Omega Engineering PX2670 - Manual (Page 4)

Current Models
The current output transmitters are true 2-wire (See Figure 2), 4-20 mA current devices
and deliver rated current into any external load of 0-800 ohms. The 4-20 mA current
units are designed to have current flow in one direction only - please observe polarity.
The PX2670 can operate over a voltage range of 9 to 30 VDC. It has been factory
calibrated at 24 VDC into a 250 ohm load. The minimum and maximum power supply
must be capable of delivering these voltages to the PX2670. Thus, the
minimum and maximum power supply calculation is shown and depicted in Figure 4.
MIN Supply Voltage: 9 + 0.02 x (resistance of receiver plus line)
MAX Supply Voltage: 30 + .004 x (resistance of receiver plus line)
Mounting and Pressure Fittings
Mounting
The PX2670 Series are designed to be mounted with the two holes located on the base
of the housing. The holes are sized to accept a #8 screw.
Fittings
Two (2) 3/16” O.D. pressure fittings are supplied for pressure signal connection with a
1/4” push on tubing. Both positive (high) and negative (low) pressure ports are located
on the bottom face side of the unit. For best results (shortest response time), 3/16” I.D.
tubing is suggested for tube lengths up to 100 feet long, 1/4” I.D. for tube lengths up to
300 feet long, and 3/8” I.D. for tubing lengths up to 900 feet. The high and low ports are
labeled next to each respective port (see Figure 3).
Calibration
All PX2670 Series pressure transducers
and transmitters are factory calibrated and
should require no field adjustment. How-
ever, both zero and span adjustments are
accessible under the cover of the unit (see Figure 1), below and to the right of the
terminal strip. Whenever possible, any zero and span adjustments should be corrected
by software in the user’s control system. Us the zero and span adjustments only if
necessary. The PX2670 Series are calibrated in the vertical position at the factory
(baseplate vertical). For use in other orientations, position the unit and follow the zero
adjustment procedure listed below. Pressure ranges are fixed and cannot be changed
in the field. If a range change is required, contact the factory for a replacement PX2670
model with the appropriate pressure range.
Figure 3
Figure 2A Figure 2
Power
Supply
PX 2670
Transmitter
(4 to 20 mA)
Load
(Monitor)
+ +
_ _
_
+
Power
Supply
PX 2670
Transducer
(Voltage)
Load
(Monitor)
+ +
_ _
_
+
The Model 267 voltage output is a 3-wire circuit, with three terminals available for wiring
(see Figure 1). The -Excitation and -Output are commoned on the circuit (see Figure 2A).
The 267 voltage output can operate from either AC (9-30 VAC) or DC (12-40 VDC)
excitation. The 267 has a 0-10 VDC output, calibrated at the Factory.