Technical Data - Intab PC-Logger 3100i How To Use Manual

3.2.3 Three-Wire Resistance Measurements
This method is a poor version of the five-wire method. Its only excuse is that it
only needs three wires to the sensor. (It must not be mistaken for the three-wire
bridge method that is not dealt with in this manual). This method requires the
lead resistances to be either compensated for by calibration or unimportant
enough to be disregarded. They will otherwise contribute to a considerable
measurement error.
This is how you go about connecting the three wires. Compare this to the five
wire method!
(Pt-100)
Use ordinary high school maths and Pt-100 tables to convert measured voltage
into temperature. Apply the best fit straight line (equation) transform to the
temperature range that is to be recorded. This will give best and most accurate
readings.
4

TECHNICAL DATA

At 25°C and nominal current 500µA (other ranges on request)
Constant Current
Accuracy
Compliance
Tempco (max)
44
I
R1
INTAB Interface-Teknik AB
Constant Current
0.500mA
Constant Current
0.500mA
+
U=R1*I-R2*I
-
R2
(100)
GND
AAC-2
500µA
+/-0.5µA
2.5V (0≤RL≤5kΩ)
+/-150ppm/°C