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 D0
′
and DG
′
are computed by entering the
old values for D0 and DG, the calibration temperature set-points t
L
and t
H
, and
the temperature errors errL and errH into the following equations,
D
err
t
D
err
t
D
t
t
D
L
H
H
L
H
L
0
0
0
0
′ =
−
−
−
−
+
(
)
(
)
D
err
err
t
t
D
G
H
L
H
L
G
′ =
−
−
+
⎡
⎣
⎢
⎤
⎦
⎥
1
If for example D0 and DG were previously set for –25.229 and err
H
were as
given above then the new values D0
′
and DG
′
would be computed as –25.831
and .0028720 respectively. Program the new values D0 and DG into the con-
troller. The new constants will be used the next time the bath temperature is set.
Check the calibration by setting the temperature to t
L
and t
H
and measuring the
errors again. If desired the calibration procedure may be repeated again to fur-
ther improve the accuracy.
11.4
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 and 75.00°C. The measured bath tempera-
tures are 24.869 and 74.901°C respectively. Refer to
Figure 9
for applying
equations to the example data and computing the new probe constants.
User’s Guide
52
