Lake Shore Model 340 Temperature Controller User’s Manual
6-2 Temperature Control Operation
6.1.4 Control Output Display
The Model 340 shows the control output value on the display so the operator can monitor the control loop
performance during an experiment or while tuning. The output value is shown on the display whenever loop
parameters for that loop are shown. Control output can also be shown on the display using large characters.
Refer to Paragraph 4.5 for display format.
If the message “Disabled” appears in the control output field of the display, the control loop must be enabled
from the CONTROL SETUP screen before it is operational, refer to Paragraph 6.2. (There is an enable
setting for each control loop and it is independent of heater range.)
Hardware included in the heater output circuit allows more features in monitoring and displaying control
output for Loop 1. If the correct value of heater resistance is entered, the heater output can be shown on the
display in power. To change heater output units, refer to Paragraph 4.5.6. The heater output is reported in
percent of full scale current or power for a given heater range. Full scale for the range is shown on the display
to indicate which range is selected. An A/D converter in the heater output circuitry also allows the Model 340
to diagnose problems in the heater circuit. If an error is detected, a message appears in the control output
field of the display. These errors are summarized in Paragraph 11.9. Error messages are not possible for
Loop 2. When Analog Output 2 is used for control output of Loop 2, the control output is reported in percent of
full scale output voltage.
6.2 CONTROL LOOP ENABLE
As a safety feature, both Control Loop 1 and 2 default to the disabled state. This state ensures that the heater
output for Loop 1 is off and Analog Output 2 for Loop 2 is set to zero volts. The user must enable a control
output before it can be used. If an output is disabled, the message Disabled appears in the control output field
of the display.
To enable or disable a control output, press the Control Setup key. The CONTROL SETUP screen is
displayed. The control loop indicator is highlighted in the upper left hand corner. Use s or t key to select
Loop 1 or 2. Press the Enter or Next Setting key. The control setup parameters for that loop appear on the
screen. Press the Next Setting key until the Enable field is highlighted. Use the s or t key to select ON for
enabled or OFF for disabled. Press the Enter or Next Setting key to continue with more settings, or press the
Save Screen key to store the changes in the Model 340. The default setting is Off.
Some systems require that a control output remains off if power is lost. The power up enable feature enables
the user to choose whether or not they want the control output to be disabled each time the instrument power
is turned off then on. Setting the power up parameter to off disables the control output on power up. Setting
the power up parameter to on enables the control output on power up.
To change the power up setting, press the Control Setup key. The CONTROL SETUP screen is displayed.
The control loop indicator is highlighted in the upper left hand corner. Use the s or t key to select Loop 1 or
2. Press the Enter or Next Setting key. The control setup parameters for that loop appear on the screen.
Press the Next Setting key until the Power Up field is highlighted. Use the s or t key to select on or off.
Press the Enter or Next Setting key to continue with more settings, or press the Save Screen key to store
the changes in the Model 340. The default setting is Off.
6.3 CONTROL LOOP FILTER
The control loop filter quiets feedback sensor noise that causes instability in the control loop. The control filter
works best on electrical noise from the environment or noise in temperature measurement. The control filter
can worsen control stability when unwanted disturbances exist in the load temperature because filtering
reduces the control loop bandwidth.
The control loop filter uses the same filter window and number of filter points as the input chosen as the
control channel. It can be turned on or off independently from the input filter.
To turn the control loop filter on or off, press Control Setup to display the CONTROL SETUP screen with the
control loop indicator highlighted in the upper left hand corner. Use the s or t key to select Loop 1 or 2.
Press Enter or Next Setting to display control setup parameters for that loop. Press Next Setting until the
Filtered field highlights. Use the s or t key to select ON or OFF. Press Enter or Next Setting to continue
with more settings, or press Save Screen to store changes in the Model 340. The default setting is Off.
To Next Page
Loading...
