Lake Shore Model 340 Temperature Controller User’s Manual
Measurement Operation
5-3
Table 5-2. Special Sensor Type Configuration
Excitation Input
Range
Temperature Coefficient
Units
1 mA
300 µA
100 µA
30 µA
10 µA
3 µA
1 µA
300 nA
100 nA
30 nA
*10 mV
*1 mV
5 V
2.5 V
1 V
500 mV
250 mV
100 mV
50 mV
25 mV
10 mV
5 mV
2.5 mV
1 mV
Positive
Negative
Volts
Ohms
The columns in the above table can be selected independently. When voltage units are selected the input
range is as listed in the table. When resistance units are selected, resistance range can be computed as
R = V/I. Again, it is up to the user to determine the suitability of a special input configuration. Input
configurations that indicate a resistance range of more than 1 M
Ω
are not recommended because the
instrument itself will begin to cause measurement errors.
To select a special sensor type, press the
Input Setup
key. The input setup setting screen will appear with
the input letter in the top left hand corner. Use the
s
or
t
key to select an input. Press the
Enter
key or the
Next Setting
key to display the input parameters for that input. Press the
Next Setting
key until the type field
is highlighted and then use
s
or
t
key to select special from the list of settings. Press the
Enter
key or the
Next Setting
key and to advance to the next parameter. Set the parameters of units, temperature coefficient,
excitation and input range from the list in the table above. If special setup was successful, proceed to
temperature response curve selection in Paragraph 5.2 by pressing the
Previous Setting
key or press the
Save Screen
key to store the changes in the Model 340.
5.1.5 Turning an Input Off
There are cases, particularly when using scanned inputs, that the user may wish to turn off an input. This can
be done from the input setup screen. If an input that has been turned off is chosen for the display, the
DISABLE
message will appear in the reading field.
To turn an input off, press the
Input Setup
key. The
INPUT SETUP
screen will appear with the input letter in
the top left hand corner. Use the
s
or
t
key to select input
A
or
B
. Press the
Enter
or
Next Setting
key until
the
Enable
field is highlighted. Use the
s
or
t
key to select
OFF
. Press the
Save Screen
key to store the
change in the Model 340.
5.2 SELECTING A TEMPERATURE RESPONSE CURVE
A temperature response curve is needed to convert a sensor reading in sensor units to temperature. A curve
is a table of breakpoints, each containing a temperature value and its sensor units equivalent for the sensor.
The section on sensor selection discusses different ways of obtaining temperature response curves. Curves
can also be created by the user and entered into the instrument as described in the curve entry section. It is
assumed that an appropriate curve is present in the Model 340 before proceeding with this section.
Some types of sensors behave in a predictable manner and a standard temperature response curve can be
created for them. The Model 340 has standard curves included in firmware. Refer to Table 5-3. Details on
standard curves are provided in Appendix B.
Curves entered by the user or loaded as CalCurves will appear during curve selection list. They will have
curve number 21 to 60. The sensor serial number will appear on the setting screen and can be used to
identify a unique curve if the serial number was included with the curve table.
NOTE:
During curve selection, the instrument may only show the curves that are appropriate for an
input type. It is necessary to select an appropriate input type before selecting a curve. Refer to
Paragraph 5.4 for a description of how to select multiple curves for a scanned input.