Omega Engineering PX2670 - Manual (Page 5)

Loop Power Supply
vs.
Loop Resistance for 4 to 20mA Transmitters
800
0
Loop Resistance (Ohms)
30
Loop Supply Voltage (Vdc)
Operating
Range
Figure 4
Zero Adjustment - Voltage
While monitoring the voltage between the positive output (+OUT) and common (-OUT),
and with both ports open to atmosphere, the zero may be adjusted. For unidirectional
pressure ranges, turn the zero adjustment screw until a reading of 0.050 VDC is
achieved. For bidirectional pressure ranges set to 5 VDC.
Zero Adjustment - Current
While monitoring the current output with both ports open to atmosphere, the zero may be
adjusted. For unidirectional pressure ranges, turn the zero adjustment screw until a
reading of 4 mA is achieved. For bidirectional pressure ranges, set the zero to 12 mA.
Span Adjustment - Voltage
Span or full scale output adjustments should only be performed by using an accurate
pressure standard (electronic manometer, digital pressure gage, etc.)
with at least
comparable accuracy as the PX2670 Series. With full scale pressure applied to the high
pressure port, adjust span for full scale electrical output of 10.05 VDC.
Example 1: Unidirectional pressure range of 0 to 1” WC and 0.05
to 10.05 VDC output. Apply 1” WC to the high
pressure port and adjust span as close as practical to
10.05 VDC.
Span Adjustment - Current
Span or full scale output adjustments should only be performed by using an accurate
pressure standard (electronic manometer, digital pressure gage, etc.) with at least
comparable accuracy as the PX2670 Series. With full scale pressure applied to the high
pressure port, adjust span for full sale electrical output of 20mA.
Example 1: Unidirectional pressure range of 0 to 1” WC
Apply 1” WC to the high pressure port and adjust span as close
as practical to 20 mA.
Example 2: Bidirectional pressure range of
±
5” WC
Apply 5” WC to the high pressure port and adjust span
as close as practical to 20 mA.
Apply -5” WC to the high pressure port and adjust span
as close as practical to 4 mA.
9