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Dwyer MSXP-W20-PA Series MSX Pro Magnesense Differential Pressure Transmitter, +/-0.5 in WC (125 Pa / 12.5 mm WC) Bidirectional, Wall Mount, Dual 4-20mA + 0-5/10V Output, +/-0.5% FSO, NEMA 4X

Dwyer MSXP-W20-PA Series MSX Pro Magnesense Differential Pressure Transmitter, +/-0.5 in WC (125 Pa / 12.5 mm WC) Bidirectional, Wall Mount, Dual 4-20mA + 0-5/10V Output, +/-0.5% FSO, NEMA 4X

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MSRP: $211.80
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SKU:
MSXP-W20-PA
Condition:
New
Availability:
58 In Stock
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Range (Full Scale)+/-0.5 in WC (125 Pa / 12.5 mm WC)
DirectionBidirectional
Mount TypeWall Mount
Output Signals4-20mA + 0-5/10V (Dual)
DisplayNo Display
Accuracy+/-0.5% FSO
EnclosureNEMA 4X / IP66
Plenum RatedUL 2043

The Dwyer Series MSX Pro MSXP-W20-PA is a Magnesense differential pressure transmitter built for critical building performance applications - filter monitoring, duct static pressure, clean room and isolation room differential, air velocity and flow measurement in VAV systems, and other commercial HVAC and BAS work where stability and long-term accuracy matter. This is the +/-0.5 in WC (125 Pa / 12.5 mm WC) bidirectional wall-mount configuration with factory-default Pascals display units. +/-0.5% FSO typical accuracy, +/-1% FSO/year long-term stability. The MSX Pro carries a NEMA 4X / IP66 rating with plenum-rated (UL 2043) and UL94 V-0 flame-rated housing. This SKU is the no-display variant. The MSX Pro can be ordered with an optional LCD; the A-MSXP-LCD replacement display is available separately if you want to add one later.

Best for: low-pressure room and zone work - building static pressure, clean room and isolation room dP, laboratory exhaust hood proving, and pharmaceutical and semiconductor cleanroom verification where 0.5 in WC full scale is the right resolution. The wall-mount configuration matches a flat-panel or wall installation where tubing runs from the transmitter back to a static pickup or pitot tube in the duct.
DWYER
WARRANTY
Manufacturer warranty backed by Dwyer. Coverage per Dwyer's standard Terms and Conditions of Sale (refer to the Dwyer catalog or workorder for current terms). ZOT Supply is an authorized Dwyer / DwyerOmega distributor; product ships factory-new with full manufacturer warranty intact and access to Dwyer technical support.

Key Features

Magnesense Pressure Sensing

Built on Dwyer's Magnesense sensing platform - the same technology used in the original MS2 Magnesense II. Delivers exceptional long-term stability (+/-1% FSO per year) for critical building performance applications where drift over time matters more than initial accuracy.

Dual Simultaneous Output

Provides BOTH a 4-20 mA current output AND a 0-5/0-10 VDC voltage output from the same unit at the same time. One signal can drive the BAS analog input while the second goes to a panel meter or chart recorder for verification. Rare feature in this class - useful when commissioning needs redundant signal paths.

Field-Selectable Range, Direction, Response

Internal DIP switches set the pressure range (4 sub-options per range tier), unidirectional or bidirectional mode, response time (instantaneous default or 3-second damping), voltage output (0-5 V or 0-10 V), and display units (Pa, mm WC, or in WC). Factory-set per the order code; field-adjustable without returning the unit.

Velocity & Flow with Built-In Square Root

Beyond pressure, the MSX Pro can switch to velocity or flow output mode with the square-root extraction handled in the transmitter itself. Useful for VAV applications, pitot-tube airflow measurement, and CFM totalization without needing a separate signal conditioner. K-factor and duct-area parameters are entered via the front-panel menu (LCD models) or DIP switches.

Flip-Lid + Tamper-Resistant + Toolless Terminal

Hinged flip-lid housing simplifies wiring access; tamper-resistant cover deters field tampering. Liquid-tight cable gland fitting protects the cable egress from moisture, and the toolless removable European-style 4-wire terminal block (16-26 AWG) speeds up installation - no screwdriver needed for the field-side terminals.

NEMA 4X / IP66 + Plenum Rated

Watertight NEMA 4X (IP66) enclosure rating for harsh and washdown environments. UL 2043 plenum-rated for installation in air handling spaces, and UL94 V-0 flame-rated for code-compliant placement. The right pick when the install environment is wet, dusty, or above-ceiling.

Selectable Sub-Ranges

This SKU's Range 0 sensing element supports 4 selectable sub-ranges set by DIP switches 7 and 8 (see the installation manual for the switch positions). The factory full-scale output is the largest value in the table - sub-ranges 1-3 are available without returning the unit.

DIP PositionInches WCPa (Set 1)Pa (Set 2)mm WC
10.05 in WC15 Pa60 Pa1.25 mm WC
20.1 in WC25 Pa75 Pa2.5 mm WC
30.25 in WC40 Pa100 Pa5 mm WC
40.5 in WC50 Pa125 Pa12 mm WC

Position 4 (0.5 in WC / 125 Pa / 12 mm WC) is the factory full-scale value (factory full scale) for Range 0.

Technical Specifications

SpecificationValue
ModelMSXP-W20-PA
SeriesSeries MSX Pro Magnesense
Pressure Range (Full Scale)+/-0.5 in WC (125 Pa / 12.5 mm WC)
DirectionBidirectional
Mount TypeWall Mount
Selectable Sub-Ranges (in WC)0.05 in WC, 0.1 in WC, 0.25 in WC, 0.5 in WC
Selectable Sub-Ranges (Pa - Low Set)15 Pa, 25 Pa, 40 Pa, 50 Pa
Selectable Sub-Ranges (Pa - High Set)60 Pa, 75 Pa, 100 Pa, 125 Pa
Selectable Sub-Ranges (mm WC)1.25 mm WC, 2.5 mm WC, 5 mm WC, 12 mm WC
Display Unit (Factory Default)Pascals
Display Units (DIP-Selectable)Pa (low or high set), mm WC, or in WC
Accuracy+/-0.5% FSO for all ranges except unidirectional 0.5 in WC range
Stability+/-1% FSO per year
Service / MediaAir and non-combustible, compatible gases
Output Signals4-20 mA (2-wire) AND 0-10 V or 0-5 V (3-wire), simultaneous
Voltage Output SelectionDIP switch 4: 0-10 V (default) or 0-5 V
Power Requirements10-36 VDC (2-wire current); 17-36 VDC or 21.6-33 VAC isolated (3-wire voltage)
Current Consumption21 mA max continuous
Loop ResistanceCurrent output: 0-1250 ohms max; Voltage output: 1 kohm minimum load
Response TimeInstantaneous (default) or 3 seconds (DIP-selectable)
Zero and Span AdjustmentsDigital push-button
Pressure Limits3.6 psi max operation, 6 psi burst
Temperature Limits-4 to 158 F (-20 to 70 C)
Process Connections1/8 in, 3/16 in, 1/4 in, 5 mm, and 6 mm ID flexible tubing
Electrical Connections4-wire removable European-style terminal block, 16-26 AWG
Electrical Entry1/2 in NPS thread, liquid-tight cable gland included
Enclosure RatingNEMA 4X (IP66); UL 2043 (plenum); UL94 V-0
Mounting OrientationPressure sensor measurement unaffected by orientation
DisplayNone (A-MSXP-LCD replacement display available)
Weight8.0 oz (230 g)
ComplianceCE
ManufacturerDwyer Instruments, LLC (DwyerOmega)
Manufacturer Part NumberMSXP-W20-PA

Documentation

PDFProduct Datasheet (DS-MSXPRO Rev 6)PDFInstallation & Operating Instructions (P-MSXP-A)PDFQuick Start Guide

Frequently Asked Questions

What pressure range does the MSXP-W20-PA measure?
This is the Range 0 sensing element, factory-set to +/-0.5 in WC (125 Pa / 12.5 mm WC) bidirectional. The same physical unit supports 4 selectable sub-ranges via DIP switches 7 and 8 inside the housing: in inches WC the options are 0.05, 0.1, 0.25, 0.5 in WC. The factory full-scale value is the largest of these. You can field-set a smaller sub-range (and re-zero the unit) without returning the transmitter.
What is dual simultaneous output and when should I use it?
The MSX Pro provides both 4-20 mA and 0-5/0-10 VDC outputs from the same unit at the same time - they're not selectable, they're simultaneous. Use the current output to feed your BAS analog input (more noise-immune over long cable runs) AND the voltage output for a local panel meter, chart recorder, or secondary controller. Useful during commissioning when you want a parallel signal path for verification, or in retrofit applications where the existing control panel uses voltage and the new BAS uses current. NOTE: simultaneous output requires DC power (10-36 VDC) - AC power is not supported for simultaneous mode.
How do I wire the MSX Pro?
Four-position removable European-style terminal block accepts 16-26 AWG wire. Terminals are labeled VAC, VDC, COM, and VOUT. For 4-20 mA current output: connect 10-36 VDC supply to VDC and the current receiver to COM (2-wire loop). For 3-wire 0-5/0-10 VDC voltage output: use VDC + COM + VOUT with 17-36 VDC supply, OR VAC + COM + VOUT with 21.6-33 VAC isolated supply. For simultaneous output: use VDC + COM + VOUT with separate wire leads joined only at the transmitter. Tighten the cable gland to maintain NEMA 4X rating, and remove the LCD before wiring if equipped (pull straight up off the PCB pins, reinstall after wiring).
Can I add a display to this transmitter?
Yes. Two options: (1) Order the matching LCD variant MSXP-W20-PA-LCD at the same range, direction, and mount type. (2) Order the LCD as a separate accessory - the A-MSXP-LCD replacement display drops onto the PCB pins inside the existing housing without rewiring. Note that without the LCD, the menu-driven configuration features (alarm limits, K-factor, duct area for velocity/flow modes) are not accessible - you can still set range, direction, response time, and output via the internal DIP switches, but the menu functions require the display.
How do I install the wall mount version?
Mount the transmitter on a vertical wall or panel using the wall-mount bracket - the four mounting holes are labeled on the bracket. Use #8 x 1/2 in pan-head sheet metal screws (not included) suited to the mounting surface. Dwyer recommends mounting with pressure ports facing DOWN to prevent moisture from entering either the pressure ports or the cable entry. Pressure sensor measurement is non-position-sensitive so the unit will read correctly in any orientation, but the down-facing orientation protects the unit from condensation. For in-duct installations, see the Universal mount variant (MSXP-U) which includes the duct probe.
How do I switch to velocity or flow output mode?
DIP Switch 3 toggles between pressure mode (OFF) and velocity/flow mode (ON). In velocity/flow mode, DIP Switches 1 and 2 select the units (FPM, m/s, CFM, or m3/hr), and DIP Switches 7 and 8 select the maximum range output (see the P-MSXP-A install manual for the full range tables - e.g., Range 2 in velocity mode can output up to 4000 FPM / 20 m/s). The transmitter handles the square-root extraction internally; you don't need a separate signal conditioner. For CFM/m3/hr (flow) mode, the K-factor (0.001-9.999) and duct area (0.125-25 sq ft or 0.01161-2.32258 sq m) are entered through the LCD menu - these settings are not accessible without the optional LCD display.
Brand:
Dwyer
Manufacturer:
Dwyer Instruments LLC (DwyerOmega)
Series:
Series MSX Pro Magnesense
Product Type:
Differential Pressure Transmitter
Pressure Range Full Scale:
+/-0.5 in WC (125 Pa / 12.5 mm WC)
Range Code:
Range 0
Direction:
Bidirectional
Mount Type:
Wall Mount
Selectable Sub-Ranges (in WC):
0.05 in WC, 0.1 in WC, 0.25 in WC, 0.5 in WC
Selectable Sub-Ranges (Pa Low Set):
15 Pa, 25 Pa, 40 Pa, 50 Pa
Selectable Sub-Ranges (Pa High Set):
60 Pa, 75 Pa, 100 Pa, 125 Pa
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