Scientech Astral Calorimeter - Manual (Page 8)

8
C
ALIBRATION OF
A
STRAL
 C
ALORIMETERS
U
SING
E
LECTRIC
S
UBSTITUTION
H
EATING
:
For Astral calorimeters the electric substitution heating option must be ordered and installed at the factory when
the calorimeter is purchased. It can not be retrofitted to a calorimeter at a later time. To calibrate using electric
substitution heating proceed as follows.
A. Remove the screws holding the calorimeter's ID tag and remove the plate to expose the circuit board.
Figure 4
B. Connect a DVM to the test points labeled SUB and HTR on the calorimeter circuit board.
C. Measure the resistance of the substitution heater making sure to subtract the resistance of the patch
cables from the total resistance measurement. Compare this resistance to Rc in the calibration data in
the front of the manual. The two should agree within 2%. If not contact Scientech.
D. Remove the DVM. Connect a power supply to the SUB and HTR test points and connect the DVM to
monitor the power supply.
E. Connect a second DVM to the output and ground of the Astral calorimeter.
F. Apply Vh volts, stated in the calibration data you received with the calorimeter, to the substitution
heater.
G. Verify that the output voltage is one of the following values depending on the type of calorimeter being
tested:
0.750 volts for 25 mm calorimeters
0.333 volts for 50 mm calorimeters
H. If needed, adjust the calibration trim pot, R4 on the calorimeter circuit board, until the voltage measured
in step G is from the calibration data, is displayed by the indicator.