HP 3478A Technical Manual page 105

3478A 3478A
hypothetical input hypothet ical input value. value.
larger hypothetical input value. larger hypothetical input value.
a. a. When ru When runup s nup star
(C410) is charged by the input current (which is (C410) is charged by the input current (which is
developed by developed by the input the input voltage).
applied to the negative terminal of integrator U401 (see applied to the negative terminal of integrator U401 (see
Figure 7-F-7 Figure 7-F-7), and since the integrator is in the inverting ), and since the integrator is in the inverting
configuration, the resultant output of U401 is positive (for configuration, the resultant output of U401 is positive (for
positive in- put curren positive in- put currents the ts the slope is
capacitor is charged for a short time period. capacitor is charged for a short time period.
b. b. Durin During t g the he time time perio
rent is applied, no other curren rent is applied, no other currents charge C410.
other current is applied to U401 (except the input cur- other current is applied to U401 (except the input cur-
rent), it is called a no current condition and the resultant rent), it is called a no current condition and the resultant
output slope is called slope S + 0. output slope is called slope S + 0.
c. c. After After the the time time perio period, d, a ne
S-4) is th S-4) is then applied en applied to U401. to U401. This current develop
positive going output slope which is called slope S-4. positive going output slope which is called slope S-4.
The S4 current is always the first current applied to the The S4 current is always the first current applied to the
integrator integrator after the after the input current input current is applied.
is applied for 15 ALE cycles (18 ALE cycles in the 50 Hz is applied for 15 ALE cycles (18 ALE cycles in the 50 Hz
option) and is for time period TI. option) and is for time period TI. Since the input
and the applied current in the example have the same and the applied current in the example have the same
polarity, polarity, both charge C4 both charge C410.
opposite polarity, C410 will still be charged in the same opposite polarity, C410 will still be charged in the same
direction but t direction but the output he output slope will be
because the applied current (S-4) is normally larger than because the applied current (S-4) is normally larger than
the input current. the input current.
d. d. Aft After er tim time pe e perio riod TI d TI, cu
no current condition (slope S-O) will then exist for 5 ALE no current condition (slope S-O) will then exist for 5 ALE
cycles (or 6 ALE cycles for the 50Hz option) during time cycles (or 6 ALE cycles for the 50Hz option) during time
period T2. The charge r period T2. The charge rate of Ca
determined by only the input cu determined by o nly the input current.
no current no current condition, condition, as is slope as is slope S + 0.
ference is that the slopes are generated differently (see ference is that the slopes are generated differently (see
paragraph 7-F-39). paragraph 7-F-39). Slope S-O is Slope
previous no current co previous no current condition w
slopes alternate with each other (S + 0, S-O, S + 0, etc.) slopes alternate with each other (S + 0, S-O, S + 0, etc.)
for each no current condition. for each no current condition.
Figure 7-F-9. Runup Slopes (4 ½ Digit Model) Figure 7-F-9.
The dashed lines are The dashed lines are for a
tarts, t ts, the int he integr egrato ator capa r capacit
voltage). The input curr The input current is
slope is negative). negative).
period wh d when o en only nly the the input input cur-
ts charge C410. Since no
a negativ gative cu e current rrent (calle
This current develops a
is applied. The current The current
Since the input cur- rent
10. If the input If the input current was at current was at
slope will be less steep. less steep. This is
, curre rrent nt S-4 S-4 is r is remo emoved
ate of Capacitor C410 is pacitor C410 is again
rrent. Slope S-O is also a Slope S-O is also a
S + 0. The major dif- The major dif-
S-O is selected selected since t since the
ndition was slope as slope S + 0 S + 0. .
Runup Slopes (4 ½ Digit Model)
for a
e. e. When t
applied for 30 ALE cycles (36 ALE cycles for the 50Hz applied for 30 ALE cycles (36 ALE cycles for the 50Hz
citor or option) during option) during time period T3.
same valu same value as
ent is charges C410 in the ot charges C410
discharged and then charged in the other direction). discharged and then charged in the other direction).
Time period T3, and the TS, T7, and T9 periods that Time period T3, and the TS, T7, and T9 periods that
follow are twice as long as time period T1 (30 or 36 ALE follow are twice as long as time period T1 (30 or 36 ALE
The The
cycles instead of 15 or 18 ALE cycles). cycles instead of 15 or 18 ALE cycles).
f. f.
cur-
no current (slope S + 0) no current
Since no
is as long as is as long as time period T2 (5 or 6 ALE cy
also the same time for the S-O or S + 0 slopes that also the same time for the S-O or S + 0 slopes that
follow. follow.
g. g. When T4 i
(called d determines if the outpu determines if
s a crossing occurs when the A/D crossing occurs when the A/D comparator's output (CMP
output at output at U403 pin 11
zero crossing is detected and current S-4 is applied for zero crossing is detected and current S-4 is applied for
time T5 (30 or 36 ALE cycles). time T5 (30 or 36 ALE cycles).
h. h. Aft
cur- rent current current (slope S-O)
crossing was detected (during time T5), current S + 4 is crossing was detected (during time T5), current S + 4 is
applied for time T7, after slope S-0 is completed. applied for time T7, after slope S-0 is completed.
i. i.
This is + 0) is applied + 0) is applied for time T8.
detected, current S + 4 is reapplied for time T9 (after detected, current S + 4 is reapplied for time T9 (after
slope S + 0). slope S + 0).
ved. . A A j. j.
T9, current S-4 is applied (after slope S + 0) for 30 (or T9, current S-4 is applied (after slope S + 0) for 30 (or
36) ALE cycles. 36) ALE
again
crossing is detected) crossing is
the runup time is completed (either current S + 4 or S-4 the runup time is completed (either current S + 4 or S-4
is selected, dependent upon if and when zero crossing is selected, dependent upon if and when zero crossing
occurs). occurs).
he k. k. Onc
The The
then determines the 2 most significant digits of the then determines the 2 most significant digits of the
reading. reading. For other
S+4 slopes will always be different than the number of S- S+4 slopes will always be different than the number of S-
4 4
7-F-11 7-F-11
When time T ime T2 is c 2 is comp omplet leted,
time period T3. The S + 4 current has t The S + 4 current has the
e as S-4, S-4, but but at at opposite opposite polarity.
in the other direction (i. her direction (i.e. e. the capacitor is
Aft After t er time ime T3, T3, the the S +4 S +4 cur
(slope S + 0) is applied for time T4. is applied for time T4. Time T4
time period T2 (5 or 6 ALE cycles).
When T4 is comp s complet leted, t ed, the A/
the output slope h t slope has crossed z
comparator's output (CMP
U403 pin 11) changes sta ) changes state.
After t er time TS ime TS, cur , curren rent S-4 i t S-4 is rem
(slope S-O) is applied is applied for time T6. for time T6. Since zero
When tim When time T7 e T7 is c is comp omplet leted,
for time T8. Since no zero cr Since no zero crossing was
Since Since zero zero crossing crossing was was detected
cycles. Then S + 4 is ap Then S + 4 is applied (since
detected) and so and so on. on. This takes place u
Once the e the run runup op up opera eratio tion is co
For other than a than a zero read zero reading, the number
TM 11-6625-3071-14 TM 11-6625-3071-14
ed, an S + 4 an S + 4 cur curren rent is t is
he
polarity. This This
the capacitor is
curren rent is t is rem remove oved an d and d
Time T4
cles). This is This is
he A/D Con D Contro trolle ller the r then n
as crossed zero. ero. Zero Zero
te. In the example, In the example,
s remove oved and n d and no o
Since zero
ed, no no cur curren rent ( t (slo slope pe S S
ossing was
detected during during time time
plied (since zero zero
This takes place until ntil
n is compl mplete eted, U4 d, U462 62
ing, the number of of