TLF Serial Dilution — Tryptophan

Overview

A serial-dilution characterization of the Lume’s tryptophan-like fluorescence (TLF) channel (mon2_val, the SiPM signal). A tryptophan stock solution is stepped down through a serial dilution while all 14 sensors read the same bath, so each sensor sees an identical, known concentration at each step. The goal is a per-sensor TLF → concentration response and a check of linearity, sensor-to-sensor spread, and limit of detection.

TLF is the primary E. coli–bearing signal in the field model, so a clean concentration–response curve on a pure tryptophan standard is the fluorophore analog of the ToF → NTU turbidity calibration. This page reads the sensors live during the test; enter the dilution steps below to build the calibration curve as data comes in.

Live TLF Readings

Raw mon2_val per sensor over the test window, pulled from the sensor API (combo: 'best' — the calibrated combo per unit). These 14 units auto-range, so the operating combo (LED power) can differ between units; hover a point to see its combo. Absolute mon2 is only comparable within a sensor across steps, not between sensors at different LED powers.

Normalized TLF (re-zeroed to this test’s 0-concentration step)

The same signal, normalized to this test’s blank: each sensor’s zero is its own median reading during the 0-concentration step, subtracted from its trace. Every sensor therefore sits at ~0 across the 0-conc step, and a rise is that sensor’s tryptophan response relative to the test blank — not the lab clean-water baseline. This removes each unit’s offset so the 14 dilution curves are directly comparable. Mark the blank by adding a step with concentration 0; sensors with no reading in that window are omitted.

Temperature

Water/sensor temperature per unit over the test window (from the diagnostics channel). Temperature quenches TLF, so it’s the covariate to watch when interpreting the dilution response — a drift here can move mon2 independently of tryptophan.

Calibration — Normalized TLF vs Concentration

Each sensor’s median normalized TLF (median mon2 over a step − its 0-conc blank) plotted against the known concentration, origin at (0,0). Define the dilution steps and concentrations in the Dilution Steps card below to populate this.

Dilution Steps & Calibration

Add each dilution step below with its start/end time and known tryptophan concentration. Each point on the curve is a sensor’s median mon2_val over that step’s time window against the known concentration; steps are also shaded on the live chart above. Leave concentration blank to just mark a step on the timeline. Steps are saved to the server for this test, so they persist across reloads and are shared with anyone viewing the page. Export JSON / Import JSON are available for backup.

Sensors Under Test

The same 14 units running the acceptance / dilution firmware (v0.1.18, 20-min reporting): 8 acceptance-test units and the 6 units pulled from the Boulder Creek field deployment.