HP (Hewlett-Packard) 6205B ユーザーズマニュアル

following formula:

g.

The output impedance (Z

out

) should be

less than 0,020 ohms.

h. Using formula of Step f, calculate output

impedance at frequencies of 50kHz and 500kHz.

Values should be less than 0.5 ohm and 3.0 ohms,

respectively.

Figure 5-10.

Output Impedence, Test Setup

5-40 Temperature Coefficient.

Definition: The change in output

voltage per degree Centigrade
change in the ambient temperature
under conditions of constant input
ac line voltage, output voltage

setting, and load resistance.

5-41 The temperature coefficient of 

a power sup-

ply is measured by placing the power supply in an
oven and varying it over any temperature span
within its rating.

(Most   power supplies are

rated for operation from 0°C to 55°C. ) The power

supply must be allowed to thermally stabilize for

a sufficient period of time at each temperature of
measurement.

5-42 The temperature coefficient specified is the
maximum temperature-dependent output voltage
change which will result over any 5°C interval.
The differential voltmeter or digital voltmeter
used to measure the output voltage change of the

supply should be placed outside the oven and
should have a long term stability adequate to in-
sure that its drift will not affect the overall meas-

urement accuracy.

5-43 To check the temperature coefficient, pro-

ceed as follows:

a .

b. Turn CURRENT controls fully clockwise

and adjust front panel VOLTAGE controls until the

front panel voltmeter indicates 10Vdc.

c.

Insert the power supply into the temper-

ature-controlled oven (differential voltmeter and

load resistance remain outside oven). Set the

temperature to 30°C and aIlow 30 minutes warm-
up.

d. Record the differential voltmeter indica-

tion.

e .

Raise the temperature to 40°C and allow

30 minutes warm-up.

f.

The differential voltmeter indication

should change by less than 90mV from indication

recorded in Step d.

5-44

5-45

Output Stability.
Definition: The change in output
voltage for the first eight hours
following a 30 minute warm-up
period. During the interval of
measurement all parameters,

such as load resistance, ambi-

ent temperature, and input line
voltage are held constant.

This measurement is made by monitoring the

output of the power supply on a differential volt-
meter or digital voltmeter over the stated measure-
ment interval; a strip chart recorder can be used

to provide a permanent record. A thermometer
should be placed near the supply to verify that the

ambient temperature remains constant during the
period of measurement. The supply should be put

in a location immune from stray air currents (open
doors or windows, air conditioning vents); if pos-

sible, the supply should be placed in an oven

which is held at a constant temperature. Care
must be taken that the measuring instrument has a

stability over the eight hour interval which is at
least an order of magnitude better than the stabil-
ity specification of the power supply being meas-

ured. Typically, a supply may drift less over the
eight hour measurement interval than during the ½
hour warm-up period.

5-46 Stability measurement can be made while

the supply is remotely programmed with a fixed
wire-wound resistor, thus avoiding accidental
changes in the front panel setting due to mechan-

ical vibration or “knob-twiddling. “

5-8