MKS HPQ3, Hardware Manual

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MKS Instruments UK Ltd
HPQ3 Hardware Manual – SP101019.101 October 2012
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Important Interfacing Notes
The 120mA maximum load for the power supply outputs is shared between the Digital and
Analogue connectors.
When interfacing digital signals between units the preferred method is to:-
a) Have a pull-up resistor/current source on all inputs to the local power supply rail. Often this
feature is provided by the digital input chip itself.
b) Use an open collector/drain/contact closure to ground as the output drive signal.
c) Where appropriate, arrange the hardware/software configuration so that an input Hi state is
a safe condition. This ensures that if a connection should be unplugged the system will go
into a fail-safe state.
d) In cases where the external equipment is some distance away and/or is likely to have a
different ground potential the fitting of opto-couplers on the interfacing should be
implemented.
Using this approach allows for easily interfacing between different voltage levels and logic families.
2.10 Ethernet
A standard RJ45 type 10/100 Base-T Ethernet connector used to connect the HPQ3 to a host PC,
hub, switch or network.
Ensure you read through the network scenarios starting on Page 22 before connecting the
unit to your network