HP 3478A Technical Manual page 106

3478A 3478A
slopes. For a perfect zero slopes. For a perfect zero reading, the number
slopes will be the same as the number of S-4 slopes. slopes will be the same as the number of S-4 slopes.
This is represented in Figure 7-F-10. This is represented in Figure 7-F-10.
7-F-38. 7-F-38. Slope S + Slope S + 4 and S-4 4 and S-4 Generation.
explains how the curents for slopes S+4 and S-4 are explains how the curents for slopes S+4 and S-4 are
generated. generated.
a a . . S S lo lop p e e S S + + 4 4 . . Refer to Refer to Figure 7-F-I
both Y1 both Y1 and Y2 pat and Y2 paths are connected hs are connected to ground.
the summing node of the paths is a virtual ground and the summing node of the paths is a virtual ground and
Y1 and Y2 are also connected to ground, no current Y1 and Y2 are also connected to ground, no current
flows between the paths and the summing node. flows between the paths and the summing node.
Current does flow from + Vref (Positive Reference Current does flow from + Vref (Positive Reference
Voltage) through a 100K ohm resistor into the integrator Voltage) through a 100K ohm resistor into the integrator
capacitor (con- nected to the negative terminal of U401). capacitor (con- nected to the negative terminal of U401).
This generates a negative going output slope. This generates a negative going output slope.
b b . . S S lo lop p e e S S - - 4 4 . . Refer t Refer to Figure 7-F-12.
both Y1 and Y2 paths are connected to -Vref (Negative both Y1 and Y2 paths are connected to -Vref (Negative
Reference Voltage). Reference Voltage). Since the summing node Since the summing node is a virtual
ground, current flows from + Vref through a 100K ohm ground, current flows from + Vref through a 100K ohm
Figure 7-F-11. Figure 7-F- 11. Slope S+4
Figure 7-F-10. Figure 7-F-10. Runup Slopes for Zero
reading, the number of S + 4
Generation. The following The following
Figure 7-F-I I. I. Note that Note that
to ground. Since
o Figure 7-F-12. Note Note that
is a virtual
Slope S+4 Generation Generation
Runup Slopes for Zero Inputs (41/2
Digit Model) Digit Model)
of S + 4 resistor and paths Y1 and Y resistor and pat
from the integrator capacitor (C) from the integra
generated because the total resistance of the Y1 and Y2 generated because the total resistance of the Y1 and Y2
paths is smaller than the 100K ohm resistor from + Vref. paths is smaller than the 100K ohm resistor from + Vref.
The current from + Vref plus the current from the The current from + Vref plus the current from the
capacitor equals the total current through paths Y1 and capacitor equals the total current through paths Y1 and
Y2. Y2. Since the total resistan Since the total resistance of paths Y1 and Y2 is 50K
ohms, the current from + Vref (II) and the current from ohms, the current from + Vref (II) and the current from
Since
the capacitor (I2) is half as large as the total YI and Y2 the capacitor (I2) is half as large as the total YI and Y2
current (13). The resultant output current (13).
that
7-F-39. Slope S 7-F-39.
Figure 7-F-13. Figure 7-
resistor (YI path) is connected to ground and the other resistor (YI path) is connected to ground and the other
side is side is con- necte
100K ohm resistor from +Vref (Y3 path) and the IOOK 100K ohm resistor from +Vref (Y3 path) and the IOOK
ohm resistor from -Vref (Y2 path) are also connected to ohm resistor from -Vref (Y2 path) are also connected to
the summing node, no current flows from the integrator the summing node, no current flows from the integrator
capacitor (C). This is because capacitor (C).
path Y2 and Y3 is the same and makes the current value path Y2 and Y3 is the same and makes the current value
of paths Y2 and Y3 the same (but opposite polarity). of paths Y2 and Y3 the same (but opposite polarity).
This is true for both slopes S + 0 an This is true for
7-F-12 7-F-12
Inputs (41/2
hs Y1 and Y2 to -Vref. 2 to -Vref. Current also flows
tor capacitor (C) to -Vref.
ce of paths Y1 and Y2 is 50K
The resultant output slope is positive.
Figure 7-F-12. Figure 7- F-12. Slop S-4 Slop S-4 Generation
Slope S + 0 + 0 and S-O and S-O Generation.
F-13. Note that one side Note that one side of a
con- nected to d to the summing n the summing node.
This is because the resistance
both slopes S + 0 and S-0.
TM 11-6625-3071-14 TM 11-6625-3071-14
Current also flows
to -Vref. This current is This current is
slope is positive.
Generation
Generation. Refer to Refer to
of a IOOK ohm IOOK ohm
ode. Since the Since the
the resistance value of value of
d S-0. The only dif- The only dif-