SVI-II Instruc Man.book - Fagerberg

Masoneilan Dresser
SVI II AP Instruction Manual
Supplemental Power Supply
Another approach is to boost the compliance voltage of the DCS using a
supplemental power supply (see Figure 37 on page 81) with the split ranged
SVI II AP positioners 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 volts for each additional SVI II AP. Exceeding the values in Table 17
below will cause damage if the signal wires are short-circuited.
Table 17 Supplemental Voltage for Split Range
Number of SVI II APs on a Current
Loop
Maximum Allowable Supplemental Voltage
1 0
2 9.0 VDC
3 18.0 VDC
Verify Wiring and Connections
For split range installations there are additional constraints on the split range
system: the minimum span must be 5 mA; the upper range value must be 8
mA to 20 mA; the lower range values must be 4 mA to 14 mA.
Use the following procedure to ensure that the SVI II AP 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.
Current is read from the local display or with a milliammeter
installed in series the SVI II AP.
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 milliammeter in series with the current signal. Verify
that source can supply 20 mA to SVI II AP input.
If 20 mA is not attainable, see troubleshooting.
Note:
Improperly or inadequately grounded installations can cause noise or
instability in the control loop. The internal electronic components are
isolated from ground. Grounding the case is unnecessary for
functional purposes but grounding the case may be necessary to
conform to local codes.
80