Product specifications

Instrumentation Laboratory Exercise 18
2.4 Calibration procedure
We will perform a “two- point” calibration of the diode temperature
sensor. To calibrate the sensor you will need a small amount of ice.
Power up the circuit and display the voltage V
D
in an AlphaNumeric
box (found in the Display menu).
Allow the ice to come in contact with the diode and measure the
steady state voltage. You should notice that the diode voltage goes up
slightly when the ice is in contact with the diode. This should only
take a few seconds. Record this voltage as the “zero reference”, V
z
.
Now remove the ice and allow the diode to warm up to the room
temperature. Measure the room temperature using the room
thermometer. In the absence of a thermometer you may assume the
room is at 25 °C. Record the steady state voltage, V
r
of the diode
when it is at room temperature.
The calibration factor may now be calculated through:
Where T
room
is the temperature of the room in °C, and T
ice
is 0 °C.
The formula for converting the diode junction voltage to °C is then:
Using the actual numbers (approximately 0.7 V for V
z
and ∼1000 for
CalFact) fill out a formula box to perform the conversion. It should
contain a formula like:
Where A is the voltage of the diode entering the formula box, and
0.692 is replaced by your 0 °C diode voltage.
CalFact T
room
T
ice
–()V
r
V
z
–()⁄=
CalFact V
D
V
Z
–()×
1000– A 0.692–()×