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4.5.6
Heater Output Display Units
The CONTROL DISPLAY FORMAT screen is also the place to select whether heater output is shown as
POWER or CURRENT. This setting will impact the heater output seen in the normal display and which units
are used for the manual output (MOut) display. If current is selected, the heater output and range will appear
as 20% @ 100 W to indicate 20% output current for the selected 100 watt range. If power is selected for the
same output, the heater output and range would appear as 4% of 100W to indicate 4% output power for the
selected 100 watt range.
To change the heater display units, press the Display Format key, then press the More key until you see the
CONTROL DISPLAY FORMAT screen. Press the Next Setting key until the Heat Display line is highlighted,
then use the s or t key to select Current or Power. Press the Enter or Next Setting key to continue with
other settings. Press the Save Screen key to store the changes. The default setting is Current.
4.5.7
Display Contrast
The Model 340 has a high contrast, LCD display with a bright backlight. The factory contrast setting is good
for most applications, but it will need to be changed for arrangements of equipment that put the Model 340
well above or below eye level. Display contrast can be set to a value between 0 an 100. Please note that
changing contrast has no effect on the display backlight.
To change display contrast, press the Display Format key then press the More key until the Misc. Display
Format screen is displayed. Press the Next Setting key until the Contrast line is highlighted, then use the
s or t key to adjust contrast. The contrast will change as the parameter is being set, so adjustments should
be made with the operator and instrument in their normal positions. Press the Enter or Next Setting key to
continue with other settings. Press the Save Screen key to store the changes in the Model 340. The default
setting is 50.
4.5.8
Display Backlight On/Off
The Model 340 display used a florescent tube as a backlight. The backlight is powered with a high voltage
supply operating at 30 kHz. Some experiments are sensitive to noise in the frequency range of 30 kHz, so the
backlight power supply can be turned off. Please note that the display is unreadable when the backlight is off.
To turn the display backlight off, press the Display Format key, then press the More key to show the MISC.
DISPLAY FORMAT screen. Press the Next Setting key until the line for backlight is highlighted, then use the
s or t key to turn the backlight off. Press the Save Screen key to store the changes. Default setting is On.
To turn the display backlight back on, press any key on the keypad.
4.5.9
Locking the Keypad
The Model 340 has a keypad lock feature to prevent accidental changes to instrument parameters and
minimize the disturbances of curious onlookers. A simple 3 number sequence is the code needed to lock and
unlock the keypad. The factory default code is 123 and it can only be changed using a computer interface.
To lock or unlock the keypad, press the Display Format key then press the More key to show the Misc.
Display Format screen. Press the Next Setting key until Lock is highlighted, then use the s or t key to
toggle the lock setting. Press the Enter key. A small setting window will appear for entering a three digit
number code. Use the number keys to enter the code, then press the Enter key. Press the Save Screen key
to store the lock status in the Model 340. The default setting is unlocked, code 123.
When the keypad is locked, you can still see values for the various parameters, you just cannot change them.
The only front panel keys that are active when the keypad is locked are the Heater Off and Alarm Reset keys.
4.6
DEFAULT VALUES
It is sometimes necessary to reset instrument parameters to their factory default values. These values can be
cleared without affecting instrument calibration.
To reset the Model 340 parameters to factory default values, press the Options key then press the More key
until the Revision Information screen is displayed. Up the s or t key to change the Set Defaults setting to
Yes, then press the Enter key. Press the Save Screen key to complete the action. The Model 340 will then
restart using the factory default values.
4-8
Lake Shore Model 340 Temperature Controller User's Manual
Front Panel Operation
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Table of Contents
Troubleshooting
