BULGAiIIAN ACADEMY OF SCIENCES
SPACE RESEARCH IN BULGARIA, 3
Sofia ' I9B0
Current-Voltage lNonampere J'ransformer
with Automatic Switching
of the Measurement Qange
M. N. Gousheua
The need to measure curre.nt variaiions within a large dynamic range in space
probe experiments should be matched by reliability (nraximum simplicity of
the equipment) and by inforrnation restriction (minimum number of telemetric
channels used). The switching of the sensifivity scales of the DC measuring
tract of the spaceborn service equipment when the rocket attains a definite al-
tiiude involves a certain hazard. Such switching at an inappropriate moment
results in loss oi useful information due to insufiicient dynamic range oi the
electron block.
That is why it is necessary to switch the range in accordance with the
conqrete siiuation (charge carriers density in space plasma) [1], The availabi-
Iity ol only one channelprovidinginformatior as well as two sensitivity scales
covering a dynamic range of 103 (in case of measurements with meteoro-
logical rockets) imposes certain restrictions on the transformer design.
The block circuit of the DC measuring tract (current-voltage transformer,
Fig, l) satisfies the above requirerhents. The circuit consists of a DC ampli-
fier (DC\), a comparator (C), a repeater (R), and a switching device (S). When
collector current from a spherical ion trap is applied to the DCA input, it is
transformed into U, voltage and enters the telemetric channel (TMS). The en-
tire DCA divider is switclred on at the initial moment, because the range has
to be selected regardless of the magnitude of the input current. U"r:-10 V
is applied to the non-inverting input of C. The electron keys are in the follow-
ing positions: I{r-open, Kr-closed, and Kr-open. The three possible ca-
ses under these conditions are: (1) The V-A characteristics is entirely describ-
ed within the sensitive scale (Fig" 2 _. sector ar). This sector corresponds to
a region of very low densities. The DCA range is not srvitched. (2) The V"A
characteristics is described both within the sensitive and the coarse scales due
to the sensitive scale saturation at a given moment (Fig. 2 sector &1). This
is the case of high-density measurements, At Ut:- 10 V -(saturation of the
sensitive scale), C is actuated and S sets the keys as iollows: key 1 -- closed
(the DCA coefficient of amplification decreases ten times), key 2
key 3 - open,
elosed (U,z: -0,5 V). (3) The V-A characteristics is fully described
-
Dd
R2
o3
R.r
64
I
I'
\o N
N
N
I'oX
N
r
N
-lN
+i
h0
bc
witbin the coarse scale (Fig. 2 -- sector cl). This is the region of highest den-
sities; C is actuated at the very moment of describing thJcharacterjstics. The
positions of-the.keys.are as- in 6. alter reswitching oithe range. l, is the time
of range selection. FigLrre 2 shows the V-A characteristics ioi one sweep pe-
riod T:1 s of the linearly changing voltage applied to the outer grid of the
spherical ion trap (sectors a,, bn and c, in the 3arne Figure)
_
- Ur."
F'igureB shows theblock electric cilcuitry of the device. MA 740 is used as
an input step with static input resistance oi 1012 ohms, because currents of
the order of X . 10-10 A are occasionally applied to the DcA input. A precise
coeff icient of division in the DCA feedbaek'is obtainecl by tunirig tfre diviOe],
ISr transfornT 4 inlo ur, which enters ihrough the telemetric ch'annel (TMS),
IS_, controls S ansistor Tr), and s controls ttre electroi keyi
'(194)
-- DG 182 with the charge carriers ciensity, as well as
U", and U,r_o input o{ C. T'he onboarcl supply is stabilized
(transistors Tt, be noted in this ca,se that irreie ls no seDa-
rate channel to indicate the operating sensity range. This information is obtain-
ed from the cocperating thresholds L,, aid uu of c over the v-A charac-
teristics.
Thc circuitry ha_s b_een designed and tested at the Central L.aboratory for
^
Space Qesearch of the Bulgarian Academv of Sciences.
Reference
l. S. K. Clrapkunov.*Compt. rend. Acad. bulg. sci.,79, 1916, 12.
HaHoavnepHbrr? npeo6paBoBareJrb roK HarrpflE(eHlre
-
-c aBToMarr4qecKr4M nepeKJrloqeHHeM r.r3Mepl{Te/rbHofo AHar]a3oHa
M. H. I-yweaa "
(Pesrcue)
3oHAonufi Mero.[, IxHpol(o tlpnMeiserce nprl 14ccne,u, olar]r4ri napaMerpoB rJragMbr
c IloMolqbro paKer H cnyrHuxon. B coo6ureusz yr{a3btBaercs ireo6xo,u,uMocrb
II3MepeHl'i8 as[4eneHIrft Toxa B Ixl4pol(oM ,qI4HaMr{qecKoM ,rl,uar]a3oHe. lloxasaHbl
oco6eusocu{ gKcirepr,rMeHTa_npil r{sMefleHHrx Ha Mereopo;loruqecroft parere. B
cBqSIi c 3T?rM co3,4aH npeoSpasoBareJrb AJrs noJryqeuun xaparrepvcruflLl 3oHAO-
Boro roKa. Paccrr,lorpeubl crpyKTypHafl r4 npr4Hqr{nlrarbHas cxeMbr c aBToMarH-
qecKI4M nepeKfiroqeqaeM H3Mepr,ITeIbHOrO
Aliana3oHa.
