Ac Measurements Using Internal Generator - GENERAL RADIO COMPANY 1608-A Operating Instructions Manual

~ --,.-_TY_P_E_1_60_8_-A_1 M_P_E_D_A_N_C_E_B_R_I_D_G_E
_
(a.)
EXT METER
TO
BRIDGE
c
(b)
Figure 2-2. External meter connections.
EXT METER
nal detector with increased sensitivity can be used. The
external detector can be connected in series with the
internal meter, in parallel with the meter, or in place of
the meter by appropriate connection to the EXT METER
CONNECTIONS on the rear of the instrument as shown
in Figure 2-2.
2.3.5 EXTERNAL DC SUPPLY. If higher voltage is
required on the unknown resistor, an external supply
may be used. The EXT GEN terminals are connected
directly across the vertical bridge diagonal in the EXT
DC position of the function switch and the detector is
across the horizontal diagonal on the top four ranges.
Be careful not to exceed the maximum voltage or current
given in Table 2-4 in order to avoid damage to the bridge
components.
If
a higher voltage is desired on a low-valued un-
known resistor (the lower three resistance ranges), set
the function switch to EXT GEN but apply the voltage
between the BIAS terminals and the EXT DQ terminals
(R bridge only).
When an external supply or detector is used, the
measurement procedure is the same as that with the in-
ternal supply and detector except that the GEN LEV
control does not control the level of an external sup-
ply and the DET SENS control does not control the sen-
sitivity of an external detector.
2.4 AC MEASUREMENTS USING INTERNAL GENERA-
TOR.
2.4.1 1-KC CAPACITANCE MEASUREMENT.
2.4.1.1 Procedure.
a. Set the GEN LEV control fully clockwise.
b. Set the BRIDGE SELECTOR to:
C s - if the series capacitance is desired and D is less
than 1.
Cp - if the parallel capacitance is desired and D is be-
tween 0.02 and 2.
(Note: C s
=
C
p
within 0.1% if D< 0.03.)
G p - if D is greater than 2 (measure as· a conductance,
C
=
QGe.).
p
Ct;
TABLE 2-4
MAXIMUM EXTERNAL DC BRIDGE VOLTAGE AND CURRENT
BRIDGE RANGE E MAX I MAX TERMINALS
R s 1100mD 1.4v 7l0ma BIAS
R s lID
4.5v 223ma BIAS
R s 110D 14.2v 7lma
BIAS
R s
1100D 22v 17.2ma EXT GEN
R s
llkD 7lv 17.2 rna EXT GEN
R s 110kD
223v
17.2ma
EXT GEN
.R s
1100kD 400v 17.2ma EXT GEN
G
p
1000nU 400v . 17.2ma EXT GEN
12