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Bulk micromachined Pirani gauges were designed and fabricated using an H-shaped 1 μm thick silicon nitride support structure and 30 nm of Ni for the meander resistors and connecting metal lines. The distance d between the resistor element and the cold junction was chosen to be 1200 μm. From theoretical and experimental considerations, it is shown that pressures below 10-4 Torr can be measured if the thermal resistances of the two metal lines which connect the resistor element to the cold junction and the thermal support structures are about or larger than 1×106 K/W. Also, the distance d between the resistor element and the cold junction needs to be near or larger than 1000 μm.