Scientech H410 Vector Instrukcja Użytkownika Pobierz pdf (Strona 31)

Operation of Astral and Large Aperture Calorimeters with an Analog Chart Recorder:

Note: Whenever a large aperture calorimeter is used without an indicator the interface module is

not used.

Calorimeter Response:

The response of a calorimeter to a single pulse input as displayed by a chart recorder appears below.

The output voltage from a chart recorder can be converted to wattage at any time by:

W = V/S, W

= V

V = Chart recorder voltage level in mV

S = Calorimeter sensitivity in mV/W

The total energy (E) in the pulse can be found by integrating the instantaneous wattage over time:

∞

E = ∫ W(t) dt

The following methods may be used to compute the total integrated energy:

Numerical Integration:

Finding the area under the curve in figure 7 is the equivalent procedure for determining pulse energy. Choose an

appropriate time interval, dt, and perform the summation:

N N

E = ∑ W

xdt = (dt/S)∑ V

I=1 i=1

The error caused by this procedure is:

dE = (dt/S) Σ dV

i=1

The error, in theory, is only dependent upon the value of ∑dV

, that is the cumulative random error of V

. This

number should approach zero if data is carefully taken. The accuracy is also increased if the time interval, dt, is

minimized. Numerical integration can yield accurate results, but is a tedious task.

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Scientech H410 Vector Instrukcja Użytkownika Strona 31