Fluke 863, Service Manual

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867B,863
Service Manual
2-8
Power ON/OFF Requirements 2-8.
The GMM is turned off when the selector is rotated to OFF. If the selector is
immediately rotated beyond OFF, the GMM does not turn off. If the selector remains in
OFF for 125 ms, GMM software recognizes a valid OFF signal. If the selector remains in
the OFF position for more than 250 ms and an OFF signal is not generated, a hardware
timeout occurs and the GMM powers off.
The signal PWR_RESET* goes true (LOW) immediately when a software OFF signal or
hardware timeout is generated. This action forces a complete restart sequence, with
PWR_RESET* remaining low for at least 100 ms.
After a software OFF signal has occurred, turn the GMM on by rotating the selector to
any function or by pressing (the WAKEUP button.). If a hardware timeout has
occurred, pressing does not turn the GMM on; the selector must be rotated to a new
function.
NiCd Charging Requirements 2-9.
Models 867B use an internal two-state charger. The initial charge state is at
approximately 170 mA (
±
30 mA) to allow for full overnight charging (16 hours
minimum). The second charge state is at approximately 40 mA (
±
15 mA) to allow for
battery charge maintenance without full charging from a discharged condition.
A timer (reset each time the battery eliminator is plugged in) controls the charge state.
The rate shifts to 40 mA after approximately 16 hours of accumulated charge time.
The 40-mA rate is used with batteries below approximately 6 volts to limit the amount of
power dissipated when a completely dead battery pack is used. After this 6-volt cutoff
point has been reached, the GMM starts charging at 170 mA.
Battery and Line Level Detection 2-10.
The BATT_LVL signal is an attenuated version of the battery and charging voltages.
Table 2-4 summarizes the values to be used by the software to control LOW BATTERY
detection and SOFT SHUTDOWN. After LOW BATTERY is detected, the backlight is
turned off and backlight control is disabled.