Teledyne BDS-3960 - Oxygen analyzer - Manual (Page 46)

Maintenance BDS 3960
Teledyne Analytical Instruments 46
Figure 4.2: Parameter Selection Box
4.3.2.1 T HE D IGITAL F ILTER
The Analyzer software performs a digital operation to reduce the
noise from the BDS sensor and amplifier. This filtering is reduced to
around 10 ppb. If the signal exceeds 10 ppb, the filter disengages in
order to track the transient faster. The number approximately
corresponds to the response time of the filter in minutes from 10 to 90
%. The range is from 1 to 60 minutes of the 90 % response time. Five
minutes is the default.
4.3.2.2 The Gas Factor
The gas factor coefficient in the BDS 3960 is the ratio of the output
of the sensor taken in a N
2
background over the output of the sensor in
the new background gas. The output of the sensor depends on the
mechanics of diffusion. Since the diffusion coefficient of oxygen
depends on the viscosity of the background gas, according to the laws of
diffusion, the output of the sensor becomes inversely proportional to the
viscosity of the background gas.
The output of the sensor can be predicted by looking up the
viscosity of the new background gas and compare it to the viscosity of
N
2
at the same temperature. Using values obtained from the a science
handbook, the following gas factor coefficients for the BDS sensors are
calculated
Table 4-1: Gas Factor for Selected Gases
N2 = 1*
H2= 1.99
He= 0.90
Ar= 0.79
Select Factor to Adjust
Filter Gas Factor
Tmp. Coeff.