84
c
HAPTER
5:
Advanced Operation
Model 335 Temperature Controller
D
Point one:
calibration data point at or near the boiling point of nitrogen (77.35 K).
Acceptable temperature entries are 50 K to 100 K.
D
Point two:
calibration data point near room temperature (305 K). Acceptable tem-
perature entries are 200 K to 300 K.
D
Point three:
calibration data point at a higher temperature (480 K). Acceptable
temperature entries are 400 K to 600 K.
5.10.4 SoftCal™
Accuracy With
Platinum Sensors
A SoftCal™ calibration is only as good as the accuracy of the calibration points. The
accuracies listed for SoftCal™ assume ±0.05 K for 77.35 K (liquid nitrogen) and 305 K
(room temperature) points. If you are performing the SoftCal™ with Lake Shore
instruments, note that the boiling point of liquid cryogen, though accurate, is
affected by atmospheric pressure. Use calibrated standard sensors if possible.
One-point SoftCal™ calibrations with platinum sensors have no specified accuracy.
Two-point SoftCal™ calibrations for applications above 70 K are performed at liquid
nitrogen (77.35 K) and room temperature (305 K). Accuracy for the PT-102, PT-103, or
PT-111 platinum sensor is as follows:
Three-point SoftCal™ calibration
accuracy for DT-470-SD-13 diode sensors
±250 mK
70 K to 325 K
±500 mK
325 K to ±1400 mK at 480 K
(DIN class A or class B tolerance
Three-point SoftCal™ calibrations are performed at liquid nitrogen (77.35 K), room
temperature (305 K), and high temperature (480 K). Accuracy for the PT-102, PT-103,
or PT-111 platinum sensor is ±250 mK from 70 K to 325 K, and ±250 mK from
325 K to 480 K.
5.10.5 SoftCal™
CalibrationCurve
Creation
Once the calibration data points have been obtained, you may create a SoftCal™ cali-
bration. To create a SoftCal™ calibration, use this procedure:
1. Press
Curve Entry
, then scroll to SoftCal and press
Enter
.
2. A list of sensor types is displayed containing DT-470, PT-100, and PT 1000. Scroll
to the desired sensor type and press
Enter
.
3. Use the Store Curve To prompt to choose the user curve location in which to store
the newly generated curve.
4. If desired, use the Serial Number parameter to enter a serial number for the
newly generated curve.
5. Use the Point X Temp and Point X Sensor parameters to enter calibration data for
point X, where X can be point one, two, or three. If only one or two data points
were acquired, only enter those data points and leave the others at their default
values.
Review the acceptable temperature ranges for each calibration data point in FIGURE 5-9
and FIGURE 5-10. If a temperature value outside of the acceptable range is entered, the
value will be limited to the closest acceptable value.
6. Once the data points are entered, select yes at the Generate SoftCal prompt and
press
Enter
.
7. To cancel the operation, either choose No to the Generate SoftCal prompt, or
press
Escape
.
The Generate Softcal operation will overwrite an existing user curve. Please ensure the
curve number you are writing to is correct before generating the calibrated curve.
TABLE 5-8
