus. It is commonly used with laboratory instrumentation. Necessary interface
hardware is not included with most personal computers so it must be added with a third party card.
The serial interface conforms to
RS-232C electrical format included
with most personal computers. Serial
interfaces are much faster now than
they were just a few years ago but
this interface is less common in
laboratories because only one
instrument can communicate per
channel.
Either interface can send settings to
the Model 340 and collect reading
data back from it. Every attempt is
made to allow full access to
instrument features so it can be fully
involved in computer controlled
experiments. Even the analog
outputs and digital inputs and outputs
(I/O) can be controlled by computer
interface.
Table 1-1. Comparison of Control Loops 1 and 2
Hardware Features
Loop 1
Loop 2
Control Output
Heater Output
Analog Output 2
Maximum Output Power
100 W
1 W
Output Type
Current Source
Voltage Source
Multiple Output Ranges
Yes
No
Software Features
Loop 1
Loop 2
PID Control
Yes
Yes
AutoTune Yes
Yes
Zone Tuning
Yes
Yes
Ramping Yes
Yes
Internal Programming
Yes
No
Open Loop Control
Yes
Yes
Display in Current or Power
Yes
No
Large Display
Yes
Yes
Setpoint Limit
Yes
Yes
Slope Limits
Yes
Yes
Heater Range Limit
Yes
No
Control Loop Filter
Yes
Yes