when all thedigits are correct. If the password is entered correctly the first pa-
rameter inthe menu will appear.
6.4 Selecting the Probe Characterization
Before the 1502A can measure temperature accurately it must knowhow to cal-
culate temperature from the resistance of the sensor.You must select a conver-
sion type and enter thep roper characterizationcoefficients. There are several
temperatureconversion algorithms available. The one to use depends on the
typeof probe you are using and its calibration.The conversion algorithms use
coefficientsthat characterize the sensor. Coefficients are determined when the
probe is calibrated.SPRTs and PRTs often use the ITS-90 algorithms and are
providedwith ITS-90 characterization c oefficients.
6.4.1 Setting the Probe Characterization Type
The probe characterization type and characterization coefficientsare set in the
Probemenu. Press the Menu button (“SEt? ” appears), then the C/Probebut -
ton. The menu name, “ProbE”, will appearbriefly then the characterization
type. The probe characterizationtypes are indicated on the display as follows:
Pr= t90 ITS-90
Pr= rtd Callendar-Van Dusen
Pr= t68 IPTS-68
Select the desired probe characterization type using the Uand Dbuttonsand
pressing the Enter button.After the characterization type is selected the char-
acterizationcoefficients follow. The coefficients that appear depend on the
probe type that wasselected.
6.4.2 Setting the Characterization Coefficients
Probe characterization coefficients are setw ithin the Probemenu after select-
ing the probe characterization type. Each coefficientappears with the name of a
coefficientshown briefly followed by its value. For example,
A4
+4.336079
Forsome coefficients, you only need to set the digits in the number. Other coef-
ficientsalso have a sign as shown above (positive sign appears as “+”). Use the
Land Rbuttons to movebetween the digits (and the sign). The selected
17
6 General Operation
Selecting the Probe Characterization