Scientech S200 Vector - Manual (Page 18)

Calibration Using Electric Substitution Heating
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.
1
Remove the screws holding the calorimeter’s ID tag and remove the plate to expose the circuit board.
2
Connect the calorimeter to the indicator, turn the power on and let the system equilibrate.
3 Connect theDVM to the test points labeled SUB and HTR on the calorimeter circuit board.
4 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 R
c
in the calibration data in front
of the manual. The two should agree within 2%. If not contact Scientech.
5
Remove the DVM. Connect a power supply to the SUB and HTR test points and connect the DVM to
monitor the power supply.
6
Set up the indicator in Watts Mode and 10 range for 25mm calorimeters or 3 range for 50mm
calorimeters.
7 Apply
V
h
volts in the stated calibration data, to the substitution heater.
8 Adjust the calibration trim pot, R4 on the calorimeter board, until W
h
Watts, from the calibration data, is
displayed on the indicator.
Operation of Astral Calorimeters with a Digital Volt Meter
Astral calorimeters are powered up by the indicator. To use the calorimeter with a digital volt meter or chart
recorder as a read out, you must apply +/- 8 VDC to the calorimeters connector on pins 5 & 4 as show in Fig.
3. The voltage output of the calorimeter is available on pins 6 and 8 as shown below.
* Connect the output of the calorimeter to the DVM using the adaptor cable.
* Select the DC volts mode.
* Direct the laser beam on to the absorbing surface of the calorimeter.
* When the display of the DVM has stabilized (about 1 1/2 minutes), calculate the laser power using
the formula:
W=V/S
where:
W=Laser power in watts
V=Voltage reading of the DVM in mV
S=Sensitivity of the calorimeter which is
0.5 V/W for 25 mm calorimeters and
0.167 V/W for the 50 mm calorimeters.
15