Conductivity Meters & Accessories: what Claude and GPT would buy
Two AI models chose on their own, with no web access. Nobody tested these products: this is what each one says, and how to check it.
Claude and GPT choose the same brand, Hanna Instruments, but not the same product
In Industrial & Scientific, Claude and GPT choose the same brand in 52 of 107 categories.
Claude Opus 5.5 · October 28, 2026
Hanna Instruments DiST (line)
Hanna's DiST pocket EC/TDS testers are accurate, temperature-compensated and user-calibratable, and they cover the most common water, hydroponic and process checks without a bench setup.
Not for: Labs needing GLP-logged, traceable readings or ultrapure-water measurements below a few µS/cm.
GPT 6.1 Sol · November 10, 2026
Hanna Instruments Combo HI98129
Measures conductivity, TDS, pH, and temperature in one waterproof handheld, with automatic temperature compensation and a replaceable pH electrode.
Not for: Samples exceeding its 3,999 µS/cm conductivity range or continuous process monitoring.
Which one fits you
hydroponic nutrient dosing
Bluelab Truncheon (line)
A rugged, fixed-cell nutrient meter that needs no calibration and reads directly in grower units.
Not for: Anyone needing a µS/cm readout across wide ranges or lab-grade accuracy.
benchtop lab with data logging
Mettler Toledo SevenCompact (line)
A benchtop line with interchangeable conductivity cells, multi-point calibration and GLP-style records.
Not for: Field users and anyone needing only occasional spot checks.
Check before you buy
Where to find Hanna Instruments DiST
- Gemplers
- Zoro
- Thermal Scientific
Shops seen in search results on November 6, 2026. A shop missing here may sell it too. Nothing was checked by a person.
Brands that matter
- Hanna Instruments: Broad range, from pocket testers to benchtops, with easily sourced standards.
- Mettler Toledo: Lab benchtops with strong data-integrity features.
- Thermo Scientific Orion: Lab-standard benchtops and conductivity cells.
- Bluelab: Hydroponics-focused, rugged and simple.
- Apera Instruments: Value-oriented pens and benchtops.
- Oakton: Established lab and field testers.
What to avoid
- Unbranded TDS pens with no calibration adjustment
- Using one meter and cell for both ultrapure water and brines
- Contaminated or expired calibration standards
Questions
Is TDS the same as conductivity?
No. TDS is estimated from conductivity using a conversion factor, so it is only as good as that factor for your water.