| 摘要 |
<p>The invention concerns the control of a furnace partic. in heating a sample from T1 degrees C to T2 degrees C in time to and maintaining it at T2 degrees C for time t1. The control is numerical and the appts. incorporates an oscillator, a frequency divider, a binary counter, a numerical analogue converter, a thermocouple and pyrometer, a comparator and a clock circuit. The frequency divider is connected to the output of the oscillator and to te controller of the N module of the divider. It delivers an output of impulses at frequency f/N, where f is the frequency of the oscillator. The input of the binary counter is connected to the output of the divider and to a stop and return to zero logic. The counter delivers a numerical electrical signal proportional to the total number of impulses delivered by the divider. The numerical signal is fed to the numerical analogue converter which delivers an analogue signal controlling the power circuit feeding the heating resistance of the furnace. The thermocouple transmits a signal, proportional to the temp., to the comparator, which compares it to a reference value corresponding to the temp. level T2 and delivers an output signal to the stop and return to zero logic of the binary counter. The clock circuit, started by the comparator output signal, delivers, after time t1, a return to zero signal to the stop logic of the counter. The appts. is used in measuring the dose of gamma radiation and/or neutron radiation absorbed by a crystalline sample, by heating the crystal in a furnace and estimating the electrons liberated. The estimation is carried out by e.g. a windowless gas-circulation Geiger-Muller counter. The invention enables the achievement of a linear, precise and reproducible temp. rise and an adjustable closely controlled level period. The method is easier to operate, less costly and less subject to drift than existing methods using e.g. integrated circuits.</p> |
