GREENWORLD SECTOR-7 // METRICS // VC-MET-309
ALL SYSTEMS NOMINAL · —
METRICS · OPERATIONS & RESOURCE

Nutrient Dosing Rate

VC-MET-309 — the volumetric injection rate of concentrated nutrient stock into the hydro-loop in millilitres per minute, a two-sided metric guarding against both under- and over-dosing.

Metric ID VC-MET-309 Category Operations & Resource Unit mL·min⁻¹ Type Direct Source PhytoSense Mesh Sampling 1 min Owner Metrology & Telemetry Standards Rev C · Effective 2089-06-01
Current 19 mL·min⁻¹ Nominal 12–28 mL·min⁻¹ 1-min cadence Dosing-pump flow via PhytoSense Mesh

Definition

Nutrient Dosing Rate (NDR) is the instantaneous volumetric rate, in millilitres per minute, at which concentrated nutrient stock is injected into the hydro-loop by the dosing pumps to hold the loop's target electrical conductivity. It is read directly from the dosing-pump flow sensors. NDR is a two-sided control variable: too low and the loop drifts nutrient-deficient, starving the collection; too high and conductivity overshoots, risking osmotic stress and wasting stock concentrate.

Why it matters

Nutrient delivery sits directly upstream of plant health: a dosing fault propagates to every bench on the loop within an irrigation cycle and shows up as conductivity drift long before vitality (VC-MET-001) reacts. Because the dosing pumps are actuated by a closed conductivity loop, an abnormal NDR is often the first sign the controller is fighting a sensor fault, a clogged injector, or a depleted stock tank. NDR is monitored on the Operations Dashboard and interlocked to halt dosing on runaway.

Formula

NDR is a directly measured pump flow; the model covers the control context and interlocks:

NDR = Q_dose      [mL·min⁻¹, from dosing-pump flow sensor]

Control context (the loop that commands NDR):
  NDR_cmd = PID( EC_target − EC_loop )
  EC_loop  measured downstream; EC_target per cultivar recipe

Plausibility cross-check (two-sided):
  expected_EC_slope = f(NDR, loop_volume, stock_strength)
  if measured EC does not move with commanded NDR  →
     flag DOSING_DECOUPLED (clog, empty tank, or EC sensor fault)

Interlocks:
  NDR > 48 mL·min⁻¹ sustained 60 s  →  halt dose, lock pump
  NDR < 4 mL·min⁻¹ with EC below band  →  flag UNDERFEED,
     escalate before deficiency reaches the canopy.

Flow-sensor accuracy ± 0.3 mL·min⁻¹; zeroed at each stock change.

Inputs

ChannelRoleCadenceReferenceSource
Dosing-pump flowDirect NDR measurement1 minmL·min⁻¹, ± 0.3PhytoSense Mesh
Loop EC sensorControl feedback & decoupling check1 minTarget EC bandPhytoSense Mesh
Stock tank levelEmpty-tank / underfeed context5 min% fullPhytoSense Mesh
Cultivar recipeEC_target set-pointPer recipeRecipe tableCHLORA

Units & Scale

NDR is reported in mL·min⁻¹ to whole-unit precision per dosing channel. It is a point measurement at each injector, not an aggregate; multi-part recipes (A/B/acid) report a channel each. The published trend uses a 3-sample median for readability while thresholds act on the unsmoothed flow. A DOSING_DECOUPLED flag degrades confidence when commanded flow fails to move loop conductivity as expected, indicating a clog, empty tank, or EC sensor fault rather than a true dosing change.

Sampling & Source

Thresholds

Nominal · 12–28 mL·min⁻¹

OK

Conductivity held on recipe. No action.

Warning · < 8 / > 36 mL·min⁻¹

WARN

Low: underfeed risk. High: overshoot; verify EC sensor.

Critical · < 4 / > 48 mL·min⁻¹

CRIT

Low: stock empty / clog. High: runaway; halt dosing.

Two-sided dosing interlock. NDR alarms on both edges. On the high side, > 48 mL·min⁻¹ sustained for 60 s halts the dose and locks the pump to prevent conductivity runaway and osmotic shock; on the low side, < 4 mL·min⁻¹ with EC below band latches an UNDERFEED and escalates before deficiency reaches the canopy. Both criticals require manual reset after the EC sensor and stock tank are verified. WARN hysteresis: clears only after NDR returns inside 10–30 mL·min⁻¹ and EC tracks for 5 minutes.

Recent Trend

Dosing-channel flow in mL·min⁻¹, last 14 one-minute samples:

NDR · 14-sample trend, mL·min⁻¹ (current 19)

Interpretation Guidance

NDR BandReadingLikely DriverAction
< 4 mL·min⁻¹CRIT lowEmpty stock or clogged injectorHalt deficiency; replace stock / clear clog.
4–7.9 mL·min⁻¹WARN lowUnderfeed or low demandVerify EC sensor and tank level.
12–28 mL·min⁻¹NominalNormal EC trackingNone; normal operating band.
36.1–48 mL·min⁻¹WARN highEC undershoot or sensor reading lowValidate EC sensor; check for dilution event.
> 48 mL·min⁻¹CRIT highController runaway or sensor faultPump locks; invoke dosing-fault SOP.
VC-MET-306

Hydro-Loop Pressure

Dosing injects into the loop.

 VC-MET-307

Water Reclamation Efficiency

Returned water carries residual EC.

 VC-MET-310

Substrate Stock Coverage

Nutrient stock is a consumable.

 VC-MET-303

Alarm Acknowledgement Latency

Dosing CRIT raises alarms.

 VC-MET-001

Canopy Vitality Index

Nutrient drift depresses vitality.

 VC-MET-106

Substrate Moisture

Co-delivered with nutrient solution.

Related SOPs