| 摘要 |
<p>PURPOSE:To lower the spatial resolution of a hot-wire current meter and, at the same time, to make the adjusting and calibrating work of the current meter easier by periodically switching the steady temperature of a thermo-sensitive sensor and detecting the velocity of a current on the basis of the difference in diffused quantity of heat. CONSTITUTION:A bridge circuit 10 is constituted of fixed resistors R1 and R2, a thermo- sensitive sensor, namely, platinum sensor 1, and a serially connected body of fixed resistors R and (r) and is maintained in a steady state by feeding back the voltage variation across its terminals by means of an amplifier 3. The contact 11a of a relay 11 is connected to one side of the circuit 10 and the fixed resistor (r) is short-circuited with the circuit 10 in accordance with a signal. The voltages across both ends of the resistor R1 and across both ends of the sensor 1 are supplied to an arithmetic processing circuit 14 after they are respectively converted into digital signals by means of A/D converters 12 and 13. The circuit 14 detects the steady state of the circuit 10 and, when the circuit 10 reaches the steady state, switches the relay 11 and, at the same, calculates the diffused quantity of heat Q and detects the velocity U of a current on the basis of the difference between diffused quantities of heat Q1 and Q2 at different steady temperatures T1 and T2 and displays the velocity U on a display 15. Q1-Q2=(a+bU<1/2>) (T1-T2), where (a) and (b) are constants.</p> |
