Example2:
A thermistorhas coefficients for the equation ln(R) as a function of T given as
a, b, and c. Set the 1521 coefficientsto the certificate values as follows:
1521Coefficients CertificateValue
b0 a
b1 b
b2 0.0
b3 c
7.8.14 Probe Wires
This functionsets the number of connecting wires in the probe. The probe
wires setting isstored in the INFO-CON connector. The 1521 can be used with
probes thath avetwo, three, or four wires. Three wires connecting the probe
sensor instead of twoallows the 1521 to partially cancel measurement error due
to theresistance of the wires. With four wires the 1521 can completely cancel
the error.The internal measurement circuit is configured differently depending
on the number of wires.Important—The 1521 will try to calculate a mea-
surementeven if the wire settings are incorrect. Therefore, the Probe
Wiressetting must match the actual number of wires or loss of accuracy
will result.Use the Up and Down buttons to set the value and press the ENT
button to store and continue.
7.8.15 PCal
This function shows the date the probe was calibrated and allows it to be set.
The dateis stored in the INFO-CON connector and is used simply for refer-
ence. Use the Up and Downbuttons to set each date segment and the ENT but-
ton to moveto th e nextdate segment to the r ight. Press ENT when the date is
correctly entered. Press CLR to moveto the next function without changing the
date.
7.8.16 PDue
This function shows the date the probe is due for calibration and allows it to be
set. The dateis stored in the INFO-CON connector. The probe due date is regu-
larly checkedagainst the present date and if the calibration has expired the user
is alertedwith the message “Prb cal expired”. This message only disappears
when the probe is recalibrated and the probe calibration due date is set to a fu-
ture date. Toset the date, use the Up and Down buttons to set each date seg-
ment and the ENT button to moveto the n extdate segment to the rig ht. Press
ENT when the date is correctly entered. Press CLR to moveto the next func-
tion withoutchanging the date.
35
7 Display Functions
CAL MODE