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THERMOELECTRIC HEAT FLUX SENSORS

Page 26 of 36

Se = 100 μV/(W/m

Sa = 0.32 V/W

dS/dT=0.2%/°C

To = 27°C

The temperature correction factors are the following:

With use of averaged dS/dT (=0.2%/°C)

��(��) = 1 +

∂S

∂T

× (�� − ��0) = 1 + 0.2 × (50 − 27) = 1 + 4.6%

= 1,046

(9.7)

More precise correction by polynomial expression (9.2) with given

coefficients (table 9.1) gives the following:

��(��) = [(A2 × (�� − ��0 )2 + A1 × (�� − ��0) + A0)]

= [−1,634 × 10−5 × 232 + 1,937 × 10−3 × 23

+ 1] = [−0.00864386 + 0.04455 + 1] = 1,036

(9.8)

The polynomial expression gives a more precise correction factor which is

slightly differing from the rough averaged value.

Thus, if possible, we recommend using the Polynomial expression rather

than an averaged value given in the Specification only as a indicator value.

But for rough estimations the averaged value

∂S

∂T

is quite enough.

8.2 Heat flux measurements

The DX8140 Datalogger, a voltmeter, or a third party read-out device

measures and stores (Datalogger) an analog output in voltage units U (V,

mV, V) .

The heat flux P is calculated with use of sensitivity and calculated

correction factor (theabove section) F(T). Depending on the sensitivity

units V/(W/m

2) (Se) or V/W (Sa) the density of heat flux W/m2 (Ps) or

total heat flux W (Sa) will be calculated as

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