10
Calibration Procedure
CAUTION:
The vertical gradient needs to be checked before calibrating
the furnace. Checking the vertical gradient insures that the sodium
heat-pipe is working properly.
CAUTION:
DO NOT change the value of the calibration parameter
Delta. Delta is set to at the factory (to the value of 1.6) for optimum per-
formance of the furnace.
The user may want to calibrate the furnace to improve the temperature set-point
accuracy. Calibration is done by adjusting the controller probe calibration con-
stants R0 and ALPHA so that the temperature of the furnace as measured with
a standard thermometer agrees more closely with the set-point. The thermome-
ter used must be able to measure the well temperature with higher accuracy
than the desired accuracy of the furnace.
10.1
Two Point Calibration Procedure
In some instances the user may want to calibrate the controller to improve the
temperature set-point accuracy. Calibration is done by adjusting the controller
probe calibration constants R
0
and ALPHA so that the process temperature, as
measured with a standard thermometer, agrees more closely with the set-point.
The thermometer used must be able to measure the temperature with higher ac-
curacy than the desired accuracy of the system.
1. The two set-points that should be used for the calibration are 800°C and
1060°C, since they are used at the factory to calibrate the furnace.
2. Set the controller to the low set-point. When the calibrator reaches the
set-point and is stable (< 0.1°C change in 15 minutes), take a reading from the
reference thermometer. Sample the set-point resistance by holding down the
SET key and pressing the DOWN key. Write these values down as T
1
and R
1
respectively.
3. Repeat step 2 for the second set-point recording it as T
2
and R
2
.
4. Using the recorded data, calculate new values for R
0
and ALPHA parameters
using the equations given below:
10.1.1
Compute R
0
& ALPHA:
a
T
T
T
1
1
1
1
1 6
100
1
100
=
+
⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦⎥
.
a
T
T
T
2
2
2
2
1 6
100
1
100
=
+
⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦⎥
.
71
10 Calibration Procedure
Two Point Calibration Procedure
