9
Calibration Procedure
9.1
Single Point Calibration
For a quick calibration to a single point, R
0
may be adjusted by itself without
any calculations. If the system is reading high, adjust R
0
in the calibration
menu higher by small increments until the temperature of the system is correct.
NOTE:
This method may cause other temperature settings to be off by a
degree or two.
9.2
Three 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. Choose three set-points to use in the calibration of the R
0
, ALPHA, and
DELTA parameters.
2. Set the controller to the low set-point. When the calibrator reaches the
set-point and is stable, wait 15 minutes or so and then take a reading from the
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 other two set-points recording them as T
2
, R
2
, T
3
, and
R
3
respectively.
4. Using the recorded data, calculate new values for R
0
, ALPHA, and DELTA
parameters using the equations given below:
9.2.1
Compute DELTA:
A
T
T
=
−
3
2
B
T
T
=
−
2
1
C
T
T
T
T
= ⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦⎥
− ⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦
3
3
2
2
100
1
100
100
1
100
⎥
D
T
T
T
T
= ⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦⎥
− ⎡
⎣⎢
⎤
⎦⎥
−
⎡
⎣⎢
⎤
⎦
2
2
1
1
100
1
100
100
1
100
⎥
E
R
R
=
−
3
2
41
9 Calibration Procedure
Single Point Calibration
