Airflow measurement accurate to 0.19% uncertainty. Lifetime calibration. No annual service.
NJK Precision's airflow measurement stations use a patented dual-chamber airfoil design to normalize turbulent airflow before measurement — delivering NIST-certified accuracy down to 50 FPM in applications where traditional stations fail, drift, or simply can't be placed.
The Problem With Traditional Airflow Measurement
Most airflow measurement stations depend on laminar, uniform airflow. Real ductwork doesn't cooperate. Turbulence near elbows, dampers, transitions, and fans introduces significant measurement error. ASHRAE Standard 111 typically requires stations to be placed multiple duct diameters away from any disturbance — which often means the ideal measurement location simply isn't available.
Multi-probe traverse arrays have a separate problem: when any individual sensor degrades, the aggregate reading drifts — and there's no way to identify which probe is the source without taking the system apart. Annual recalibration becomes a line item that never fully solves the underlying problem.
The gap between what a system reports and what is actually moving through the ductwork is the gap between code compliance and a compliance liability.
Placement Restrictions
ASHRAE 111 requires multiple duct diameters of straight run — space that often doesn't exist in real buildings.
Aggregate Drift
Multi-probe arrays average across all sensors. When one degrades, the whole reading drifts — invisibly.
Annual Recalibration
A recurring cost that doesn't fix the underlying accuracy problem — it just resets the clock.
Compliance Liability
Inaccurate OA measurement means DCV control is wrong. What the BAS reports and what's actually happening diverge.
How NJK Precision Solves It
NJK's core patent is a dual-chambered airfoil design that normalizes turbulent airflow before measurement occurs. Turbulent air enters the inlet chamber. The airfoil structure redistributes and normalizes that airflow before it reaches the sensor — eliminating the measurement error that turbulence causes in probe-based systems.
The normalized airflow passes through a single Mass Air Flow Thin Film sensing probe using advanced Thermal Dispersion Technology — the same technology used in high-accuracy laboratory and automotive applications for decades.
Each sensing probe is individually calibrated on a primary NIST-certified airflow testing stand to an uncertainty of 0.19% at 95% confidence — across the full measurement range from maximum flow to minimum flow, not just at design conditions.
Minimum measurable velocity: 50 FPM. Most competing systems cannot accurately measure below 300–500 FPM. Low-flow accuracy is what makes demand-controlled ventilation work correctly at partial load and reduced fan speeds.
Why Single Sensor Matters
Multi-probe airflow stations average readings across multiple sensors. When sensors are new and calibrated, averaging can improve accuracy. Over time, individual sensors degrade at different rates — the average drifts, and there is no way to identify the source of error without dismantling the station.
NJK uses one sensor. The reading comes from one calibrated probe. If that probe is accurate — and it is, calibrated to 0.19% uncertainty on a NIST-certified stand before it leaves the factory — the measurement is accurate. No aggregate drift. No degrading sensor contaminating the average.
One sensor. Lifetime calibration. No drift.
Minimal inspection and cleaning. No annual recalibration. No probe replacement schedule. No system downtime to identify drift sources.
Two Products. One Technology.
Both the Flow Frame and the Damper Louver Solution are built on the same foundation — the same patented dual-chamber airfoil design, the same single Thin Film sensing probe, and the same NIST-certified calibration to 0.19% uncertainty. The difference is the frame geometry, engineered specifically for the environment each product serves. TPI handles product selection — contact us with your application and we'll confirm the right fit.
Patented Dual-Chamber Airfoil
Normalizes turbulent airflow before it reaches the sensor — enabling accurate measurement where traditional stations require multiple duct diameters of straight approach.
Single Thin Film Sensing Probe
One sensor. Calibrated to 0.19% uncertainty across the full flow range. No aggregate drift from degrading probes.
Plug-and-Play Flow Measuring Module
Field-removable and replaceable without special tools or system recalibration. Calibration transfers with the module.
Lifetime Calibration
No annual recalibration required. Both products maintain factory calibration accuracy throughout their service life.
Flow Frame (FF)
Optimized for ducted HVAC applications. The FF frame geometry runs parallel to airflow and installs inside the duct run, connecting to an externally mounted Signal Processing Unit.
Supply, return, exhaust, and outdoor air duct applications with consistent approach conditions.
Damper Louver Solution (DLS)
Optimized for damper and louver applications. The DLS adds a U-frame with active airfoil uprights running perpendicular to damper blades, dual-pressure-isolating end caps, and dual chamber corners — normalizing the turbulence and velocity variation that damper position creates.
OA intake dampers, louver face-mount applications, locations without straight duct approach, and large openings.
Same sensor. Same calibration. Same accuracy. Different frame for a different job.
Not sure which fits your application? Contact TPI and we'll confirm the right product and handle submittal documentation.
Where NJK Precision Is Specified
Outdoor Air Intake Dampers
Primary OA measurement for ASHRAE 62.1 compliance and demand-controlled ventilation.
AHU Face-Mount
Total supply or return airflow at the air handler opening.
Makeup Air Units
Precise flow control for 100% outdoor air systems in commercial kitchens, laboratories, and manufacturing.
Laboratory Exhaust
Accurate exhaust flow for fume hood pressurization and room pressure differential control.
Demand-Controlled Ventilation
Accurate low-flow signal for CO₂-based DCV at partial load.
Cleanrooms
Where accuracy below 300 FPM is required and sensor drift is not acceptable.
Tell us about your project. We'll find the right solution.
TPI handles sizing and local technical support for all NJK Precision products. Submit your project details and we'll respond with sizing recommendations and pricing.
NJK Precision — Literature & Resources
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