Electrical transmission or interconnection systems – With nonswitching means responsive to external nonelectrical... – Temperature responsive
Patent
1985-05-22
1987-09-15
Miller, Stanley D.
Electrical transmission or interconnection systems
With nonswitching means responsive to external nonelectrical...
Temperature responsive
307595, 328127, 330 9, H03K 513, G06G 718, H03F 102, H03M 100
Patent
active
046942084
DESCRIPTION:
BRIEF SUMMARY
The subject of the invention is a circuit arrangement for the development of a current-impulse converter with variable time constant.
In scientific and technical practice it is very often necessary to process analog signals, e.g. current, digitally in a wide measuring range. There are many types of A/D converters for this purpose. In special cases, e.g. for a thermoluminescent dosimeter evaluation equipment for measuring environmental dose levels or accidental levels, we have to convert the current of the photomultiplier tube--which is proportional to the light of the dosimeter--to digital signals (impulses) in the range of 7-8 orders (from 0.1-1 pA to 1-10 .mu.A).
The current-impulse converter of an ionization chamber type dosimeter is required to work in a similar range. These converters are of complex structure, require more supply voltages, and their power consumption is by no means negligible.
However, with a small, portable, battery fed thermoluminescent dosimeter (TLD) evaluation equipment, a simple structure, high reliability, low power consumption current-impulse converter is required, which can cover 7-8 orders of magnitude with appropriate accuracy.
Hungarian patent description No. 180.858 introduces a current-impulse converter of simple structure like this. It consists of a charging capacitor, a digital gate connected to it, and a feedback means between the capacitor and the output of the gate. The disadvantage of this solution is that the switching speed of the applied active devices--digital gate, feedback means--is limited so the operating range of this current-impulse converter is not more than 5 orders.
The purpose of the invention is to develop a circuit arrangement which retains all the advantages of the above described invention and eliminates most of its disadvantages.
In accordance with this, the task to be solved by this invention is to develope a solution for current-impulse conversion through a measuring range of 7-8 orders.
The invention is based on the principle that by altering the time constant of the current-impulse converter its operating speed is modified and the switching speed of the active elements does not limit it. Therefore if we increase the time constant of the converter at a given operating speed, then--if this step is repeated more--the operating range is expanded by more orders.
The circuit arrangement according to the invention is the improvement of another well-known solution, which has a digital gate, feedback means and charging capacitor, and whose output of the digital gate is connected to the input of the feedback means, and whose input of the digital gate is connected to the charging capacitor and to the output of the feedback means.
The improvement, namely the invention is that this circuit arrangement has at least one control capacitor and serially-connected electronic switch, the other pole/s of the control capacitor/s is/are connected to the input of the digital gate through the input line, the switching input/s of the electronic switch/es is /are connected to control line/s, other input/s of it /them is/are connected to a stabilized voltage line/s.
In the sense of the invention it is practical if the electronic swith is/are transistor/s, reed relay/s or solid state relay/s.
Namely it is practical if the value of the control capacitor/s applied in the invention is 9.times.10.sup.K times more than the value of the charging capacitor, where K is an integer, or one less than an integer power of ten.
Moreover it is practical if the stabilized voltage line/s is/are connected together with the stable voltage line/s.
The invention is presented in more detail by the accompanying drawings, in which we indicate the circuit arrangement according to the invention and its timing diagram.
FIG. 1 is a schematic diagram of the current-impulse converter with variable time constant according to the invention
FIG. 2 is a timing diagram according to the arrangement of FIG. 1.
The structure of the circuit arrangement shown in FIG. 1 is as follows: the 14a-14n control capaci
REFERENCES:
patent: 3497724 (1970-02-01), Harper
patent: 3581300 (1971-05-01), Eloranta
patent: 3783392 (1974-01-01), Drake et al.
patent: 4100515 (1978-07-01), Gupta
Feher Istvan
Szabo Bela
Vagvolgyi Jeno
Davis B. P.
Miller Stanley D.
MTA Kozponti Fizikai Kutato Intezete
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