1.1.2 Temperature Control
3
|
www.lakeshore.com
1.1.2 Temperature
Control
Providing a total of 75 W of heater power, the Model 335 is the most powerful half
rack temperature controller available. Designed to deliver very clean heater power,
precise temperature control is ensured throughout your full scale temperature range
for excellent measurement reliability, efficiency and throughput. Two independent
PID control outputs can be configured to supply 50 W and 25 W or 75 W and 1 W of
heater power. Precise control output is calculated based on your temperature set-
point and feedback from the control sensor. Wide tuning parameters accommodate
most cryogenic cooling systems and many high-temperature ovens commonly used
in laboratories. PID values can be manually set for fine control or the improved auto-
tuning feature can automate the tuning process.
The Model 335 autotuning method calculates PID parameters and provides feedback
to help build zone tables. The setpoint ramp feature provides smooth, continuous set-
point changes and predictable approaches to setpoint without the worry of over-
shoot or excessive settling times. The instrument’s zone tuning feature automatically
switches temperature sensor inputs when your temperature range goes beyond the
useable range of a given sensor. This feature combined with the instrument’s ability
to scale the sensor excitation through ten pre-loaded current settings allows the
Model 335 to provide continuous measurement and control from 300 mK to 1505 K.
Both control outputs are variable DC current sources referenced to chassis ground. As
a factory default, Outputs 1 and 2 provide 50 W and 25 W of continuous power
respectively, both to a 50
)
or 25
)
load. For increased functionality, Output 2 can
also be set to voltage mode. When set to voltage mode, it functions as a ±10 V analog
output while still providing 1 W of heater power and full closed loop PID control capa-
bility. While in this mode, output 1 can provide up to 75 W of heater power to a
25
)
load.
Temperature limit settings for inputs are provided as a safeguard against system
damage. Each input is assigned a temperature limit, and if any input exceeds that
limit, both control channels are automatically disabled.
1.1.3 Interface
The Model 335 is standard equipped with universal serial bus (USB) and parallel
(IEEE-488) interfaces. In addition to gathering data, nearly every function of the
instrument can be controlled via computer interface. You can download the
Lake Shore curve handler software program to your computer to easily enter and
manipulate sensor calibration curves for storage in the instrument’s non-volatile
memory.
The USB interface emulates an RS-232C serial port at a fixed 57,600 baud rate, but
with the physical plug-ins of a USB. It also allows you to download firmware
upgrades, ensuring the most current firmware version is loaded into your instrument
without having to physically change your instrument.
Both sensor inputs are equipped with a high and low alarm which offers latching and
non-latching operation. The two relays can be used in conjunction with the alarms to
alert you of a fault condition and perform simple on-off control. Relays can be
assigned to any alarm or operated manually.
The ±10 V analog voltage output can be configured to send a voltage proportional to
temperature to a strip chart recorder or data acquisition system. You may select the
scale and data sent to the output, including temperature or sensor units.
