Specifications

POWERCASSETTE FRONT-END

OPERATING MANUAL

damage due to an overload or short circuit condition. This protection is

continuous and without damage; recovery is automatic when the overload or

short circuit condition is removed. PowerCassette incorporates a “straight

line” method of current limiting. When the output current reaches an overload

threshold, the voltage begins to drop sharply so that the current, with a given

overload impedance, forces the voltage to a level which maintains the current

at an equilibrium point.

12.7 Remote Sensing. Remote sensing connections are made to pins 8 and 9

on the Positronics connector. Remote sensing is not available on the

Standby +5V, ¼ ampere output. Remote sensing is used to regulate the

output voltage at the point of load by compensating for the voltage drop in

the wires to the load. The +Sense lead (Pin 8)must be connected to the

+ side of the load and the -Sense lead (Pin 9) to the -side of the load. The

sense leads should be a color-coded, twisted pair of AWG no. 22 or 24

copper wire. See Figure 8.

Remote sensing can compensate for a total voltage drop of 0.5V, or 0.25V

per load wire. The sense leads should not exceed 10 feet (3 meters) in

length. If remote sensing is not required, the sense leads may be left

open for local sensing at the output terminals. Be careful not to reverse

the sense lead connections, as this could damage the output.

12.8 Control & Supervisory Signals. All control and supervisory signals are

accessible at the Positronics connector on the back of the unit. See Figure

5. See Section 15 for a complete description of these input and output

signals.

12.9 Alarm Signals. Among the control and supervisory signals are three logic

alarms: AC Power Fail, DC Power Good and Overtemperature Warning.

These are logic signals referenced to -Sense, Pin 9 on the Positronics

connector. AC Power Fail is a logic LO when AC input power is present. This

signal goes to a HI 4 milliseconds before the outputs go out of regulation and

stays HI for typically 15 msec. DC Power Good is a logic LO when the output

is present and in regulation and goes to a HI when there is output failure.

Overtemperature Warning is normally a logic LO but goes to a HI when the

internal air temperature reaches a critical level just prior to the unit shutting

down.