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7012 Calibration Bath
User's Guide
11.3
11.4
60
the bath was set for 80°C and the thermometer measured 80.1°C giving an error
of +0.1°C.
Computing D0 and DG
Before computing the new values for D0 and DG the current values must be
known. The values may be found by either accessing the probe calibration
menu from the controller panel or by inquiring through the digital interface.
The user should keep a record of these values in case they may need to be re-
stored in the future. The new values DO' and DG' are computed by entering the
old values for DO and DG, the calibration temperature set-points t
the temperature errors err
−
err t
(
D
0
)
' =
L
H
D
0
t
H
⎡
−
err
err
' =
H
L
DG
⎢
−
⎣
t
t
H
L
If for example D0 and DG were previously set for –25.229 and 186.9740 re-
spectively and the data for t
new values D0' and DG' would be computed as –25.831 and 188.220 respec-
tively. Program the new values D0 and DG into the controller. The new con-
stants will be used the next time the bath temperature is set. Check the
calibration by setting the temperature to t
again. If desired the calibration procedure may be repeated again to further im-
prove 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 current val-
ues for D0 and DG are –25.229 and 186.974 respectively. The calibration
points are chosen to be 25.00 and 75.00°C. The measured bath temperatures are
24.869 and 74.901°C respectively. Refer to Figure 10 for applying the equa-
tions to the example data and computing the new probe constants.
and err
into the following equations,
L
H
−
−
err
(
t
D
0
)
+
H
L
D
0
−
t
L
⎤
+
⎥ 1
DG
⎦
, t
, err
, and err
L
H
L
and t
L
L
were as given above then the
H
and measuring the errors
H
and t
, and
H
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