The ACI A/DLP-D50-W-B-N-B-1-A-0P-S is part of ACI's DLP Series Differential Low Pressure Transmitter family - a factory-calibrated, custom-ranged variant configured for a -0.5 to +0.5 inch WC bidirectional range with a 4-20 mA output (2-wire loop powered (or 3-wire VAC powered)) and +/-0.25% FSO accuracy. The DLP uses a piezoresistive silicon sensing element with a hinged enclosure cover and integrated locking tab for easy access to the zero function. This SKU has a sealed cover (no LCD - this variant is intended for behind-panel or remote installation). A 7" aluminum duct-static pitot tube (A/PT-DLP) ships with this SKU - it threads into the back of the enclosure for direct duct-static measurement without separate pickup ports. This unit is factory-calibrated with NIST-traceable equipment but ships without a printed certificate. If your project requires documented calibration, see the matching variants with 3P or 5P NIST suffix. Made in USA by ACI in Middleton, Wisconsin.
This range is best suited for low-pressure HVAC applications: building static pressure, room-to-room pressure differentials, filter loading on residential and light commercial systems, and cleanroom envelope pressure measurements. Bidirectional mode (output centered at mid-scale: 12 mA, 2.5 V, or 5 V at 0 differential) is required when flow can reverse - reversible-flow systems, makeup-air systems with mode switching, or balance work. Per ACI's published applications: building and duct static pressure, filter monitoring, air flow measurement, and process control. This is a factory-calibrated custom-range SKU - the DIP switches are set at the factory and cannot be field-adjusted (see I0000977 installation manual). If your application needs to switch between ranges in the field, see the legacy multi-range catalog SKUs (A/DLP-001, A/DLP-010, A/DLP-040 in their standard configurations).
Key Features
This DLP is factory-calibrated to the -0.5 to +0.5 inch WC range using NIST-traceable equipment - DIP switches are set at the factory and the span calibration is locked. The unit ships ready to install with full-scale output across your specified range, giving you the best resolution and accuracy at the working pressure of your application.
A piezoresistive silicon sensing element senses differential pressure and provides a linear analog output proportional to the specified range. Silicon technology provides excellent long-term stability and minimal warmup shift versus older diaphragm-based designs.
4-20 mA current output, 2-wire loop-powered (16-36 VDC at 250 ohm load, 22-36 VDC at 500 ohm load) or 3-wire VAC-powered (24 VAC +/-10%). Output is limited to 21.4 mA maximum. Current output is preferred for long cable runs or noisy environments near VFDs.
Accuracy specification includes linearity, hysteresis, and repeatability at 71 deg F (21.5 deg C) typical. Thermal effects: +/-0.067% FSO per deg F (0.12% FSO per deg C) relative to 71 deg F. This is the enhanced +/-0.25% accuracy class - useful for applications where you need tighter control limits or audit-grade documentation.
An on-board pushbutton ZERO performs in-place offset calibration. Procedure: ensure no pressure at HI or LO fittings (or connect a loop between them), then press and hold ZERO for more than 3 seconds. Long-term drift is primarily an offset shift (not a span shift) - periodic re-zeroing eliminates drift without service interruption.
This SKU ships with the A/PT-DLP DLP-specific aluminum duct-static pitot tube (7" total length, 6.75" insertion). The pitot threads directly into the back of the DLP enclosure with the included rubber washer for a sealed connection. When the pitot is installed, the silicone tubing on the High Pressure (H) barb is removed and re-routed to the pitot barb fitting - leaving the H barb open to atmosphere as the reference.
Finger-pushbutton (spring) terminal blocks accept 16-24 AWG wire - no screwdriver required for routine connections. The enclosure ships with a watertight cordgrip installed; for 1/2" NPT conduit, remove the cordgrip and install your conduit fitting. ACI recommends shielded cable with the shield grounded only at the controller end.
Proof pressure of 270 inch WC (67.2 kPa) and burst pressure of 415 inch WC (103.3 kPa) - well above this SKU's operating range. Tolerates transient overpressure from duct damper slams, fan start-up surges, and commissioning test pressures without sensor damage. Media must be non-corrosive, non-ionic gases (dry air or inert gases).
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Active differential low pressure transmitter, factory-calibrated single range |
| Sensing Element | Piezoresistive silicon |
| Measured Value | Differential pressure (HI - LO ports) |
| Pressure Range (Factory Set) | -0.5 to +0.5 inch WC (Bidirectional) - DIP switches locked at factory |
| Output Signal | 4-20 mA - 2-wire loop powered (or 3-wire VAC powered) |
| Accuracy | +/-0.25% FSO (includes linearity, hysteresis, repeatability at 71 deg F) |
| Thermal Effects | +/-0.067% FSO per deg F (0.12% FSO per deg C) relative to 71 deg F |
| Response Time (0-100% FSO) | 4 seconds |
| Output Update Rate | 0.5 second intervals |
| Zero Function | Pushbutton ZERO (hold >3 sec) |
| Display | No LCD |
| Proof Pressure | 270 inch WC (67.2 kPa) |
| Burst Pressure | 415 inch WC (103.3 kPa) |
| Power Supply | 16-36 VDC (250 ohm load) or 22-36 VDC (500 ohm load), or 24 VAC +/-10% 50/60 Hz |
| Supply Current | 24 mA minimum (0.83 VA) |
| Operating Temperature | -4 to 185 deg F (-20 to 85 deg C) |
| Compensated Temperature Range | 32 to 122 deg F (0 to 50 deg C) |
| Storage Temperature | -22 to 185 deg F (-30 to 85 deg C) |
| Operating Humidity | 10-95% RH non-condensing |
| Media Compatibility | Non-corrosive, non-ionic gases (dry air, inert gases) |
| Pressure Fitting | Nickel-plated brass or stainless steel push-on, accepts 1/4" OD x 0.170" ID poly tubing |
| Enclosure | Flame-retardant polycarbonate, UL94-5VA |
| Conduit | Watertight cordgrip installed; accepts 1/2" NPT conduit when cordgrip removed |
| Wiring | Finger pushbutton (spring) terminal blocks, accepts 16-24 AWG |
| Dimensions | 5.56 x 4.35 x 2.25 in (141.29 x 110.43 x 57.24 mm); 6.21 in deep with cordgrip |
| Weight | 0.80 lb (0.363 kg) |
| Optional Accessories | Pitot Tube Included |
| NIST Calibration | No NIST Certificate - Factory NIST-traceable calibration |
| Approvals | CE, RoHS2, WEEE, REACH |
| Manufacturer | ACI (Automation Components, Inc.) - Middleton, WI USA |
| Manufacturer Part Number | A/DLP-D50-W-B-N-B-1-A-0P-S |
| Warranty | 5-Year ACI Limited Warranty |
What's In the Box
- DLP transmitter, factory-calibrated to the specified range
- Watertight cordgrip pre-installed (accepts 1/2" NPT conduit when removed)
- Two (2) #8 x 3/4" self-drilling panel-mount screws
- Installation & Operation Instructions (ACI document I0000977)
- A/PT-DLP 7" aluminum duct-static pitot tube with rubber sealing washer
- Pressure-sense tubing (medical-grade clear PVC, 0.17" ID x 0.25" OD) - A/10' TUBE, A/20' TUBE, A/50' TUBE, A/100' TUBE
- Additional pitot tubes if needed for multi-point measurement - PT 3", PT 5.2", PT 7.5", PT 9.7" (foam gasket); SPT-3.5", SPT-8.0" (static, flat tip); VPT, VPT-8" (velocity, pointed tip)
- DIN rail clip (if rail-mounting) - A/DRC-DLP (35 mm)
- Pickup ports for room/wall pressure taps: A/SP-PUP, A/R-PUP, A/R2-PUP, A/O-PUP-H, A/O-PUP-V
- Power supply transformer and BAS controller wiring
- Shielded cable (ACI recommends 16-24 AWG twisted pair shielded)
Documentation
Frequently Asked Questions
What does the A/DLP-D50-W-B-N-B-1-A-0P-S measure and output?
It measures differential air pressure in the -0.5 to +0.5 inch WC range (bidirectional) and outputs a linear 4-20 mA analog signal proportional to the pressure. Accuracy is +/-0.25% FSO including linearity, hysteresis, and repeatability. The DLP is intended for HVAC and process applications using dry air or other non-corrosive, non-ionic gases - not liquids, refrigerants, or corrosive vapors.
Can I change the range or output mode in the field?
No - this is a custom-calibrated DLP. The range and output mode are set at the factory and the DIP switches are locked (per ACI's I0000977 installation manual: "This is a custom calibrated DLP and the output span switches CANNOT be adjusted"). If you need a field-selectable multi-range DLP, see the legacy catalog SKUs (A/DLP-001-W-U-N-A-0, A/DLP-010-W-U-N-A-0, A/DLP-040-W-U-N-A-0 and their LCD variants) - those ship with 8 selectable ranges per unit.
When do I need bidirectional mode?
This SKU is bidirectional - required when the differential pressure can swing both positive and negative across zero. In bidirectional mode, 0 differential = 50% of output range (12 mA, 2.5 V, or 5 V depending on output type). For one-direction-only applications, see the matching unidirectional variants for full range resolution.
When and how should I zero the device?
Zero on initial installation, after re-positioning, and any time the unit reads a non-zero offset with no pressure applied. Procedure: (1) Remove the tubing from the HI and/or LO pressure fittings (or short them together to neutralize external pressure). (2) Press and hold the ZERO button for more than 3 seconds, then release. For LCD variants, the AUTOZERO icon will appear on the screen during zero mode and flash twice on successful completion. The Span calibration is digital and factory-set; units requiring Span re-calibration must be returned to ACI.
Does this come with a NIST certificate?
No - this is the standard 0P (no NIST certificate) variant. The DLP is factory-calibrated using NIST-traceable equipment, but no printed certificate is shipped. If your project requires a documented certificate of calibration, see the 3P (3-point at 10%/50%/90% FSO) or 5P (5-point at 10%/30%/50%/70%/90% FSO) variants of the same configuration.
What accessories do I need for installation?
Required: pressure-sense tubing (0.25" OD x 0.17" ID medical-grade PVC - A/10' TUBE, A/20' TUBE, A/50' TUBE, A/100' TUBE), 16-24 AWG shielded cable, and a 24 VAC or 15-36 VDC power supply. Application-dependent: pitot tube for direct duct-static measurement - the DLP-specific A/PT-DLP (7") threads into the back of the enclosure, or use generic ACI pitots (PT 3", PT 5.2", PT 7.5", PT 9.7" with foam gaskets; SPT-3.5" / SPT-8.0" static; VPT / VPT-8" velocity). DIN rail clip for panel mounting: A/DRC-DLP (35 mm). Pickup ports for wall/room pressure taps: A/SP-PUP, A/R-PUP, A/R2-PUP, or outdoor weatherproof A/O-PUP-H / A/O-PUP-V. Keep tubing runs under 75 feet (23 meters).
Any tips for getting accurate readings on this ultra-low range?
Below 1 inch WC, several factors can swamp the signal: (1) Mount vertically with brass fittings pointing down - prevents condensation from affecting the sensor (horizontal mounting can cause a small zero shift). (2) Keep tubing runs short - long runs introduce lag. (3) Re-zero after installation and after temperature swings. (4) Avoid sharing the 24 VAC transformer with inductive loads (VFDs, relays, solenoids) - induced noise on the supply rail shows up as small offsets at these low ranges. (5) If 24 VDC or VAC power is shared with coils, add MOVs, Transorbs, or flyback diodes across each coil per ACI's installation guide.
How does the DLP compare to the MLP2?
Both are differential low-pressure transmitters using the same piezoresistive silicon sensing technology. DLP advantages: larger enclosure with hinged cover for easier zero/output access, optional 5-digit LCD display on the unit cover, watertight cordgrip for environmental sealing, factory-bundled Pitot/DIN rail accessory options, broader range coverage (up to 0-40" WC vs MLP2's 0-30" WC). MLP2 advantages: smaller compact form factor (designed for OEM/panel density), integrated DIN rail foot, lower price point. Choose DLP for applications needing the LCD, larger enclosure, or wider range options; choose MLP2 for OEM/panel-density installations.
What media can this sensor handle?
Dry air and inert non-conductive gases only: clean ambient air, nitrogen, argon, dry CO2. The DLP is NOT compatible with: liquids, refrigerants, corrosive gases (chlorine, ammonia, hydrogen sulfide, acid fumes), conductive gases, condensing moisture, or media containing particulates. Liquid contamination at the sensor diaphragm causes immediate damage and voids the warranty. For wet/wet differential pressure applications, see Senva PW30 or Belimo 22PDP series in the Liquid Pressure subcategory.
What's the warranty?
5-Year ACI Limited Warranty - covers manufacturing defects in materials and workmanship under normal use. Manufactured in Middleton, Wisconsin, USA. ZOT Supply is an authorized ACI distributor; warranty claims are processed directly with ACI. The full warranty terms are in the front of ACI's Sensors & Transmitters catalog.
- Series:
- DLP
- Pressure Range:
- -0.5 to +0.5 inch WC
- Range Class:
- Low
- Direction:
- Bidirectional
- Output Signal:
- 4-20 mA
- Accuracy:
- +/-0.25% FSO
- Display:
- No
- NIST Certificate:
- None
- Mounting:
- DIN Rail / Panel
- Made in USA:
- Yes
