IoT Long Range Wireless Precision Pressure Sensor — Bidirectional / Differential

01Overview

The NCD IoT Long Range Wireless Precision Pressure Sensor measures the pressure difference between two ports and reports it — positive or negative — along with on-board temperature. It is built around a high-resolution, medical-grade digital differential pressure sensing element that uses a thermal, flow-through measuring principle rather than a mechanical diaphragm. That gives it two properties that matter at very low pressures: it resolves changes of a few thousandths of a pascal — a smallest step of 0.004 Pa on the ±0.5 inH₂O range — and it has essentially no offset drift — so it does not need periodic re-zeroing to stay accurate.

Its span is deliberately narrow — ±0.5 inH₂O (±125 Pa) or ±2 inH₂O (±500 Pa), selected at time of order — which is what makes it the right instrument for the lowest-pressure jobs: cleanroom, isolation-room and laboratory pressurization, fume-hood and containment verification, building pressure envelopes, HVAC filter loading, VAV control, heat recovery, and air velocity or flow when paired with a pitot tube. Because it is bidirectional, it resolves pressure in both directions across the two ports, so a reversed or negative differential reads as a negative value. Readings are sampled at a user-defined interval and transmitted over a long-range wireless mesh network to an Atrium IIoT Gateway.

The sensor ships with one of three wireless communication modules. Choose the frequency band that matches your gateway and region — the sensor core, firmware, and Atrium integration are identical across all three. The 900 MHz and 868 MHz options run on NCD’s sub-GHz wireless mesh network, which cuts through industrial noise and interference for secure, long-range communication.

What’s in the Box

• IoT Long Range Wireless Precision Pressure Sensor with a D-cell (LR20) lithium battery and integrated supercapacitor installed
• Wireless communication module per your selection (900 MHz, 868 MHz, or 2.4 GHz)
• Two barbed pressure nozzles, plus a short length of correctly sized flexible tubing
• External antenna with RP-SMA connector and a U.FL-to-RP-SMA pigtail adapter, supplied with the wireless module (optional high-gain antenna and RP-SMA extension cables available separately)

02Specifications

Full technical specifications for the Precision Bidirectional Differential Pressure Sensor (SKU PR55-24). Pressure and temperature figures are the sensing element’s own rated performance, verified against the element manufacturer’s datasheet.

Pressure Range Options

Select the range at time of order to match the job. The lower range gives four times the resolution and is the one to pick for room-pressure and containment work; the wider range covers duct and filter differentials that would saturate the lower one. Both use the same element technology, enclosure, firmware, and Atrium integration — only the span differs.

Reading the Range in Your Preferred Units

This sensor’s span is most often quoted in inches of water (inH₂O), the unit North American HVAC and room-pressure work uses. Atrium logs the reading in pascals by default; Section 7 shows how to have Atrium display and alert in inH₂O instead.

Pressure Ports & Media Compatibility

The sensor has two pressure ports. The differential reading is the pressure at Port 2 relative to Port 1, so a higher pressure on Port 2 reads positive and a higher pressure on Port 1 reads negative. Unlike diaphragm-based differential pressure sensors, this element’s media limits are the same on both ports — there is no “wet side.”

03Prerequisites

Before installing this sensor, make sure you have the following in place.

Hardware Required

• NCD Atrium IIoT Gateway — powered on and connected to your local network
• Precision Bidirectional Differential Pressure Sensor (this unit) with the wireless module and antenna installed
• Flexible tubing of roughly 3/16″ (4.8 mm) or 4 mm inside diameter to connect Port 1 and Port 2 to your process taps. A short length is supplied with the sensor; source additional tubing to suit the run
• A mounting point on or near the monitored space — a flat wall surface, or a ferrous surface if using the optional magnetic mounting hardware

Software / Network

• A current version of Atrium running on your gateway
• A computer or mobile device on the same local network as the gateway
• A modern web browser (Chrome recommended)

04Mounting & Installation

At this sensor’s resolution, installation quality is the limiting factor on accuracy. An instrument resolving thousandths of a pascal will faithfully report the pressure at the end of your tubing — including any error the tubing introduces. Keep runs short, keep them dry, and keep both ports clear.

Powering On

1. 1
   Set the power switch

   The unit ships with a D-cell (LR20) lithium battery installed. Open the enclosure and slide the 3-position power switch to Battery Power, or to External Power if you are powering the sensor from the barrel-connector supply (external power runs with battery backup). The Off position disconnects power for storage.
2. 2
   Confirm power

   Activate the CFG magnetic switch with a magnet — or, with the enclosure open, briefly press the on-board CFG button. The TEST LED illuminates, confirming the board has power.

Connecting the Pressure Ports

• Identify the ports. The differential reading is Port 2 relative to Port 1. For a room-pressurization measurement, connect Port 2 to the controlled space and Port 1 to the reference space, so a correctly pressurized room reads positive. For filter or restriction monitoring, connect Port 2 upstream and Port 1 downstream so a rising differential reads positive.
• Use correctly sized tubing, kept short and dry. The barbs take flexible tubing of roughly 3/16″ (4.8 mm) or 4 mm inside diameter — it should stretch slightly over the Ø5.2 mm retaining ridge and grip. Tubing with a larger bore (1/4″ and up) slips on loosely and will leak or fall off. Push the tubing fully onto the nozzles and route it so any condensate drains away from the sensor, never toward it. Avoid low spots that can trap moisture — a slug of water in the tubing will both corrupt the reading and put liquid at the port.
• Protect the ports from particulate. The element’s internal flow channel is small. In dusty air, take the tap from a clean location or fit an appropriate in-line filter; a partially blocked port produces a reading that looks plausible but is wrong.
• Let it settle before you trust a reading. After connecting, give the tubing time to equalize and the sensor time to reach ambient temperature before recording a baseline.

Mounting the Sensor

The impact-resistant, UV-stabilized polycarbonate enclosure measures approximately 4.53 × 3.56 × 2.26 in (115 × 90 × 57 mm) and carries two molded-on mounting flanges with keyhole slots for surface mounting. The removable cover seals against a silicone perimeter gasket for its IP65 rating, and lifts off via the four corner screws for battery access.

• Wall mount: Fasten the enclosure to a flat surface through the keyhole slots in the two molded-on mounting flanges. Orient it so the ports and tubing face down or sideways to discourage moisture from collecting in the tubing.
• Magnetic mount: With the optional magnetic mounting hardware, attach the enclosure to a clean, flat ferrous surface for tool-free placement.
• Keep it out of the airstream. Mount the enclosure in still air where practical. Direct airflow, sunlight, or a nearby heat source will move the temperature reading and can shift the pressure span slightly.

05Pairing with Atrium

Once powered on, the sensor transmits over its long-range wireless mesh and the gateway begins hearing it. New sensors are held pending (blacklisted) until you whitelist them through the Sensor Details wizard — data is not logged until a sensor is whitelisted. The wizard walks you through naming and whitelisting each detected sensor.

1. 1
   Power on and place the sensor

   Confirm the sensor is powered (activate the CFG magnetic switch — or press the CFG button — and check that the TEST LED illuminates) and that the ports are connected. Within one transmission interval — up to 10 minutes at the default 600-second Delay — the gateway will begin receiving its transmissions.
2. 2
   Open Atrium and go to Sensors

   Navigate to your gateway’s local address (e.g. http://ncd-[last-4-of-MAC].local) and click Sensors in the top navigation. A banner shows “X sensors need setup” with detected sensors grouped by type. Your unit appears as 20 – Wireless High Precision Pressure Sensor.
3. 3
   Open the Sensor Details wizard

   Click the sensor in the banner (or in the Sensors table) to open the Sensor Details wizard. New sensors start pending (blacklisted) — completing the wizard whitelists the sensor so Atrium begins logging its data.
4. 4
   Enter details and save

   Give the sensor a Sensor Name, Asset, and Location (see Section 6). Use Save to whitelist and finish, Save & Next to move to the next pending sensor, or Skip to leave a sensor pending for now.
5. 5
   Confirm it is reporting

   The whitelisted sensor now appears in the Sensors table with a recent Last Heard timestamp. Open its Dashboard to confirm live pressure and temperature data.

06Sensor Meta

The Sensor Meta tab controls how Atrium identifies and tracks this sensor. Access it via Sensors → [your sensor] → Configure → Sensor Meta.

07Metric Configuration

The Metrics tab lets you configure conversion formulas, units, custom labels, and dashboard visibility for each data channel. Access it via Configure → Metrics. This sensor reports differential pressure and temperature, plus battery and packet-metadata channels.

Custom Conversion Formulas

Each metric supports a custom conversion formula using value as the variable name. Leave the formula as value or blank to display raw data in pascals. Examples for converting the pressure reading to other units:

value / 249.0889      // Convert pressure from Pa to inches of water (inH2O)
value / 100           // Convert pressure from Pa to mbar
value / 1000          // Convert pressure from Pa to kPa
value / 6894.757      // Convert pressure from Pa to PSI
value / 133.3224      // Convert pressure from Pa to mmHg (torr)

Custom Labels & Visibility

Each metric can be assigned a Custom Label that replaces the default metric name throughout Atrium. Unchecking Visible on Dashboard hides that metric’s card and chart without deleting data — useful for focusing a dashboard on the pressure channel that matters for a given space.

08Hardware Settings

Hardware settings control the sensor’s on-board configuration — transmission interval and network addressing. Changes are staged in Atrium and pushed to the sensor on its next configuration check-in. Access via Configure → Sensor Configuration.

Key Configuration Parameters

Choosing a Transmission Interval

Pressure envelopes can fail quickly. If you are monitoring a cleanroom, isolation room, or fume hood where a lost differential matters within minutes, a shorter Delay is worth the battery cost — or run the sensor on external power and sample as often as you like. For slow-moving trends like filter loading, the 600-second default is generally more than enough.

1. 1
   Go to Sensor Configuration

   Navigate to Sensors → [your sensor] → Configure → Sensor Configuration.
2. 2
   Update the Delay value

   Set your desired transmission interval (Delay) in seconds. Shorter intervals give more frequent readings at the cost of battery life.
3. 3
   Click Save Hardware Settings

   The new values are staged and pushed to the sensor on its next configuration check-in — wait up to one transmission interval, or trigger the RESET magnetic switch (or press the RESET button) to sync immediately.
4. 4
   Update the Report Interval in Sensor Meta

   Update the Report Interval on the Sensor Meta tab to match your new Delay value so offline detection stays accurate.

Battery Life

The sensor delivers up to 5 years of battery life. Actual life depends on your configuration — a shorter Delay (more frequent transmissions) draws more power. To estimate battery life for your exact settings, use NCD’s battery life calculator. For continuous high-rate monitoring, run the sensor on external power.

09Temperature Units

This sensor reports on-board temperature alongside its pressure metric. Atrium provides a global temperature display unit setting that controls how temperature readings appear across the entire interface — all sensors, dashboards, alerts, and reports.

1. 1
   Open Gateway Settings

   Click Settings in the top navigation to open Gateway Configuration.
2. 2
   Select Temperature Display Unit

   Under Temperature Display Unit, toggle between °C and °F. This applies immediately to all temperature readings across Atrium.
3. 3
   Save Configuration

   Click Save Configuration at the bottom of the page to apply the change.

10Sensor Dashboard

The Sensor Dashboard provides a real-time and historical view of all data from this sensor. Access it by clicking the sensor in the Sensors list and selecting Dashboard.

Live Metrics

Time Range & Charts

Use the time range selector to view historical data for the last hour, 6 hours, 24 hours, 7 days, or 30 days. A custom date/time range is also available. Each metric has its own interactive chart — drag to zoom into a time window, double-click to reset. At this resolution the pressure trace is genuinely informative: a room’s pressure envelope shows its daily cycle as doors open and air handlers stage, and a slow downward drift over days is usually the first sign of a loading filter or a failing damper.

Mesh Route Map

Click View Map in the Mesh Route Map panel to visualize how this sensor’s data routes through the wireless mesh to reach the gateway. Useful for diagnosing signal path issues in multi-sensor deployments.

Interactive Preview

The panel below simulates the Atrium Sensor Dashboard for this Precision Pressure sensor. Data updates every 5 seconds to demonstrate the live monitoring experience.

11Setting Alerts

Atrium uses a Triggers & Actions model for alerting. A Trigger defines the threshold condition on a metric. An Action defines what happens when all assigned triggers fire. Navigate to Alerts in the top navigation (the page is titled Alerts & Actions) to configure.

Creating a Trigger

1. 1
   Go to Alerts → Triggers

   Click + New Trigger to open the Create Trigger form.
2. 2
   Configure the trigger

   Select the Device, Metric (e.g. pressure or temperature), Condition (Above or Below), and Threshold value. Enter the threshold in pascals unless you have applied a conversion formula in Metric Configuration. The Reset At column sets the value the metric must return to before the trigger can fire again — this hysteresis prevents repeated firing when the value oscillates near the threshold. Click Create Trigger.

Creating an Action

1. 1
   Go to Alerts → Actions

   Click + New Action. Actions link one or more triggers to a response — when all assigned triggers fire simultaneously, the action executes.
2. 2
   Assign triggers and configure the response

   Select the trigger(s) to watch and configure the response. Atrium supports email notifications and relay output actions (to drive an external relay, e.g. to sound a local alarm or signal a building management system). Email must be configured in Settings → Gateway Configuration for email actions to work.

12Exporting Data

All sensor data can be exported to CSV directly from the Sensor Dashboard for use in spreadsheets, reporting tools, or analysis software.

1. 1
   Open the Sensor Dashboard

   Navigate to the sensor and click Dashboard.
2. 2
   Select a time range

   Choose the time range you want to export using the selector at the top of the dashboard.
3. 3
   Click “CSV” on the desired metric

   Each metric chart has a CSV download button. Click it to download a timestamped CSV of that metric’s data for the selected time range. The exported pressure column is in pascals — or in your converted unit if you set a formula in Metric Configuration.

13Product Notes

Reference information for ordering and accessories.

Choosing Between NCD’s Differential Pressure Sensors

NCD offers more than one bidirectional differential pressure sensor, and they are not interchangeable. Pick by the span you need to measure and by whether liquid is involved.

14Troubleshooting

Common issues and their solutions.

Sensor not appearing in Atrium

• Confirm the sensor is powered — the power switch is set to Battery Power (or External Power), and pressing the CFG button lights the TEST LED.
• Verify the sensor’s wireless frequency (900/868 MHz or 2.4 GHz) matches the gateway’s radio.
• Verify the sensor’s Network ID matches the gateway’s Network ID (default 7fff). If the unit was left in Configuration Mode it uses 7bcd instead and will not report.
• Confirm the antenna is attached to the RP-SMA connector and the pigtail is seated on the wireless module.
• Move the sensor closer to the gateway to rule out range issues — test within 3 ft (1 m) first.
• Check that the Atrium gateway is powered on and connected to your network.

Sensor showing as Offline in Atrium

• Verify the Report Interval in Sensor Meta matches the Delay in Sensor Hardware Settings (both default to 600 seconds).
• Check the battery_pct on the last received reading — replace the D-cell battery if low.
• Check the RSSI value — remember higher numbers mean a weaker signal. Readings consistently above 75 dBm indicate marginal signal; reposition the sensor or gateway, add a high-gain antenna, or add a repeater node.

Pressure reading looks wrong

• Value is far larger or smaller than expected: check the unit before you check the sensor. This model reports pascals — a reading of 60 is 60 Pa (about 0.24 inH₂O), not 60 PSI. Also confirm no leftover conversion formula is applied in Metric Configuration.
• Reading pinned at the top or bottom of scale: the applied differential exceeds your unit’s range (±125 Pa or ±500 Pa, per the option ordered). This is an ultra-low-range instrument; a differential that saturates it needs a PSI-ranged sensor instead (see Section 13).
• Reading stuck, sluggish, or near zero: check for a clogged, kinked, or disconnected tube. The element’s flow channel is small, so dust or a droplet can block it. Confirm both nozzles are clear and the tubing is seated.
• Sign is reversed (negative when you expect positive): the ports are swapped. The reading is Port 2 relative to Port 1 — connect the higher-pressure tap to Port 2.
• Reading is noisy or wanders: long tubing runs, turbulence at the tap, or air moving across the enclosure all show up at this resolution. Shorten the tubing, move the tap to a less turbulent location, and keep the sensor out of direct airflow. Give the unit time to reach ambient temperature after installation.
• Reading never returns to zero at no-flow: unlike diaphragm sensors this element holds its zero to better than 0.05 Pa per year, so a persistent offset usually means a real residual pressure, a partially blocked port, or liquid in a tube — not a sensor that needs re-zeroing.
• Suspected liquid ingress: disconnect the tubing and stop using the sensor for measurement. Liquid in the flow channel damages the element and its readings should not be trusted afterward.

Hardware settings not updating on sensor

• Settings are staged and applied on the sensor’s next configuration check-in — wait one full transmission interval (up to 10 minutes at the default 600-second Delay) after saving.
• To apply changes immediately, press the RESET button, which opens a configuration window on boot.
• Confirm the sensor is actively transmitting by checking the Last Heard timestamp on the dashboard.

15Factory Reset

A factory reset restores the sensor’s wireless module to default settings. This is useful if the sensor is not being detected by a gateway, or if you are redeploying it to a new network. The magnetic switch method is recommended — no disassembly required. Reset behavior is governed by how long the CFG switch is held after a RESET.

Option A — Magnetic Switches (no disassembly)

1. 1
   Trigger the RESET switch

   Hold a magnet near the RESET magnetic switch, then move it away.
2. 2
   Wait 1 second

   Allow approximately 1 second before proceeding.
3. 3
   Hold the CFG switch for more than 15 seconds

   Hold the magnet near the CFG magnetic switch for approximately 20 seconds, then move it away. The hold must exceed 15 seconds to trigger a factory reset — a shorter hold only enters Configuration Mode.
4. 4
   Wait 3–5 seconds

   Allow 3–5 seconds for the reset to complete. The sensor is now reset to defaults and in Configuration Mode.
5. 5
   Trigger the RESET switch again

   Hold the magnet near the RESET switch once more, then move it away. This returns the sensor to normal Run Mode. Re-pair it in Atrium.

Option B — Physical Buttons (requires opening enclosure)

1. 1
   Open the enclosure

   Remove the cover to access the PCB, and locate the RESET and CFG buttons and the TEST LED.
2. 2
   Press and release the RESET button

   Press and release the RESET button on the PCB.
3. 3
   Wait 1 second, then hold CFG for more than 15 seconds

   Wait approximately 1 second, then press and hold the CFG button for approximately 20 seconds. The hold must exceed 15 seconds to trigger a factory reset. Release the button when done.
4. 4
   Wait 3–5 seconds

   Allow 3–5 seconds for the reset to complete. The sensor is now reset to defaults and in Configuration Mode.
5. 5
   Press RESET, then close the enclosure

   Press and release the RESET button once more to return the sensor to normal Run Mode, then re-seal the enclosure and re-pair it in Atrium.