Operating Considerations.
Operating Considerations.
WA R N I N G
Do not connect either the 34937A, 34938A or 34939A module directly to a mains power outlet. If it is necessary to switch a mains voltage or any circuit where a large inductive load may be switched, you must add signal conditioning elements to reduce the potential transients before they reach the module or the Analog Buses.
Electrical Considerations
See the Introduction to the Plug In Modules chapter of the 34980A Mainframe User’s Guide for detailed environmental operating conditions for the 34980A mainframe and its installed modules. That guidance sets maximum per channel current and power ratings at rated voltage for pollution degree 1 (dry) and pollution degree 2 (possible condensation) conditions, for each of the GP modules.
Temperature Sensor
A temperature sensor on these modules triggers system interrupts when high- carry current- induced heat on the modules is excessive and sets the HOT annunciator on the front panel. This over- temperature situation generates an SRQ event when the factory- set 70 oC threshold is reached. It is up to the user to determine what, if any, action should be taken.
Switching Reactive Loads
Reactive loads (those that include significant inductance or capacitance) can cause voltage spikes or current spikes during switching operations. The general purpose modules are designed for switching reactive loads. The optional 34937T and 34938T terminal blocks have solder pads for adding snubber circuits for the 5 A relays to reduce the reactive transients. See the drawings on page 8 and page 11 for the locations of snubber circuit pads and installation information about a snubber circuit.
Hardware Power-Fail Jumper
A hardware jumper on the 34937A and 34938A modules allows you to define the power- failure states for the modules’ 5 A latching relays. Depending on the position of the jumper, the 5 A relays will either open or maintain state when system power failure occurs.
On the 34939A module, a hardware jumper allows you to define the power- failure state affecting all 64 of the module’s 1 A latching relays. Depending on the position of the jumper, these relays will either open or maintain state when system power failure occurs.
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