Checking Voltage Available; Checking Loop Current - Fisher FIELDVUE DVC6200 Instruction Manual

MULTIMETER
(SEE NOTES
BELOW)
DCS SYSTEM (OR OTHER
NOTES:
1. MULTIMETER MEASURING 0.000 TO 1.0000 VDC
2. TYPICAL READINGS 0.004 VDC TO 0.020 VDC
3. OHM'S LAW—V = I x R, WHERE R = PRECISION 1 OHM RESISTOR, V = I x 1, SO V= I

Checking Voltage Available

WARNING
Personal injury or property damage
caused by fire or explosion may occur
if this test is attempted in an area
which contains a potentially explosive
atmosphere or has been classified as
hazardous.
To check the Voltage Available at the instrument,
perform the following:
1. Connect the equipment in figure 2-11 to the field
wiring in place of the FIELDVUE instrument.
2. Set the control system to provide maximum output
current.
3. Set the resistance of the 1 kilohm potentiometer
shown in figure 2-11 to zero.
4. Record the current shown on the milliammeter.
5. Adjust the resistance of the 1 kilohm potentiometer
until the voltage read on the voltmeter is 11.0 volts.
6. Record the current shown on the milliammeter.
7. If the current recorded in step 6 is the same as that
recorded in step 4 (± 0.08 mA), the voltage available is
adequate.
September 2010
Maintenance and Troubleshooting
0.020
LOOP + / TEST +
TEST −
LOOP + / TEST +
LOOP −
−
+
4−20mA
CURRENT
SOURCE
CURRENT SOURCE)
Figure 7-6. Check the Loop Current using the TEST Terminals
DVC6200 DIGITAL VALVE
CONTROLLER TERMINAL BOX
8. If the voltage available is inadequate, refer to
Wiring Practices in the Installation section.
Checking the Loop Current Without
Disturbing the Loop Wiring
WARNING
Personal injury or property damage
caused by fire or explosion may occur
if this test is attempted in an area
which contains a potentially explosive
atmosphere or has been classified as
hazardous.
To check the loop current without disturbing the loop
wiring perform the following procedure.
1. With the FIELDVUE instrument connected to a
current source connect a digital multimeter reading
Volts DC ( 0 to 1 VDC or mV scale) to the TEST
terminals as shown in figure 7-6.
2. The reading at the test terminals is proportional to
the loop current [0.004 V = 0.004 A (4 MA)] mA of
loop current). Refer to Specifications, table 1-2, to
determine if the current is sufficient.
TEST −
LOOP + / TEST +
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