Operating Instructions—Type 422 AC-DC
The battery pack can be charged even when the AC-DC
Power supply is removed from the indicator if the Power
Mode switch is in the correct position and the POWER
switch is turned on at the power supply. This feature
provides a means of continuous operation from batteries if
more than one supply is available. It also provides a method
of trickle charging the battery pack without the instrument
in operation if the batteries must be stored for long periods
of time (Power Mode switch set to OPERATE 230V AC or
OPERATE 115V AC).
The battery pack can be charged over an ambient temp
erature range of —15° C to +40° C. However, the maxi
mum operating time and useful battery life is provided
when the batteries are charged and discharged at about
+25° C (see Table 2-2). Thermal cutouts in the AC-DC
Power Supply protect the battery pack from overheating
during charge time. The battery pack normally becomes
warmer as it reaches full charge potential. If the tempera
ture surrounding the battery pack exceeds the safe opera
ting level, a thermal cutout switches the charge rate from
the 400 milliampere full-charge to the 30 milliampere
trickle-charge rate. When the temperature returns to a safe
operating level, the thermal cutout returns the charge rate
to the 400 milliampere level. If the charge rate is reduced
for an extended period during a charge cycle, the battery
pack will not reach full charge in the recommended 16-hour
charge time. Therefore, do not assume battery pack failure
because of reduced operating time. Instead, recharge the
battery pack for 16 hours at a reduced ambient tempera
ture and then check the operating time. If insufficient oper
ating time is still obtained, the battery pack is probably
defective (see Battery Pack Maintenance in Section 4 for
more information).
During normal usage or storage, the individual battery
cells in the battery pack acquire slightly different charge
characteristics. To provide the best overall operation and
maximum operating life, the charge on the individual bat
tery cells should be equalized periodically. This can be done
without damage to the battery cells by charging the batter
ies at the full charge rate for 24 hours (be sure ambient
temperature is low enough to prevent opening of the ther
mal cutout). This should be done after every 15 charge-
discharge cycles or every 30 days, whichever occurs first.
Battery-Pack Maintenance and Troubleshooting. Com
plete information on maintenance and troubleshooting of
the battery pack is given in Section 4.
Battery Pack Storage. The battery pack used in the AC-
DC Power Supply can be stored in a charged or a partially
charged condition. For best shelf life when storing the bat
tery pack for long periods of time, fully recharge the bat
tery pack about every three months. Although the battery
pack is fully charged when shipped from Tektronix, Inc.,
recharge the battery pack completely before operating the
instrument.
Charge retention characteristics of nickel-cadmium bat
teries vary with the storage temperature and humidity. The
battery pack may be stored at ambient temperatures be
tween —40°C and +60°C without damage, either in the
instrument or as a separate unit. However, the self-discharge
rate increases with ambinet temperature. For example, cells
stored at +20°C will lose about 50% of their stored charge
in three months but when stored at +50°C, they will be
almost completely self-discharged in only one month. High
humidity also increases the rate of self-discharge. If this
instrument must be stored at either high ambient tempera
ture or high humidity for an extended period of time, it is
recommended that the battery pack be continuously trickle
charged (charge battery pack completely at full-charge rate
before extended trickle charge).
The POWER light blinks to indicate when the battery
pack voltage is too low for continued measurement accura
cy. The batteries used in this instrument may be damaged
by excessive discharge. Therefore, the instrument should
not be operated from the battery pack after the POWER
light begins to blink, since such operation not only may
provide inaccurate measurements, but may also shorten the
useful life of the battery pack.
Operating the Power Supply Remotely.
The indicator can be operated with the power supply
removed for maintenance, calibration or special applica
tions. The interconnecting plug on the rear of the indicator
can be detached and used as an extension cable. To remove
the interconnecting plug, loosen the three secrews holding
it to the indicator and slide it up slightly; then move it
away from the rear of the indicator. Unwrap the power
cable from the rear of the indicator.
The two spring clips on the power supply circuit board
are provided to secure the power cable to the power supply
for remote operation. To use the clips, first be sure the
POWER switch is set to OFF at the power supply. Then,
hook one spring clip into the hole provided in the intercon
necting plug (see Fig. 2-5). Slide the plug into place while
depressing the other spring clip. To remove the plug, reverse
the order in which it was attached.
CAUTION
Do not bend the spring clips so they latch without
using the procedure described here. Otherwise, they
will latch when the power supply is remounted on the
indicator and will be difficult to remove without
damage to the instrument.
When operating the power supply remotely, the POWER
switch on the front of the indicator is inoperative. The
POWER switch can be actuated at the power supply. The
ON and OFF positions of the switch are noted on the cir
cuit board.
Low-Batteries Indicator
2-6
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