Average temperature measurement with MRT
___________________________________________________________________________
Instruction manual VITO
Page 20
3
Average temperature measurement with MRT
3.1
Introduction MRT
An MRT (Multiple Resistance Thermometer) or Variable Length Thermometer comprises a number of resistance
elements of different lengths, all starting close to the bottom end of the temperature probe. Refer to figure 3.1. To
measure the average product temperature, the longest fully submersed element is automatically selected and its
temperature measured.
The average gas temperature is calculated by measuring the temperature of the longest resistance thermometer
element and subtracting the contribution of the average product temperature.
The 762 VITO MRT Interface is used for interfacing an MRT. This unit is basically a solid state electronic element
selector, containing all hardware necessary for selecting and measuring an MRT with up to 13 temperature
elements with one spot element.
The operational board located in the 854 level gauge, 877 FDI or 97x radar, selects the longest submerged
element for the average product temperature calculation.
There is a fixed table with element lengths (see figure 3.1), which are used with the Honeywell Enraf MRT’s. If
another make of MRT is used with different element lengths, then these element lengths are to be entered in a
separate table (refer to the description of items
J0
–
JD
and item
MJ
).
Figure 3.1 MRT tank and probe data
Summary of Contents for Enraf VITO
Page 2: ......
