Fluke 1551 EX Руководство по эксплуатации онлайн

1551A Ex/1552A Ex English Instruction Sheet

Page 1

November 2010

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1551A Ex/1552A Ex

Immersion Characteristics

Instruction Sheet

Introduction

The 1551A Ex/1552A Ex Stik Thermometer (Theremometer)

must be adequately immersed in the medium to make an

accurate temperature measurement.

Immersion Depth

The minimum required immersion depth depends on the type of

medium (whether wet or dry) as shown in Table 1. These figures

should result in immersion errors of less than 0.005 °C in most

cases. Actual results can vary depending on the type and form of

the surrounding materials.

Table 1. Immersion Depth

Medium Minimum Immersion Depth

Wet (liquid bath, thermowell with

thermal compound)

7 cm (2.8 in.)

Dry (dry-well, thermowell without

thermal compound)

12 cm (4.8 in.)

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 E 644).The time constant is primarily

dependent on the diameter of the metal sheath of the

Thermometer. Typical approximate time constants are given in

the following table.

Table 2. Time Constant

Sheath Diameter Time Constant

4.8 mm (3/16 in.) 14 seconds

6.35 mm (1/4 in.) 21 seconds