with \(R\) the gas constant, \(-\,\dot{\!\omega}/\omega\) the relative deceleration rate and \(p_\text{cal}\) the calibration pressure generated by the primary standard. For the calibration with the measurement gas nitrogen the extrapolated effective accommodation coefficient \(\sigma_0\) for \(p < \SI{1E-2}{\pascal}\) was: \[\sigma_0=\lim_{p_\text{cal}\rightarrow0}\sigma(p_\text{cal})=\SI{0.9555}{}\quad(\text{nitrogen})\] With this \(\sigma_0\) together with \(d\) and \(\rho\) from the parameter set under section \ref{sec:procedure}, the SRG controller will give the correct reading of pressure within the measurement uncertainties according to this calibration for pressures \(p < \SI{1E-2}{\pascal}\). Alternatively, the pressure can be calculated from the relative deceleration rate according to \[ p_\text{ind}=\frac{\pi\rho d}{20\sigma_0}\sqrt{\frac{8 R T}{\pi M}}\left(-\frac{\dot{\!\omega}}{\!\omega}-\text{RD}(\omega)\right)\,. \] In both cases offset and temperature have to be determined for each measurement.\par In the pressure range \(p > \SI{1E-2}{\pascal}\) up to \(p =\SI{2}{\pascal}\), the real pressure \(p\) will be received by multiplication of the indicated pressure \(p_{\text{ind}}\) with a correction factor \(f(p_{\text{ind}})\): \[ p = p_{\text{ind}} f(p_{\text{ind}})\] and viscosity = 0 entered in the controller. From our calibration, \(f(p_{\text{ind}})\) was obtained for this rotor by the following equation: \[ f(p_{\text{ind}})=(1+(\SI{0.01796+-0.0006}{\per\pascal})\cdot p_{\text{ind}})\quad(\text{nitrogen})\]
with \(R\) the gas constant, \(-\,\dot{\omega}/\omega\) the relative deceleration rate and \(p_\text{cal}\) the calibration pressure generated by the primary standard. For the calibration with the measurement gas nitrogen the extrapolated effective accommodation coefficient \(\sigma_0\) for \(p < \SI{1E-2}{\pascal}\) was: \[\sigma_0=\lim_{p_\text{cal}\rightarrow0}\sigma(p_\text{cal})=\SI{0.9555}{}\quad(\text{nitrogen})\] With this \(\sigma_0\) together with \(d\) and \(\rho\) from the parameter set under section \ref{sec:procedure}, the SRG controller will give the correct reading of pressure within the measurement uncertainties according to this calibration for pressures \(p < \SI{1E-2}{\pascal}\). Alternatively, the pressure can be calculated from the relative deceleration rate according to \[ p_\text{ind}=\frac{\pi\rho d}{20\sigma_0}\sqrt{\frac{8 R T}{\pi M}}\left(-\frac{\dot{\!\omega}}{\!\omega}-\text{RD}(\omega)\right)\,. \] In both cases offset and temperature have to be determined for each measurement.\par In the pressure range \(p > \SI{1E-2}{\pascal}\) up to \(p =\SI{2}{\pascal}\), the real pressure \(p\) will be received by multiplication of the indicated pressure \(p_{\text{ind}}\) with a correction factor \(f(p_{\text{ind}})\): \[ p = p_{\text{ind}} f(p_{\text{ind}})\] and viscosity = 0 entered in the controller. From our calibration, \(f(p_{\text{ind}})\) was obtained for this rotor by the following equation: \[ f(p_{\text{ind}})=(1+(\SI{0.01796+-0.0006}{\per\pascal})\cdot p_{\text{ind}})\quad(\text{nitrogen})\]
