Lake Shore Model 340 Temperature Controller User’s Manual
Cooling System Design
2-3
2.2.2 SoftCal™
SoftCal is a good solution for applications that do not require the accuracy of a traditional calibration. The
SoftCal algorithm uses the well behaved nature of sensors that follow a standard curve to improve the
accuracy of individual sensors. A few known temperature points are required to perform SoftCal.
Lake Shore sells SoftCal calibrated sensors that include both the large interpolation table and the smaller
breakpoint interpolation table. A CalCurve, described in Paragraph 2.2.4, may be required to get the
breakpoint table into a Model 340 where it is called a temperature response curve.
The Model 340 can also perform a SoftCal calibration. The user must provide one, two, or three known
temperature reference points. The range and accuracy of the calibration is based on these points.
Lake Shore DT-400 Series
Silicon Diode Temperature Sensor
Standard
SoftCal™ Calibration
Precision Calibration
Standard sensors are inter-
changeable within the publish-
ed tolerance band. Below are
Standard Curve 10 Tolerance
(Accuracy) Bands for DT-470.
A 2-point SoftCal™ uses data
points at 77.35 K and 305 K. A 3-
point SoftCal™ uses data points at
4.2 K, 77.35 K, and 305 K.
Lake Shore can calibrate most
sensors with up to 200 data points
and can concentrate data-taking in
specific areas of interest.
Generate a CalCurve™ for either
SoftCal™ or Precision Calibration.
CalCurve
™
There are 3 ways to improve
temperature sensor accuracy:
8001
8000
3405-128F-CALCRV
Breakpoint pairs
are factory-
loaded in non-
volatile memory.
Breakpoint pairs are
loaded on a Floppy Disk
in ACSII format for
Customer downloading.
Breakpoint pairs
are loaded in a
Datacard for field
installation.
Band
2 K* -
100 K
100 K -
305 K
305 K -
375 K
11
±0.25 K
±0.5 K
±1.0 K
11A
±0.25 K
±1% of Temp.
12
±0.5 K
±1.0 K
±2.0 K
12A
±0.5 K
±1% of Temp.
13
±1 K
±1% of Temp.
To increase accuracy,
perform a SoftCal™ with the
controller and sensor. After
sensor calibration, the
custom curve for that sensor
replaces the standard Curve
10.
* Temps down to 1.4 K only with
Precision Calibrated Sensors.
User calculates break-
points and manually enters
data into the controller
Enter the voltage at 2 or 3 data
points into a SoftCal™ capable
controller. A calibration report is
sent with the sensor.
±1.0 K
2 K to <30 K
±0.25 K
30 K to <60 K
±0.15 K
60 K to <345 K
±0.25 K
345 K to <375 K
±1.0 K
375 K to 475 K
Typical 2-Point Accuracy
±0.5 K
2 K to <30 K
±0.25 K
30 K to <60 K
±0.15 K
60 K to <345 K
±0.25 K
345 K to <375 K
±1.0 K
375 K to 475 K
Typical 3-Point Accuracy
Lake Shore fits a curve to these
points, and sends a detailed report
to the sensor that includes Raw
Temperature Data, Polynomial
Fits, and Interpolation Tables.
<10 K
12 mK
20 mK
10 K
12 mK
20 mK
20 K
15 mK
25 mK
30 K
25 mK
45 mK
50 K
30 mK
55 mK
100 K
25 mK
50 mK
300 K
25 mK
50 mK
340 K
—
100 mK
480 K
—
100 mK
Typical Precision Cal. Accuracy
Temp.
Typical
Maximum
- or -
Model Number
340-2-1.eps
Figure 2-1. Silicon Diode Sensor Calibrations and CalCurve