Add A New Breakpoint Pair; Delete A Breakpoint Pair; Thermocouple Curve Considerations - Lakeshore 335 User Manual

80 c 5: Advanced Operation
HAPTER
Model 335 Temperature Controller

5.9.1.2 Add a New Breakpoint Pair

The last breakpoint of a curve is signified by the first pair that contains a 0 value for
both the temperature and sensor portions. Curves are limited to 200 breakpoint
pairs, so if 200 pairs already exist, then the 200th pair will be the last pair in the list.
To add a new breakpoint pair to a curve that has less than 200 pairs, scroll to the end
of the list and edit the 0 value pair by following the procedure for editing a breakpoint
pair in section 5.9.1.1. If the curve still contains less than 200 pairs, a new 0 value
breakpoint will be added to the end of the list for entering another new
breakpoint pair.
Menu Navigation:
Curve Entry QEdit (21–59)
Interface Command: CRVPT

5.9.1.3 Delete a Breakpoint Pair

To delete a breakpoint pair, scroll to the desired breakpoint number, then enter a 0
value for both the sensor and temperature values by following the procedure for edit-
ing a breakpoint pair in section 5.9.1.1.
If you do not enter 0 for both sensor and temperature values, then entering new values
over an existing breakpoint pair will replace that pair with the new value when you press
the Enter key.
After editing, adding, or deleting all desired breakpoint pairs, press Escape while the
highlight is on a breakpoint number. All breakpoint pair changes, additions, and dele-
tions will be saved when exiting the menu.
When curve entry is complete, assign the new curve to an input. The Model 335 does
not automatically assign the new curve to any input. Refer to section 4.4.7 for details
on assigning a curve to a sensor input.
Menu Navigation:
Curve EntryQEdit (21–59)
Interface Command: CRVPT

5.9.1.4 Thermocouple Curve Considerations

The following are things to consider when generating thermocouple curves.
Users may enter temperature response curves for all types of thermocouples.
D
Enter curve data in mV/K format with thermocouple voltage in millivolts and
temperature in kelvin.
The curve must be normalized to 0 mV at 273.15 K (0 °C). Thermocouple voltages
D
in millivolts are positive when temperature is above 273.15 K and negative when
temperature is below that point.
To convert curves published in Celsius to kelvin, add 273.15 to the temperature in
D
Celsius.
The input voltage of the Model 335 is limited to ±50 mV, so any part of the curve
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that extends beyond ±50 mV is not usable by the instrument.
A message of S.OVER or S.UNDER on the display indicates that the measured ther-
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mocouple input is over or under the ±50 mV range.
QCurve Points (1–200)
ENTER
Q Curve Points (1– 200)
ENTER