HP Q METER 4342A User Manual

Section III
Model 4342A
Paragraphs 3-69 and 3-70
Parallel Connection Measurements
pointer scales out at the left end of
the scale (AQ full scale), reset the
function to normal Q measurement. The
difference in Q is calculated from the
two Q values as AQ = Q1 - 42.
g.
Capacitance value of the unknown capa-
citor is:
cp = Cl - c2
. . . . ..*...m*.. (eq. 3-23)
Q value of the unknown is:
Q = QlQz(C1 - c2)
*QCl
. . . . . . . . (eq. 3-24)
where, AQ = Q1 - 42
and equivalent parallel resistance of
the unknown is:
Rp = -$$$- (n) . . . . . . . . . . (eq. 3-25)
where,
w= 2Tfl.
3-69.
High Resistance Measurement.
3-70.
When the measuring circuit is resonat-
ed using a reference inductor, a resistor
placed in parallel with the tuning capacitor
will lower the indicated Q in inverse propor-
tion to the sample value.
This reduction of
Q is utilized to measure the resistance. TO
avoid a significant increment of measurement
error, the measurement should be made for
resistors within a reasonable range.
For
high resistances, the change in the indicated
Q should be greater than the Q meter resolu-
tion, that is, 0.1 on AQ = 3 range, 0.3 on
10 range, 1 on 30 range and 3 on 100 range,
respectively. For relatively low resist-
ances, the indicated Q should be higher than
10 when the sample is connected.
See Figure
3-5 for suitable sample value ranges.
To measure high resistances, proceed as
follows:
a. Depress appropriate FREQUENCY RANGE
button and set FREQUENCY dial control
to the desired frequency.
b. Connect a suitable reference inductor
to measurement COIL (HI and LO)
terminals.
C.
Adjust L/C dial and AC dial controls
for maximum panel Q meter deflection.
Note sum of the C dial and AC dial
readings as Cl and panel meter reading
91.
Note
The reference inductor should be
selected so that high resistances
are measured with a low tuning
capacitance and relatively low re-
sistances are measured with a high
tuning capacitance.
d.
Depress AQ button and adjust AQ ZERO
(COARSE and FINE) controls so that
meter pointer indicates zero (full
scale) on AQ scale.
Note
Press AQ button to release AQ func-
tion and recheck for correct reso-
nance. Again depress the AQ button
and recheck for AQ zero indication.
e.
Connect the unknown resistor to meas-
urement CAPACITOR (HI and GND)
terminals.
f.
Restore resonance by adjusting the L/C
and AC dial controls.
Note sum of the
C dial and AC dial readings as C2 and
panel meter AQ reading. If meter
pointer scales out at the left end of
the scale (AQ full scale), reset the
function to normal Q measurement.
The difference in Q is calculated from
the two Q values as AQ = Q1 - 42.
g.
The resistance of the unknown resistor
is:
Rp = ---$$& (CL) . . . . . . . . . . (eq. 3-26)
Where, w = 2~ times the measurement
frequency.
If the sample is also reactive, its
reactance is:
xp =
1
w(G2 - Cl)
(CL) . . . . (eq. 3-27)
(usually capacitive)
and its capacitance is:
cp = Cl - c2 . . . . . . . . . . . . . . (eq. 3-28)
If the sample appears inductive, Cz is
larger than Cl.
3-20

HP Q METER 4342A Specifications

General

Brand	HP
Model	Q METER 4342A
Category	Measuring Instruments
Language	English