7.3 Setting the Temperature
Section 8.3 explainsin detail how to set the temperature set-point on the cali-
brator using the frontpanel keys. The procedure is summarized here.
(1) Press “SET” twice to access the set-point value.
(2) Press “UP” or “DOWN” to change the set-point value.
(3) Press “SET” to program in the new set-point.
(4) Press “EXIT” to return to the temperature display.
When the set-pointtemperature is changed the controller will switch the well
heater on or offto raise or lower the temperature. The cycle indicator, a two
color LED, willalso indicate on (red and heating) or off (green and cooling).
The displayed well temperature will gradually change until it reaches the
set-point temperature. Thewell may require 5 to 20 minutes to reach the
set-pointdepending on the span. Another 5 to 10 minutes is required for the
temperature to stabilize.
7.4 Calibrating Probes
The dry-well block providesa constant temperature environment in which
probes may be compared.The probes inserted into the block may be compared
to the welltemperature displayed on the front panel of the calibrator. The
probes should be insertedthe full depth of the well since the temperature at the
bottom of the well will most closely agree with the displayed temperature.
Forgreater accuracy the probes may be compared to a referen cethermometer
inserted intothe block. The reference thermometer may be inserted into one
hole while the probes to be calibrated are inserted into another. The drawback
to this method is that because of temperature variationsthroughout the block
there may be a smalltemperature difference between one hole and another
which can cause errors.
Using the same hole for the reference thermometer and the test probe may have
betterresults. This however requires switching the probes which takes more
time.One must allow a few minutes after inserting the probes for the tempera-
ture to stabilize before making measurements. Because of temperature varia-
tionsalong the length of the well, best results are obtained when comparing
probes of similarconstruction and inserting them the same depth into the well.
22 HartScientific
7General Operation