Time Constant - Fluke 1551A Ex User Manual

 1552A Ex: Maximum immersion: 75 mm less than total probe length.
 1551A Ex: Maximum immersion: 50 mm less than total probe length.

Time Constant

The different probe sizes of the Thermometer exhibit different settling time constants.
This parameter describes the time it takes for the Thermometer to change 63 % toward its
final temperature (see ASTM E644). The time constant depends on the diameter of the
metal sheath of the Thermometer. Typical time constants are given in Table 2.
Sheath Diameter
4.8 mm (3/16 in.)
6.35 mm (1/4 in.)
Figure 2. Maximum Immersion Depth
Table 2. Time Constant
14 seconds
21 seconds
Time Constant
Stik Thermometer
Operation
gjo002.bmp
5