Softcal™ With Platinum Sensors; Softcal™ Accuracy With Platinum Sensors - Lakeshore 336 User Manual

90 c 5: Advanced Operation
HAPTER
5.10.3 SoftCal™ With
Platinum Sensors
5.10.4 SoftCal™
Accuracy With
Platinum Sensors
Model 336 Temperature Controller
The platinum sensor is a well-accepted temperature standard because of its consis-
tent and repeatable temperature response above 30 K. SoftCal™ gives platinum sen-
sors better accuracy than their nominal matching to the DIN 43760 curve.
SoftCal Point One
Liquid nitrogen
boiling point
77.35 K
0 50 100 150
50 – 100 K
FIGURE 5-9 Acceptable temperature range for platinum SoftCal™ sensors
One, two, or three calibration data points can be used. If you are using one point, the
algorithm shifts the entire curve up or down to meet the single point. If you are using
two points, the algorithm has enough information to tilt the curve, achieving good
accuracy between the data points. The third point extends the improved accuracy to
span all three points.
Point 1: calibration data point at or near the boiling point of nitrogen (77.35 K).
D
Acceptable temperature entries are 50 K to 100 K.
Point 2: calibration data point near room temperature (305 K). Acceptable tem-
D
perature entries are 200 K to 300 K.
Point 3: calibration data point at a higher temperature (480 K). Acceptable tem-
D
perature entries are 400 K to 600 K.
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:
±250 mK 70 K to 325 K
±500 mK 325K to ±1400 mK at 480 K
(DIN class A or class B tolerance
TABLE 5-8 Three-point SoftCal™ calibration
accuracy for DT-470-SD-13 diode sensors
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.
SoftCal Point Two
Room temperature
point
305 K
200 250 300 350 400
200 – 325 K
SoftCal Point Three
High temperature
point
480 K
450 500 550 600
400 – 600 K
650