HP 4001, Organizational, Ds, Gs, And Depot Maintenance Manual, Page: 14 / 73

TM 11-6625-1514-15
Section I
Paragraphs 1-6 to 1-10
1-6. Each model voltmeter has three calibrated scales
on the panel meter. The Models 400D and 400H have
two linear VOLTS scales, 0 to 1 and 0 to 3, and one
DECIBELS scale, -12 to +2 db. The meters used in
the Models 400H and 400L are larger and include a
mirror to eliminate parallax in viewing and to facilitate
use of the higher scale calibration accuracy of these
models. The Model 400L VOLTS scales are logarithmic
in calibration, from 0.3 to 1 and 0.8 to 3; and the
DECIBELS scale is linear. In all models, the VOLTS
scales are calibrated to indicate the root-mean-square
(rms) value of an applied sine wave. Actual meter
deflection is proportional to the average value of the
applied signal, thereby minimizing additional meter
deflection due to noise and harmonic distortion.
1-9. The voltmeter is equipped with a non-detachable
power cord. Test leads, which may be plain wire leads
or coaxial cable, and test probes must be supplied by
the user.
1-10. Instruments designated Models 400DR, 400HR,
and 400LR are rack mount configurations of the 400D,
400H, and 400L, respectively. They are identical to
their cabinet model counterparts in every other re-
spect. They are designed to be mounted in a stan-
dard 19 inch wide x 7 inch high relay rack space. Re-
fer to Appendix C for Replacement Parts information.
1-7. A voltmeter output signal is provided at the front
panel OUTPUT terminals. This output is proportional
to the meter reading and has a waveshape similar to the
applied signal.
This signal level is about 0.15 volts
rms for a full-scale meter reading, regardless of the
input signal level.
The internal impedance at the
OUTPUT terminal is 50 ohms over the full frequency
range.
High-impedance loads (above 100K) will not
adversely affect the accuracy of the voltmeter. This
output is valuable for increasing the sensitivity of
bridges, etc., where distortion added to the waveform
is not a factor.
1-8. The voltmeter chassis is constructed of aluminum
alloy throughout. The panel is finished in non-reflecting,
light-grey baked enamel; the cabinet is finished in
dark-blue, baked wrinkle paint. The cabinet is equipped
with rubber feet and a leather carrying handle. Control
markings on the front panel are engraved and black
filled. INPUT and OUTPUT terminals are special
binding posts which accept either bare wire or banana
plugs; the 3/4-inch spacing between binding posts accepts
standard dual-banana plugs. The “ground” side of the
INPUT and OUTPUT terminals is connected to the
instrument chassis which is in turn connected to the
power line ground through the third (round) prong of
the plug on the power cable.
1-2