To calibrate our relative microbarometers ( models: BMG
and Schott ) we operate a
Paroscientific Model 740 Microbarometer.
While our permanently recorded microbarometers are installed deep inside
the mountain (next to the electronics chamber for WDO and in the tilt
meter chamber for WDI) we noticed that WDO is adversely affected by the
wind draft in that part of the mine which is in front of the pressure
lock. Since the WDO channel is used for the barometric pressure correction
we attempt to eliminate the dynamic pressure signal (from wind draft) by
installing a pressure compensated microbarometer outside the mine.
Below we present the results of our tests with which we tried to see how good the temperature compenstion of the Paroscientific pressure transducer is.
The Parosci was cyclically heated with a UV lamp. The lamp was on for 30 minutes and off for 90 minutes.
For its temperature compensation the Parosci makes independent temperature and pressure measurements and subsequently compensates the pressure for any temperature changes. Both the temperature and the (compensated) pressure were recorded at one sample every 10 seconds for several weeks. The figure below shows the data in the time domain. The amplitude of the periodic temperature signal was around 4 deg C.
Powerspectral densities of the above two time series are given below. The temperature compensation of the pressure is realized so well that none of the harmonic temperature signal at 0.19 mHz is visible in the pressure.
For seasonal temperature variations which can amount to 30 deg C the temperature compensation of the Parosci should also be sufficient, considering that the pressure background noise increases towards the long periods.
