Part 2

Plug-In Assembly Configuration 51 9(a) WRITE ONLY DATA BUS CONNECTIONS(b) DATA BUS CONFIGURATION FOR READ OPERATIONDATALATCH--READBUFFERORLATCH/-'-+DATALATCHFigure 159.Option 140 - Rear and Write Data Bus ConnectionsControlling Noise on the Signal LinesBecause of the distributed nature of the 3497A backplane signals, noise may be presenton the control and data bus lines. The noise can be controlled somewhat byfiltering. The preferred method is to buffer the lines with Schmitt Triggers, using ICssuch as an SN74LS14.Regardless of the method used to control noise, it will introduce some signal delay.Be sure to account for these delays so that timing requirements are not violated.Typically, an oscilloscope is used to check signal lines for proper levels, noise, etc.When doing these measurements, make the measurement at the signal source andkeep the ground lead of the scope as short as possible. An effective way to minimizeground lead length is to use a probe tip ground spring.Power SwitchingTwo terminal blocks are provided on the board which permit up to 20 external connections.These terminal blocks are rated at 100 VA or 170V peak betwen any twoterminals or any input to chassis and must be fused accordingly.Inductive loads may require contact protection (arc suppression). If your applicationrequires switching inductive loads, see the discussion on contact protection in theOption 11 5 (High Voltage Actuator) part of this chapter.To minimize interference caused by high voltage switching, maintain maximum isolationbetween the switched voltages and the 3497A logic circuitry and choose relayswhich have a low contact-to-coil capacitance.Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com