定電流型ピラニ真空計における大気圧近傍での感度改善

概要

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Rather large errors occur when measuring pressures of around 5×103-104 Pa with a Pirani vacuum gauge in constant current mode, as the change in output voltage is very small. Thus, an attempt was made to achieve more accurate pressure measurement in this range by modifying the thermal conductivity arising from the natural convection flow of gas with the shape of the envelope. The experimental results showed that the pressure range with a large change in output per relative change in pressure expanded to lower pressures when the inner diameter of the envelope increased. For envelopes with an inner diameter of 72 mm, the change |pd V/dp| was greater than 50 mV at pressures from 1.5×103 Pa to atmospheric pressure, while the change |pd V/dp| was less than 20 mV at pressures of less than 2×104 Pa for envelopes with an inner diameter of 34 mm. Thus, more accurate pressure measurement near 104 Pa was achieved with this large envelope.
2011-03-20