Fluke 9116A User Manual page 77

opening. The fiber ceramic insulation provided may be added or removed
to do this. Generally the bottom position must be filled and additional
spaces above may be filled as required.
• Check of the Controller Set-point Accuracy: This test is carried out in
a metal freeze point cell where the metal has been completely melted.
Prepare the furnace in the same fashion as though a freeze plateau would
be conducted up to the point that the metal sample is melted. This exam-
ple illustrates measurements made near the silver point:
♦
Set the temperature of the furnace at 964°C and allow it to stabilize as
would be done in preparation for a freeze. Measure the EMF of a ther-
mocouple inserted into the cell. Compare the measured EMF to one
taken at the M.P. or F.P. The actual temperature, t, in the cell can be
calculated by using the following equation:
E
= ° +
1
t 961 78 . C
0 0114 .
where E is the measurement EMF and E
1
the M.P. temperature of copper for this example) and 0.0114mV/°C is the sen-
sitivity of a Type S thermocouple near the M.P. of silver.
For example, the measured EMF E
E =9.1481 mV, the actual temperature in the furnace.
0
−
91502 91481 .
t = +
961 78 .
0 0114 .
Since t=964.0°C = the actual set-point, the error, if any, is very small. If the er-
ror is larger than 1°C, you can make an adjustment to the set-point.
−
E
0
°
mV C
is the EMF at the M.P. (961.78°C is
0
=9.1502 mV, the EMF at the M.P.
1
.
= °
961 96 . C
75