7.9.8 Prb Type
This functionspecifies the type of probe and its characterization. It allows the
instrumentto use the appropriate algorithm to calculate temperature from the
measured resistance of the probe. The functionsthat follow the probe conver-
sion function for setting probe characterization coefficients depend on the se-
lectedprobe type. The table below lists the probe types and the corresponding
coefficients.
ProbeType Description Coefficients
ITS-90 PRTscalibrated to ITS-90 R(.01),a, b, c, d, a4, and b4
IEC751 PRTs(RTDs) conforming to IEC-751 none
CVD PRTscharacterized by the
Callendar-VanDusen equation
R0,Alpha, Delta, and Beta
YSI-400 Thermistorsmatching the YSI-400 series none
THERM Thermistorscharacterized by the therm-
istorpolynomial
b0,b1, b2, and b3
Each of theconversion options is explained in the following sections along
with their associated coefficients,when applicable. The probe type and associ-
ated coefficientsare stored in the INFO-CON probe connector. Use the Up and
Downbuttons to select the probe type and the ENT button to store and
continue.
Each of the coefficientsthat follow the probe type are set in the usual way. Use
the Up and Downbuttons to set each digit and the ENT button to move to the
nextdigit to the right. Press ENT when all digits are entered.
7.9.9 ITS-90
The ITS-90 typeis for PRTs calibrated and characterized using the Interna-
tionalTemperature Scale of 1990 equations. Probes that use this linearization
curvegenerally have excellent accuracy (0.005 to 0.025°C), a wide operating
range (–180°C to 420°C or higher). The coefficientsthat appear when ITS-90
is selected are “R(.01)”, “a”, “b”, “c”, “d”, “a4", and ”b4".These should be set
to the coefficientvalues that appear on the PRT calibration certificate according
to the following table.
Allcoefficients, except R(.01), have values greater than or equal to –1 and less
than or equal to +1,i.e. –1 ≤va lue ≤+1. The instrument does not allow values
outsidethis range to be entered. If a value less than –1 is entered, the coeffi-
cient defaults to –1. If a value greater than +1 is entered, the coefficient defaults
to +1.
Unused coefficientsmust be set to 0.
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7 Display Functions
CAL MODE