53A-336 Aeroflex High Voltage Scanner Card

The Aeroflex / Tektronix / CDS 53A-336 High Voltage Scanner Card is a printed circuit board assembly used in the 53/63 Series Card Cage. The Scanner Card provides 16 two-wire channels of analog signal acquisition switching at a maximum rate of 40 channels per second. Up to 10 53A-336 High Voltage Scanner Cards can be plugged into a single Card Cage to provide scanning of up to 160 channels. As many as 10 Card Cages can be chained together to provide a system with up to 1,600 high voltage channels. If the user desires, 53A-331 (10 four-wire channels per card), 53A-332 Reed Relay Scanners (20 two-wire channels per card), and 53A-336 High Voltage Scanners can be mixed in the same card cage.

A 53A-336 channel can be randomly selected (closed) by transmitting ASCII characters from the system controller (calculator or computer), to the 53/63 Series system. The card contains built-in logic to insure that any previously closed channel on any card (53A-331, 53A-332, or 53A-336) is first opened before a new channel is closed.

The 53A-336 Card is manufactured using relays specifically designed to handle the high instantaneous inrush currents that can occur when switching a mixture of high and low voltage AC or DC signals. Due to the capacitance of the cable wiring between the unit under test (UUT) and the scanner card input, instantaneous currents in excess of 10 amperes can easily occur when switching from a low voltage channel (less than 10 to 15V) to a high voltage channel (over 100V). For example, a distributed cable capacitance of 300 pF can cause an instantaneous inrush current in excess of 2A, and an instantaneous power dissipation of over 60W across a relay contact when switching from a channel at OV DC to a channel at 60V DC. Repeated inrush currents of these values may damage the typical 10-W contacts associated with reed relays. To overcome this problem, the 53A-336 Card uses relays with an inrush current capability of 35A.