Input And Output - HP 400D Operating And Service Manual

Section I
Paragraphs 1-6 to 1-12
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.
1-7, 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
T.O, 33A1-12-349-1
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 ina stan-
dard 19inchwide x 7inch high relay rack space. Re-
fer to Appendix C for Replacement Parts information.
1-11. ACCESSORIES.
1-12. Accessory instruments for the voltmeter are
available (not supplied) to increase its range of opera-
tion and application, such as increasing voltage mea-
surement range and input impedance, converting to
current measurement, providing line matching, ete.,
as follows:
a. H-P 11004A Line Matching Transformer. Pro-
vides balanced 135-ohm or 600-ohm input, 5 ke to 600
ke.
b. H-P11005A Bridging Transformer. Allows volt-
age measurement on balanced lines. 20 cps to 45 kc.
c, H-P 11039A Capacitive Voltage Divider. Safely
measures power-frequency voltages to 25 kilovolts.
Division ratio, 1000:1. Input capacity, 15 pf +1 pf.
d. H-P 11041A Capacitive Voltage Divider. Accu-
racy +3%. Division ratio, 100:1. Input impedance,
50 megohms, resistive, shunted with 2.75 pf capa-
city. Maximum voltage, 1500 volts.
e. H-P 456A AC Current Probe. Allows current
measurements without breaking the circuit, Sensitivity
1 mv/ma +2% at 1 kc. Maximum input 1 amp rms;
2 amp peak, Output noise less than 50 uv rms,
f. H-P 11029A-11034A Shunt Resistors, For mca-
suring currents as small as 1 microamp full scale,
Accuracy +1% to 100 ke, +5% to 4 me (470A, 45% to
1 mc), Maximum power dissipation, 1 watt.
00102-3