Lake Shore Model 370 AC Resistance Bridge User’s Manual
5.1.3 CalCurve™
The CalCurve service provides the user with a convenient way get the temperature response curve from Lake Shore
calibrated sensors into instruments like the Model 370. It can be performed at the factory when calibrated sensors and
instruments are ordered together. The factory installed CalCurve option is Model 8001-370 and should be ordered with a
calibrated sensor. A CalCurve can be done in the field when additional or replacement sensors are installed. Curve data
is loaded into some type of non-volatile memory that is installed into the instrument by the user. In the case of the Model
370, the curve is loaded into a non-volatile memory, which can be installed into the instrument. The field installed
version is a Model 8002-05-370 and should be ordered with a calibrated sensor. Customers that have a PC-compatible
computer with an RS-232C or IEEE-488 interface have another option. The Model 8000 is included with the calibrated
sensor and can be loaded by the user. Lake Shore offers a free curve loading program that is compatible with Model
8000 CalCurves.
5.2
FRONT PANEL CURVE ENTRY OPERATIONS
There are three operations associated with front panel curve entry: Edit curve, Copy curve and Erase curve as detailed
below. Similar operations are available over computer interface.
Edit Curve
Edit allows the user to enter or edit a curve at any user curve location.
Refer to Paragraph 5.2.1
Erase Curve
Erase allows the user to delete a curve from any user curve location.
Refer to Paragraph 5.2.2
Copy Curve
Copy allows the user to copy a curve from any location to any other
curve location.
Refer to Paragraph 5.2.3
5.2.1 Edit
Curve
The Edit Curve operation is used to enter a new curve or edit an existing user curve. Any user curves (1 to 20) can be
changed. Entering the identification parameters associated with the curve is as important as entering the breakpoints.
Curve header parameters are listed in Table 5-1. Typical parameters for common sensors are listed in Table 5-2. Read
this section completely and gather all necessary data before beginning the process.
NOTE:
If the curve you wish to enter has similar parameters to an existing curve, first copy the similar curve
(as described in Paragraph 5.2.3) to a new location, then edit the curve to the desired parameters.
Table 5-1. Curve Header Parameters
Name
The curve name cannot be changed from the front panel. Curve names can only be entered over the
computer interface (up to 15 characters). The default curve name is User Curve xx, where xx is the
curve number.
Serial
Number
Specific sensors serial numbers (up to 10 characters). The serial number field accepts both numbers and
letters over computer interface, but the instrument front panel enters only numbers. The default is blank.
Curve
Format
The instrument must know the data format of the curve breakpoints. Different sensor types use different
data formats. The 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
Ω
/K
Resistance vs. Kelvin
10 k (
Ω
) 0.001
(
Ω
)
log R/K
log Resistance vs. Kelvin
7 (log R)
0.00001 (log R)
Setpoint
Limit
A setpoint temperature limit can be included with every curve. When controlling in temperature, the
setpoint cannot exceed the limit entered with the curve for the control sensor. The default is 375 K. Set
to 9999 K if no limit is required.
Temperature
Coefficient
The instrument derives the temperature coefficient from the first two breakpoints. If set improperly,
check the first 2 breakpoints. A positive coefficient indicates the sensor signal increases with increasing
temperature. A negative coefficient indicates the sensor signal decreases with increasing temperature.
5-2
Advanced Operation
