01 //
The Problem
Your AirFeed™ reservoir fills with water. You know the device is running. But how much nitrogen is actually dissolved in there? Is it ready to apply? Is it enough for your tomatoes? Should you wait another day?
Right now, the answer is: you don't know. No consumer instrument exists to measure dissolved nitrogen in a small reservoir at the concentrations an atmospheric fixation device produces. Lab analyzers cost $5,000–$50,000. Aquarium test kits are manual, slow, and read once. Neither was designed for this use.
The NitrogenMeter™ is designed to solve this. Continuously. In the reservoir. In real time.
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How It Works
1
Ammonium Ion-Selective Electrode (ISE)
A nonactin ionophore membrane in contact with your reservoir liquid generates a millivolt potential proportional to dissolved ammonium ion (NH₄⁺) concentration. This is the same principle as a pH meter — but tuned specifically to ammonium at the 0–200 ppm range your AirFeed™ device produces. Design target measurement range: 0.5–200 ppm total ammoniacal nitrogen (TAN).
2
Temperature Compensation
A co-mounted thermistor measures reservoir temperature continuously. The onboard microcontroller applies the Nernst equation temperature correction in real time, so your reading is accurate whether the reservoir is cold on a winter morning or warm in an Arizona summer. Design target accuracy: ±10 ppm across 15–45°C ambient range.
3
Float-Integrated Level Sensing
A buoyant float element rides on the reservoir surface, connected by a pivot arm to a Hall-effect position sensor at the electrode mount. As your reservoir fills with nitrogen-rich liquid, the float rises and the sensor reports fill percentage. You see both nitrogen concentration and reservoir level on the same display — like a fuel gauge and fuel quality meter in one.
4
Plain-Language Output
The display shows ppm TAN, fill percentage, and a qualitative status: LOW → BUILDING → READY TO APPLY → DILUTE BEFORE USE. No chemistry degree required. You know when your water is ready and how much reservoir you have left.
03 //
Design Target Specifications
Design targets only. All specifications below are intended design targets. The NitrogenMeter™ is in development. Actual performance will be determined through prototype validation testing. Specifications subject to change.
Measurement Range
0.5–200 ppm
Total ammoniacal nitrogen (TAN)
Target Accuracy
±10 ppm
vs. ion chromatography reference
Operating Temp.
15–45°C
Nernst temperature compensation
Probe Diameter
⌀ 12mm
Reservoir cap mount
Sensing Principle
ISE + Float
Ammonium ion-selective electrode + Hall-effect position sensor
Output
LED + BLE
Local display + optional wireless to mobile app
Calibration Interval
30–90 days
Via calibration access port
Service Interval
6–12 months
ISE membrane replacement
Target Price
$79–$149
Consumer — design target
04 //
Three Sensing Approaches
The patent application (App. No. 64/090,362) covers three distinct sensing embodiments. Each addresses a different balance of cost, accuracy, and installation requirements.
Embodiment 1 — Primary
Ion-Selective Electrode (ISE)
Ammonium-selective membrane probe submerged in reservoir liquid. Most direct measurement of dissolved NH₄⁺. Paired with float element for simultaneous level sensing. Fastest path to prototype. Reference electrode co-housed in dual-barrel body.
Embodiment 2
Headspace Chemiresistive
Polyaniline (PANI) film mounted on reservoir cap interior, measuring NH₃ vapor in the headspace above the liquid. No submersion required. Henry's Law equilibrium converts vapor reading to liquid-phase TAN equivalent. Humidity-compensated via co-mounted capacitive sensor.
Embodiment 3
Wireless Data Transmission
Bluetooth Low Energy or 900MHz LPWAN module transmits TAN concentration and fill level to a paired mobile device. Companion app displays historical nitrogen accumulation trends, application threshold alerts, and performance logs over time.
05 //
The C & C Ecosystem
The NitrogenMeter™ is Product 6 in the C & C's Fertilizer ecosystem — the measurement layer that makes every other product more powerful.
🌿
AirFeed™
Passive nitrogen fixation device — the NitrogenMeter™ mounts directly into its reservoir cap
⚡
BoltBrew™
Solar plasma reactor — NitrogenMeter™ monitors output concentration in real time
🌿
AirFeed Complete™
Dual-mesh upgrade — sensor confirms mesh performance and service interval timing
🪨
AirFeed Pellet™
Slow-release nutrient puck — sensor confirms dissolution and nutrient availability
🫙
The Vessel™
Delivery container — fill it when the NitrogenMeter™ says READY
📊
NitrogenMeter™
You are here — the measurement instrument for the whole system
06 //
Intellectual Property
// Patent Pending — USPTO Provisional Application
Title: Integrated Nitrogen Compound Concentration Sensor for Atmospheric Fixation Reservoir Systems
Application No.: 64/090,362
Patent Center No.: 77418214
Confirmation No.: 3807
Filed: June 14, 2026
Non-Provisional Deadline: June 14, 2027
Inventor: Craig Mathew Hall
Assignee: HVOKC, LLC (Micro Entity)
Claims covered: ISE reservoir sensor, float-integrated level sensing, headspace chemiresistive sensing, wireless data transmission, combined dual-readout assembly
Patent Pending — App. No. 64/090,362. A provisional patent application does not confer the rights of an issued patent. Non-provisional application must be filed by June 14, 2027 to maintain priority. Verify filing status at patentcenter.uspto.gov ↗
Research or Licensing Inquiry
The NitrogenMeter™ is in development. If you are a researcher studying atmospheric nitrogen fixation, an agricultural instrument manufacturer, or a university lab interested in the sensor platform for research applications — reach out directly.
Contact Craig → erm@hvokc.com
Important notices: All product specifications on this page are design targets only and have not been validated through prototype testing. The NitrogenMeter™ has not been manufactured, tested, or sold. Concept renderings and display mockups are illustrative representations of the intended design and do not represent a finished product. Patent Pending — App. No. 64/090,362 filed June 14, 2026. A provisional patent application does not grant the rights of an issued patent.