Lake Shore Model 218 Temperature Monitor User’s Manual
Special Features
5-1
CHAPTER 5
SPECIAL FEATURES
5.0 GENERAL
This chapter covers Front Panel Curve Entry in Paragraph 5.1, SoftCal™ in Paragraph 5.2, Data
Logging in Paragraph 5.3, and Printing in Paragraph 5.4. Most users will not find it necessary to use
these special features during normal operation.
5.1 FRONT PANEL CURVE ENTRY
A unique 200 point user curve can be stored for each of the eight inputs. CalCurves™ for Lake Shore
calibrated sensors can be stored as user curves. The built in SoftCal™ algorithm (Paragraph 5.2) uses
the same memory space so it is not possible to enter a user curve and SoftCal™ curve for the same
input. User curves must be stored in the same location number as the sensor input. Once an
appropriate user curve is stored for a sensor input it can be selected just like standard curves. A user
curve may not be shared between multiple inputs.
Collect and format all necessary information on paper before beginning the entry process. Curve
header information cannot be overlooked; it is as important to proper operation as the data breakpoints.
Enter curve data breakpoints in increasing sensor units order. Other instruments use this curve data
format and curve breakpoints may be entered that are beyond the Model 218 reading capability.
5.1.1 Curve Header Parameters
Curve Number:
User curves accessed from the front panel are numbered by sensor input (
1-8
).
When accessed over the computer interface, they are numbered from
21
to
28
.
Name:
Defaults to the name
User Curve
for front panel entry. When entering a user curve over the
computer interface, a curve name of up to 15 characters can be entered.
Serial Number:
Up to a 10-character sensor serial number. Both numbers and letters can be entered
over computer interface, only numbers can be entered from the front panel.
Format:
The format parameter tells the instrument what breakpoint data format to expect. Different
sensor types require different formats. Formats for Lake Shore sensors are:
V/K:
Volts vs. Kelvin for Diode sensors.
Ω
/K:
Resistance vs. Kelvin for platinum RTD sensors.
Log
Ω
/K:
Log Resistance vs. Kelvin for NTC resistive sensors.
Limit:
Enter a temperature limit in Kelvin for the curve. Default is 375 K. Enter a setting of 9999.9 K if
no limit is needed. This parameter is not used by the Model 218.
Temperature Coefficient:
The unit derives the temperature coefficient from the first two breakpoints.
The user does not enter this setting. If it is not correct check for proper entry of those points. A
positive coefficient (
P
) indicates that the sensor signal increases with increasing temperature. A
negative coefficient (
N
) indicates that the sensor signal decreases with increasing temperature.
Table 5-1. Typical Curve Parameters
Type
Typical
Lake Shore
Model
Units Format Limit
(K)
Temperature
Coefficient
Typical
Sensor Resolution
Silicon Diode
DT-470
Volts
V/K
475
Negative
0.00001 (V)
GaAlAs Diode
TG-120
Volts
V/K
475
Negative
0.00001 (V)
Platinum 100
PT-100
Ohms
Ω
/K 800 Positive
0.001
(
Ω
)
Platinum 1000
PT-100
Ohms
Ω
/K 800 Positive
0.01
(
Ω
)
Rhodium-Iron RF-800-4
Ohms
Ω
/K 400 Positive
0.001
(
Ω
)
Carbon-Glass CGR-1-500
Ohms
Log
Ω
/K 325 Negative 0.00001(Log
Ω
)
Cernox™ CX-1050
AA
Ohms
Log
Ω
/K 325 Negative 0.00001(Log
Ω
)
Ruthenium Oxide
-
Ohms
Log
Ω
/K 300 Negative 0.00001(Log
Ω
)
Germanium GR-200A-1000
Ohms
Log
Ω
/K 40 Negative 0.00001(Log
Ω
)
