Campbell Scientific SDM-CVO4 4-Channel Current/Voltage Output Module - Manual (Page 15)

SDM-CVO4 4-Channel Current/Voltage Output Module
Where the SDM-CVO4 is going to be used in applications where the potential
difference between the datalogger and the output terminals exceeds 50 V RMS
AC, 74 VDC then careful consideration has to be taken to ensure safe
operation and compliance with local safety regulations. For such applications
Campbell Scientific does not supply the device as a stand-alone device which
will meet all safety requirements. The SDM-CVO4 is supplied as a component
for the user to install in a system that is, itself, designed to comply with such
regulations. The following guidance is given to help users meet the
requirements of such regulations.
The SDM-CVO4 is designed such that the internal safety barrier meets the
requirements of BS EN 61010-1 (similar to IEC 950). However, the method of
wire connection and earthing facilities prevents the unit being claimed as
compliant with such standards, when supplied as a stand-alone unit.
To meet the safety requirements of most countries, wires carrying hazardous
voltages, terminated in screw terminals must be housed in an enclosure
requiring a tool to open it, and the enclosure must have international symbols
on the outside warning of high voltages. An additional warning label, in the
local language, may be required stating that the source of hazardous voltage
must be turned off before the enclosure is opened.
The exact nature of the enclosure is covered by the standards, but an enclosure
designed to house electrical equipment will usually meet the requirements.
Campbell Scientific's ENC 12/14 or 16/18 enclosures meet these requirements
if fitted with a padlock and with the correct labels on the door.
It is also necessary to ensure that metal parts on the outside of the enclosure
that might come in contact with active high voltage circuits are connected to a
safety ground. The ground lug of Campbell Scientific enclosures is the main
issue for the above enclosures, but this would, in any case, normally be the
point of contact to a good ground point.
Cables that connect to the output of the SDM-CVO4 should have adequate
strain relief at the point of exit from the enclosure, and the cable and any
connectors used should be rated to a high enough voltage and assembled in a
safe fashion.
If possible, the external device which is operating at a high voltage relative to
ground should be configured with an earth leakage breaker system to
disconnect it from the voltage source in the event of a breakdown of the
insulation in the system causing a leak to ground.
With a system made to the above requirements the maximum recommended
continuous operating voltage between the datalogger and input is 240 VAC.
This value is derived from the voltage rating of the terminal blocks used and an
internal suppression capacitor (see below).
The unit is designed to withstand a transient flash test of 1500 V RMS AC, for
two seconds. However, you need to be aware of some aspects of the design
which can influence the results of such a test if made.
a) To help suppress emissions of electromagnetic interference the
isolation barrier is bridged by a 1nF, class ‘Y’ safety capacitor. This
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