Scientech Astral Calorimeter - Manual (Page 5)

5
Note: Astral calorimeters are sensitive to all types of thermal input. Due to the handling of the
calorimeter during setup and possible environmental temperature differences, thermal gradients
may exist in the calorimeter. Allow the calorimeter to sit undisturbed for several minutes to,
reach thermal equilibrium, before using.
Note: When using a 25mm Astral calorimeter for measuring average power levels below 30mW and
single pulse energy levels below 30mJ, a Scientech Model 36-0203A, Isoperibol Enclosure, is highly
recommended. The isoperibol enclosure should not be used at average power levels above 30mW,
and single pulse energy levels above 100mJ because heat build up will occur.
C
ORRECTING
A
STRAL
 S
ERIES
HD C
ALORIMETERS
O
PERATING
P
ARAMETERS
FOR
U
SE AT
D
IFFERENT
W
AVELENGTHS
:
Scientech Astral calorimeters in general have a flat response to all wavelengths within their specified spectral
response. HD and HDX calorimeters are an exception to that rule and are calibrated at a specific wavelength
by adjusting the calorimeter’s gain circuitry for that wavelength. The calibration wavelength is recorded in the
Operating Parameters section at the front of the manual and on the detector’s serial tag. When a HD or HDX
calorimeter is used at a wavelength other than the calibration wavelength, the calorimeter’s output sensitivity
can be adjusted to compensate for the absorption rate at the new wavelength as follows:
1. Find the absorption rate from the chart at the end of this manual for the calibration wavelength of your
calorimeter.
2. Find the absorption rate for the wavelength where you will be working.
3. Determine the new output sensitivity using the following formula:
absorption rate of calibration wavelength x output sensitivity = output sensitivity for new wavelength
absorption rate of new wavelength from serial tag
NOTE: Due to variability in the manufacturing process the absorption characteristics of the HD model
calorimeters can vary in the UV region (190 to 400nm). Scientech recommends optical
calibration at 266nm if the detector is to be used in the UV region instead of relying on an
absorption rate in the chart at the end of this manual.
C
ALORIMETER
O
PERATION
W
ITHOUT AN
I
NDICATOR
:
Cable Requirements:
Astral calorimeters are powered up by the indicators. To use an Astral calorimeter without a Scientech
indicator, but with a volt meter or chart recorder, you must apply +/-8VDC to the mini DIN connector as shown
in Figure 2. The voltage output of the calorimeter, from pin 8, should be connected to the positive side of the
DVM or chart recorder. All 3 of the grounds should be tied together at the negative side. Pins 2 and 3 are not
used.
Figure 2