DE1639288C - Electronic mAs relay of an X-ray diagnostic apparatus - Google Patents

Description

ι 2

The invention relates to an electronic mAs-P.elais circuit measures, however, resulted in one

an X-ray diagnostic apparatus that measures a further enlargement of the difference between

Has capacitor, which is from one to one of the actual value and the target value with increasing mA values

Resistance falling through tube current flowing through it (German Auslegeschrift 1 240 595).

Voltage across a charging resistor and an im 5 In German patent specification 969 301 are the

Charging circuit lying controllable electronic basic considerations when building a

Element is charged and which are to be switched on with a switch mAs relay. To the Kora-

element is connected, which at a given compensation of the measurement error it is known from

The value of the voltage reached at the measuring capacitor to pre-charge the measuring capacitor negatively. For this

triggers a switch-off signal for the X-ray apparatus, but an additional voltage source is loaded

wherein the control electrode of the electronic element necessary, so that the effort for the shown there

with a solution through which an X-ray tube current flows

Compensation resistor is connected so that the case of one of U.S. Pat. No. 2,545,247

Resistance of the element through the mAs relays of the type mentioned at the beginning known on the Kompen-

sation resistance dropping voltage depending on the

ability of the mA value of the X-ray tube current, which is worth knowing, the switched mA

will change. not proportional over the entire measuring range

In known devices, the voltage on the measuring capacitor is in the circuit. With this one of the X-ray tube, preferably in the middle of the known mAs relay, is in the charging circuit of the Kon secondary winding of the transformer feeding the tube is an electron tube, the grid of which is in formator », a resistor switched on, to which dependence on the magnitude of the flowing current in the shunt a resistor and a Kcndsa- is applied. You can with such a. 1 sator, possibly also an electric valve, arrangement for a certain area a Komin Row, whereby the resistances and the compensation achieve, but not for the entire.! Capacitors are dimensioned so that during the »5 measuring range of a mAs relay.

Duty cycle of the X-ray tube of the capacitor mAs relays are already known in which a continuous charge of the measuring coriüe ·.; Kiss occurs in the terminals of the resistor lying in the circuit of an adjustable charge state for switching purposes X-ray tube. Be 30 is used, but in which a running Lada : \ q one draws the X-ray tube current i through and discharge of the capacitor and a count of the resistance with r, the capacitance of the condenser charging process takes place. The number of charges of the capacitor with C, those in series with it until it is switched off, corresponds to the desired!.:
Resistance with R and the. Voltage to which the mAs value. This known circuit is indeed n \: capacitor must be charged in order to set up the electronic components, namely to trigger the activation of the X-ray tube, with c, it is a feedback transistor circuit, which is indicated by ι /.-; ir the voltage at the measuring capacitor, which initially increases in the charging circuit of the capacitor, and the charging time / results is solved and thereby its periodic adjustment from the equation is effected, however, due to the under-

40 different tasks with regard to

.f = R · C · In -''-- = 2.3 · R ■ ■ C log ^'r; present invention different circuits

ir - c ' ir - c' is used (British Patent 1,067,948).

The present invention is based on the object

if you set 2,3R-C = K and multiply from, an electronic mAs relay for an X-ray

to build both sides of the equation with the tube current i, 45 diagnostic apparatus in such a way that the

this gives the following equation for the mAs values set over the entire mA range

Product: also really to be switched.

i _r This task is performed with a mAs relay of the

/ · T = i · K · log _:. initially mentioned type according to the invention thereby

^tr ~ ^c 50 solved that the controllable electronic element one

This amount of electricity must now if the on-transistor is. whose emitter-collector path should work correctly in the direction of the mAs relay, is in the charging circuit of the measuring capacitor and each value of the tube current i has the same value as the base with a bias source and with the, as long as the factor K, i.e. the size Compensation resistor is connected in such a way, the resistor R and the capacitance C of the capacitor 55 that the transistor are not changed by the bias voltage source densiitors. However, this is not the case with small mA values of the X-ray tube current, as one can easily under-open by inserting it and its resistance can be determined as a result of the value of the X-ray tube current with increasing values in the above equation. The result is that if the Span mA values falling at the compensation resistor are small, the actual value increases automatically from the nominal value in the direction of 60 voltage, and deviates from an increase parallel to the emitter. Collector path of the transistor if necessary

Several mAs relay constructions with an adjustable resistor are already provided and the size of the resistor, with the possibility of correcting the actual value, is selected in such a way that it becomes known through it when the Tran setpoint value is blocked. So it is known that the sistor still flows such a large charging current that the parallel to the measuring resistor the series circuit 65 measuring capacitor at high mA values in the pre-compensation resistor and a non-written time for the triggering of the switching linear resistor, the value of which with increasing elements specified charging voltage reached.
Current drops, to be provided. Together with other values, η the formula derived above is used

Claims (1)

1 633 288 3. of / over 10OmA, it can be seen that the down reaches small mA values. At about 100 mA deviation has the actual value from the target value is always the transistor has a very high Widerstanu is "ringer and easily in the normal to-current flows almost completely ^UDC Sssigen scattering range One must therefore the resistance 11. The adjustable ^ ° ^β """~. · To the emitter-collector path of the transistor par- 5 can be set from which mA-weri ui * switched-off resistor in its size so control of the transistor begins, choose that through it with blocked Trasistor In series with the capacitor? Is a "'" at values above 10OmA the specified mAs level 13. The aWauero Values are achieved. Voltage is added to the charging voltage of the In the case of short-term exposures, the response and io capacitor play and together result in the oeuu switch-off time of the switch-off voltage that switches the X-ray exposures. Because of this “a ^η °, contactor” plays a role insofar as it is added to the capacitor charging time that is taken into account for the fall time ae “, and it has a relatively protective effect on short-term recordings. . . has a strong impact on the total time. To this influence In the device 14 a ^nICK J? £ *. to compensate or the result cheaper to 15 pelte transistor circuit which is slowly increasing. ■ "Stalten, is the capacitor" reshaped V between the connection points for the switching element. This pulse is m the ^ "in continuation of the invention, voltage 7 into an S *" ⁸ .. in R.'ihe with the measuring capacitor a resistor of a bistable ^Flip- flop 16 g ^e 8 ebca; p ", .- _en « Uv whose size is chosen so that the aa die-line 17 is the flip-flop 16 after every "^ * ^ r-'resistance falling to the charging voltage of the 20 a defined switching state _{α e} o ^ · V'- · ·· '-i-nsatc "·« aiiHi'ertp «» nanriiing Hj «ßiriicV- Via the output of the flip-flop la is em ^ s ^ i - :: i ^; '- "g""the switch-off delay" triggered at the output 18, which causes the X-ray accuracy of the switch-off signal. This is achieved for switching via the contactor 19 "γ" Ρ ° ι. ! df ^"":: - h for short-term recordings Absc'na;> paii- is to terminals 20, 21 a ¹⁰¹⁵ PJJ ¹ ^ '* _n . '·· .. ■ already after a very short time results that »5 is applied, the _{voltage dropping across the contact 22 <jtnes'' · he a} l" ι resistor is switched on to the relay set. U ^ ■ h ■ - ■ -, '■. ■.-h low charging voltage of the capacitor Relay switches the contacts 23, 24 over -.1 t} ;;; will overshadow. bistable multivibrator given. This gjw * « ^R ™ * £ • 3.- Use of transistors results in a 30 recording free. At the same time u & ~ r - .. ·., Change dft information according to the relay of the contact 25 briefly Gescniosse.i , ^ L -: '- i ^: ' ..! Level of the capacitor. In order to discharge capacitor switching processes and thus for the vigen. > - ^ ■■■ ·· ■■ 'loser., One can, as is well known, gemacn on the Kon X-ray image ready for operation .. 7z ^ λ \ οχ lying voltage of the bias of a By using electronic tiaugutuc. - Counteract V matrons and if 35 is exceeded the Voitestzeit is very short. the ignition voltage through the switched thyratron Patent claims: Switch off the dp X-ray machine. . . X-ray The present solution for an electronic 1. Electronic mAs relay «« J ^ [JJn , -As relay wants to avoid such thyratrons. It diagnostic apparatus that has a ^M ^ J ° ⁿ ° J "[" _n . ί _{! Γ} α therefore further vo / struck that the switching 40, which is indicated by the · »« YYYYY ^ S H _e! , ment to generate the switch-off signal, a tube-current flow meter T.an.istor circuit with feedback .ufweirt .. when falling. ^ "^^ Γ '^ η ^ scares the opening of a transistor only after ÜDer- and an im ^u j ^stro 7 "JJJJ ^ _and the if one of the intended cut-off voltage electronic element ^^^^ ^ ^U _{that occurs} corresponding threshold value takes place. 45 with a ^Sch _u ^Altel ™ \ ^VC. ™ _m ⁿ measuring compl _ond en- The figure shows, purely schematically, a given value ^ jJJ _f [Example shown according to the invention. sator reached tension on the ataduftngna ^ door The distance between points I and 2 is triggered by the X-ray apparatus, ^ ^{1 d} ^ ^ from the rectified X-ray tube.strcm through-electrode of the e ectromic ^ ™ ^ ™ * ^. raft. This distance is usually in the earthed ₅ ° K through which the X-ray tube stream flows Center of the high voltage winding. One in ^ ^η ? ^αί1 ° ^η ΤΉ 'p ^ Lnt through di am Kompen- The resistance lying this distance is the resistance of the EIe ™ nU ^d «.« * ^ « ^a ™ _in V Series connection of a resistor 4 and a sationrv.derstand abf Mm ^ SP * «> n changeable resistance in the form of a tranquility ™? . ^^ "h marked By means of the Spa ^ ungquelk 8 and the Zener period 9 ^ T ^^^^^^ Zm ^ counteracts this constant tension and ^ ^m l ^ £ _n s ^ controls the transistor depending on the X-ray (10) • 'JJ ^ f ^^ gSiktoistteckc des tube power to. This makes a correction in the case of the fact that parallel to the bmitter jv Transistor (S) an optionally adjustable resistor (11) is provided and its size is chosen in such a way that when the transistor (S) is blocked it still has such a large charging current flows that the measuring capacitor (7) at high mA values in the prescribed time for the triggering of the switching element (14) reaches the predetermined charging voltage. 2. Electronic mAs relay according to claim 1, characterized in that between the connection points a resistor (13) for the switching element (14) in series with the measuring capacitor (7) lies, the size of which is selected so that the dropping across this resistor (13) to the charging voltage of the measuring capacitor (7) added voltage taking into account the switch-off delay when the switch-off signal is triggered. 3. Electronic mAs relay according to claim 1 or 2, characterized in that the switching element (14) has a transistor circuit with feedback for generating the switch-off signal, in which the opening of a transistor only after one of the intended cut-off voltage has been exceeded corresponding threshold value takes place. 1 sheet of drawings