Appendix D
Switching High Voltage Signals
D.1
Introduction
This section provides information on switching high voltage signal lines (up to 300 Vdc) from
Outputs 1 – 4. Outputs 1 – 4 can be configured as either 5 V
CM OS
output or a 300-Volt FET
pull down. Depending on grounding and isolation requirements, it may be necessary to isolate the
connection between the clock output and the external equipment using a small switching relay.
Several examples follow to illustrate logging applications.
D.2
Example 1: 300-Volt FET Pull Down
Figure D.1 illustrates one method of connecting the 300-Volt FET for a pull down event logging
application. Use this method with applications when it is acceptable to connect the negative side
of the FET to the 1094B chassis ground. This application could also be used with a periodic
programmable pulse (e.g. 1 Pulse Per Minute) for timing instead of event logging.
FET Specifications
•
V
DSS
= 400V, max drain-source voltage
•
R
DS
(
on
)
= 0.55Ω, max drain-source resistance
•
Id = 10 A, max continuous drain current (@ 25
◦
C)
•
P
D
= 3.1 Watts, max power dissipation
Figure D.1: 300-Volt FET with Pull-Down Resistor
