| 摘要 |
A gas stream detection apparatus having a balanced resistive bridge network enclosed within a housing and an electronic power supply for driving the bridge network. The power supply includes a voltage source feeding a voltage-to-current converter with two differential inputs, a current sensing resistor between the converter and bridge, twin feedback paths to the differential inputs, and a large source resistance connected to the voltage source and in parallel with a smaller source resistance, each connected to separate differential inputs. The resistance R of two bridge filaments increase by DELTA R when exposed to high sample gas concentration causing variations in a current I supplied to the bridge. As DELTA R increases, a bridge output voltage EO decreases. The dependence of current I on DELTA R depends on circuit parameters. The difference between the source resistances permits the voltage source to be non-constant and load dependent. The source output polarity opposes the feedback polarity and under steady state a fixed current I exists. When sample concentration increases, the feedback input decreases causing current I to increase which restores detector sensitivity and provides a linear output voltage response EO.
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