- Parameters
- COD, TOC, UV275, TDS, conductivity and temperature; LS311 adds salinity, hardness and specific gravity
- Measuring range
- COD 0 to 100 mg/L; TOC 0 to 100 mg/L; UV275 0 to 1.0 au/cm; TDS 0 to 2000 ppm; conductivity 0 to 4000 µS/cm; temperature 0 to 50 °C
- Resolution
- COD and TOC 0.01 mg/L; UV275 0.001 au/cm; TDS 1 ppm; conductivity 1 µS/cm; temperature 0.1 °C
- Accuracy
- COD and TOC ±0.5 mg/L below 5 mg/L and ±10% H above; TDS and conductivity ±3% FS; temperature ±1 °C
- Display
- 1.14 inch TFT, 240 × 135, with a backlight in four colours keyed to the score band
- Keys
- Power and measure, two keys in total
- Probe
- Immersion sensor with a minimum water line marked on the body; IP67
- Power
- Two AAA alkaline cells
- Body
- 157 × 37 × 14 mm, about 68 g
- Environment
- 5 to 50 °C at up to 85% RH without condensation; storage −10 to 60 °C
Water quality is usually judged with a kit: a strip, a reagent, a meter for each parameter and a note of the results. The tester in this range replaces the kit with one immersion, and replaces the interpretation with a score.
Product overview
A pen with a sensor at the lower end and a small colour display on the front. Two keys, one of which measures.
Six quantities come out of a single immersion: the organic indicators, the ionic indicators and the temperature. The display shows them together and adds a score, with the backlight changing colour to match the band the score falls in.
The body is 68 g and fits a pocket. The probe is capped when not in use and has a marked minimum immersion line, so the same depth is used each time.
How the tester reads the water
The probe measures absorbance in the ultraviolet at 275 nm, which is where dissolved organic matter absorbs, and it measures the conductivity of the sample between electrodes. Temperature is measured at the same point and is used to compensate the ionic reading, because conductivity rises with temperature and a reading without compensation is a reading of the water plus the weather.
The organic figures are presented as COD, TOC and UV275. All three describe the same underlying question - how much oxidisable or ultraviolet-absorbing material is in the water - at different scales, which is why they move together and why a single one of them is a poor basis for a decision.
The score is what turns the readings into an answer. It is calculated across the parameters rather than from any one of them, and the colour of the backlight follows the band. That is deliberate: a water with a high mineral content reads badly on TDS alone but can be perfectly good to drink, and a water with low TDS can still carry an organic load.
How to select the right model
The base model covers the six parameters that describe drinking water: the organic load, the dissolved solids, the conductivity and the temperature.
The higher model adds salinity, hardness and specific gravity. Those are descriptive rather than diagnostic: they tell you what kind of water it is - how hard, how salty, how dense - rather than whether it is fit to drink.
The choice therefore follows the question being asked. A quick check of a tap or a filter output needs the six. Describing a mineral water, checking a softener, or comparing sources needs the additional three.
Neither model logs. If results have to be kept, they are written down or photographed; there is no memory and no export in the material.
Measurement limitations and selection considerations
The sample type is drinking water, not wastewater. The ranges are built around clean water, and a sample with a high organic load will sit at the top of the range rather than produce a useful figure. Effluent, process water and heavily polluted surface water need a different instrument.
Immersion depth and probe cleanliness decide the reading as much as the electronics. The minimum water line exists to make the depth repeatable, and a probe with a film on it - from a previous sample, from hard water, or from handling - reads the film as well as the water. Rinsing with the sample before measuring is part of the method, not an optional step.
The score is a summary and should be treated as one. It is a good way to sort many samples quickly; it is not a substitute for the individual readings when a result has to be defended, and it is not a compliance measurement against a drinking water standard. The reference standard behind the scoring is a benchmark, not a certificate.
Temperature compensation corrects the ionic reading, not the organic one. A cold sample and a warm sample of the same water will agree on conductivity after compensation but can differ slightly on the optical figures, so comparisons should be made at similar temperatures.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
