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7060/7061
User's Guide
11.3
11.4
62
Computing R
Before computing the new values for R
be known. The values may be found by either accessing the probe calibra-
tion menu from the controller panel or by inquiring through the digital in-
terface. The user should keep a record of these values in case they may
need to be restored in the future. The new values R
puted by entering the old values for R
ture set-points t
and t
L
following equations,
⎡
−
err t
err t
' =
H
L
L
R
⎢
0
−
⎣
t
t
H
L
⎡
+
(
1
ALPHA t err
' =
ALPHA
⎢
⎣
If for example R
and ALPHA were previously set for 100.000 and
0
0.0038500 respectively and the data for t
above then the new values R
and 0.0038302 respectively. Program the new values R
the controller. Check the calibration by setting the temperature to t
and measuring the errors again. If desired the calibration procedure may be
repeated again to further improve the accuracy.
Calibration Example
The bath is to be used between 25 and 75°C and it is desired to calibrate
the bath as accurately as possible for operation within this range. The cur-
and ALPHA are 100.000 and 0.0038500 respectively. The
rent values for R
0
calibration points are chosen to be 30.00 and 80.00°C. The measured bath
temperatures are 29.843 and 79.914°C respectively. Refer to Figure 10 for
applying equations to the example data and computing the new probe
constants.
and ALPHA
0
and ALPHA the current values must
0
and ALPHA, the calibration tempera-
0
, and the temperature errors err
H
⎤
+
H
ALPHA
1
⎥
R
0
⎦
− +
)
(
1
ALPHA t err
H
L
L
−
t
t
H
L
L
and ALPHA would be computed as 99.885
0
and ALPHA are com-
0
and err
L
⎤
)
+
H
1 ⎥ ALPHA
⎦
, t
, err
, and err
were as given
H
L
H
and ALPHA into
0
into the
H
and t
L
H
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