
Operation
3-17
Temperature displays
It is important to keep in mind that, with the Model 1801
enabled, the Model 2001 always displays the difference in
temperature between the reference thermocouple and the
measuring thermocouple in the currently selected temper-
ature units (°C, °F, or K). This characteristic may result in
confusion, particularly when temperature units are
changed.
As an example, assume that the reference thermocouple is
located in an ice-point reference at 0°C (32°F), and that
the measuring thermocouple is at 23°C (73.4°F). With °C
units selected, the instrument will, of course, display a
differential temperature of 23°C. If the display units are
then changed to °F, the displayed temperature now
becomes 41.4°F (73.4 - 32 = 41.4).
Example 1: °C Display
Reference thermocouple temperature: 23°C
Measuring thermocouple temperature: 45°C
Displayed temperature: 22°C
Example 2: °F Display
Reference thermocouple temperature: 73.4°F
Measuring thermocouple temperature: 113°F
Displayed temperature: 39.6°F
Example 3: K Display
Reference thermocouple temperature: 296K
Measuring thermocouple temperature: 318K
Displayed temperature: 22K
Temperature bar graph displays
When the Model 1801 is enabled, the temperature bar
graph display limits are reduced to reflect the ±50°C tem-
perature range of the Model 1801 regardless of the normal
range of the selected thermocouple type. Otherwise, the
temperature bar graphs operate essentially in the same
manner as described in paragraph 3.3.2 of the Model 2001
Operator’s Manual.
IEEE-488 bus temperature commands
Table 3-9 summarizes additional bus commands associ-
ated with the Model 1801 temperature measurement func-
tion. The :DTC:TYPE command is used to select the type
of thermocouple to be used for the differential tempera-
ture measurement. If you select one of the standard ther-
mocouple types (J, K, T, E, R, S, or B), you must also
program the reference thermocouple temperature using
the :DTC:RTEM command. If you choose the USER ther-
mocouple type, you must also program the slope (coeffi-
cient) of the thermocouple using the :DTC:USLOPE
command. Note that the slope is programmed in V/°C
over the bus instead of the µV/°C units used from the front
panel.
Example 1: Select Thermocouple Type
The following command would be sent to select a J-type
thermocouple:
:TEMP:DTC:TYPE J
Example 2: Program Reference Temperature
The following command would be sent to program a ref-
erence temperature of 23°:
:TEMP:DTC:RTEM 23
Example 3: Program User Thermocouple Slope
The command below will program a thermocouple slope
of 10µV/°C:
:TEMP:DTC:USL 10E-6
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