Lake Shore Model 340 Temperature Controller User’s Manual
8-2
Instrument Programming
8.1.3 Front Panel Curve Edit
The
Edit curve
operation can be used to enter a new curve or edit an existing user curve. Entering the
identification parameters associated with the curve is as important as entering the breakpoints. Only user
curves (numbers 21 to 60) can be changed. Standard curves can only be viewed with the edit operation.
Name:
Identify curves with names of up to 15 characters. The curve name cannot be changed
during front panel curve entry. To change curve names, enter them over computer interface.
The default curve name is User xx, where xx is the curve number.
SN:
Identify specific sensors with serial numbers of up to 10 characters. The serial number field
accepts both numbers and letters, but the instrument front panel enters only numbers. To
enter both numbers and letters enter curves over computer interface. The default is blank.
Limit
A setpoint temperature limit can be included with every curve. If the control sensor is an
input using a curve and operating in temperature units, then the setpoint cannot exceed the
limit entered with the curve. The default is 375 K.
Format:
The instrument must know the data format of the curve breakpoints. Different sensor types
use different data formats. The standard sensor inputs require one of the formats below. The
range and resolution specified are not always available at the same time. Practical range
and resolution depend on the sensor type.
Sensor Units
Sensor Units
Format
Description
Full Scale Range
Maximum Resolution
V/K
Volts vs. Kelvin
10 (V)
0.00001 (V)
Ω
/K
Resistance vs. Kelvin
10 k (
Ω
) 0.00001
(
Ω
)
log R/ K
log Resistance vs. Kelvin
4 (log R)
0.00001 (log R)
log R / log K
log Resistance vs. log Kelvin
4 (log R)
0.00001 (log R)
mV/K
mV vs. Kelvin
±100 (mV)
0.00001 (mV)
Coeff:
Enter an appropriate temperature for proper temperature control. A positive coefficient
indicates the sensor signal increases with increasing temperature. A negative coefficient
indicates the sensor signal decreases with increasing temperature. The instrument derives
the temperature coefficient from the first two breakpoints. If it is set improperly, check the
first two breakpoints.
Table 8-1. Recommended Curve Parameters
Type
Lake Shore
Model No.
Units Format Limit
(K)
Coefficient
Recommended
Sensor Resolution
Silicon Diode
DT-470
Volts
V/K
475
Negative
0.00001 (V)
GaAlAs Diode
TG-120
Volts
V/K
325
Negative
0.00001 (V)
Platinum 100
PT-100
Ohms
Ohm/K
800
Positive
0.001 (
Ω
)
Platinum 1000
PT-100
Ohms
Ohm/K
800
Positive
0.01 (
Ω
)
Rhodium-Iron RF-100
Ohms
Ohm/K
325
Positive
0.001
(
Ω
)
Carbon-Glass CGR-1-1000
Ohms logR/K 325 Negative
0.00001(logR)
Cernox CX-1030
Ohms
logR/K 325 Negative
0.00001(logR)
Ruthenium Oxide
-
Ohms
logR/K
325
Negative
0.00001(logR)
Germanium GR-200A-100
Ohms
logR/K 325 Negative
0.00001(logR)
Once curve identification parameters are entered, it is time to enter curve breakpoints. A breakpoint is the
representation of the sensor calibration that is stored in the instrument. Each breakpoint consists of one value
in sensor units and one temperature value in kelvin. From 2 to 200 breakpoints can be entered as a curve. No
special endpoints are required. Sensor units are defined by the format setting in Table 8-1.
Breakpoint setting resolution is six digits in temperature. Most temperature values are entered with 0.001
resolution. Temperature values of 1000 K and greater can be entered to 0.01 resolution. Temperature values
below 10 K can be entered with 0.0001 resolution. Temperature range for curve entry is 1500 K.