Masoneilan SVI3 Installation and Maintenance Manual
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7.7.3 Supplemental Power Supply
Another approach is to boost the compliance voltage of the DCS using a supplemental
power supply (see Figure 40 on page 118) with the split ranged SVI3 connected in series
with the supply
.
It is not practical to use supplemental supplies when Intrinsic Safety is
required. The barriers do not permit adequate voltage. Contact the DCS vendor to verify
that the output circuit is compatible with the added voltage. The supplemental voltage
must equal 9
.
0 V for each additional SVI3. Exceeding the values in Table 23 will cause
damage if the signal wires are short-circuited.
7.7.4 Verify Wiring and Connections
Use the following procedure to ensure that the SVI3 split range system is properly
powered:
• Connect a DC voltmeter across the input terminals.
• For an input current value between 4 and 20 mA the voltage varies between 11 V
and 9 V respective. See “Split Range Applications” on page 114.
• Current is read from the local display or with a milliampmeter installed in series the
SVI3.
• When voltage exceeds 11 V check that polarity is correct.
• If voltage is less than 9 V and polarity is correct, voltage compliance of current
source is inadequate.
• Connect a milliampmeter in series with the current signal. Verify that source can
supply 20 mA to SVI3 input.
• If 20 mA is not attainable, troubleshoot the source and set up.
Table 23: Supplemental Voltage for Split Range
Number of SVI3s on a Current Loop
Maximum Allowable Supplemental Voltage
1
0
2
9.0 VDC
3
18.0 VDC
