Hach 2100Q portable turbidimeter for field-based turbidity measurement in drinking water, wastewater, cooling tower, boiler and industrial process water. Auto-ranging 0-1000 NTU (or 0-1000 FNU on the ISO variant), accuracy plus/minus 2 percent of reading + stray light, resolution 0.01 NTU low range (0-9.99), 0.1 NTU mid range (10-99.9), and 1 NTU high range (100-1000). Repeatability plus/minus 1 percent of reading or 0.01 NTU whichever is greater. Signal Averaging selectable on/off. Two device variants — pick by regulator: 2100Q01 (Hach standard USEPA 180.1 compliance, halogen-filled tungsten filament lamp) — for US drinking-water and USEPA reporting; 2100Q IS 01 (ISO 7027 compliance, 860 nm LED light source) — for European DWD and international ISO-referenced reporting. Also compatible with Hach Method 10258 and Standard Methods 2130 B. Both variants use ratio nephelometric measurement (90-degree scattered light ratioed to 180-degree transmitted light) with a two-detector optical system that compensates for sample colour and turbidity colour. Verified Hach factory kit part numbers: 2100Q01 (EPA, base configuration), 2100Q01USB (EPA + USB and Power Module for AC and data), 2100QIS01 (ISO 7027, base configuration), 2100QIS01USB (ISO + USB and Power Module). Every kit ships with: meter, 6 sample cells with screw caps, StablCal sealed-vial calibration set (10 / 20 / 100 / 800 NTU), silicone oil, oiling cloth, 4 x AA alkaline batteries, printed manual, and hard carrying case. 500-reading data log with timestamp, operator ID and sample identifier. Data export via the optional USB and Power Module (XML) — no native RS-232 or IR on the meter itself. Power: 4 x AA alkaline (typical ~300 readings) or AC via the USB and Power Module. Sample volume 15 mL (0.5 oz). Dimensions 77 x 107 x 229 mm; weight ~0.5 kg without batteries. IP67 rated with battery cover installed. Verified consumable and calibration part numbers (Hach official): sample cells — 2434706 (Portable Turbidimeter Sample Cells 6-pack, 25 mm round glass with screw cap); silicone oil for optical matching — 126936 (15 mL bottle); StablCal Sealed Vials calibration kit — 2971205 (one each 20, 100, 800 NTU calibration standards + 10 NTU verification, USEPA-accepted for the 2100Q's tungsten-lamp EPA-compliant work); StablCal 100 mL bottles — 2971210 (10, 20, 100, 800 NTU); StablCal 500 mL bottles — 2971200 (10, 20, 100, 800 NTU). StablCal is Hach's stabilised primary formazin standard; it supersedes the older Gelex secondary standards used with the 2100P. Recommended calibration frequency: every 3 months or when verification fails. Reagents: NONE. The 2100Q measures scattered light from suspended particles directly (nephelometric); it is NOT a colorimeter and consumes no reagent chemistries. Contrast with Hach DR900 / DR1900 / DR3900 colorimeter and spectrophotometer lines which DO require reagents. Applications: municipal drinking-water compliance monitoring (USEPA and EU Drinking Water Directive reporting), source water and filter effluent, cooling-tower and boiler makeup/blowdown, wastewater final effluent turbidity, aquaculture water quality, and in marine service as a field check instrument for ballast-water discharge clarity verification alongside BWMS (Techcross ECS, Alfa Laval PureBallast, JFE, Ecochlor, Optimarin, Erma First). Note: the 2100Q is used as an operator check instrument; regulated ballast-water discharge sampling per IMO G8/BWMS Code and USCG-approved protocols is defined by grab or composite sampling with lab analysis, not by in-line portable turbidimetry. Predecessor: Hach 2100P Portable Turbidimeter (now obsolete on hach.com); 2100Q inherits the field-portable role. The Hach TU5200 (laboratory benchtop) and TU5300 sc (online process, 360x90-degree laser optics with sub-1 NTU sensitivity) are current-generation lab/online instruments, NOT portable-2100Q replacements — different form factor and use case. See our companion Techcross ECS Electro-Cleen BWMS spare parts reference document for adjacent BWMS-check-instrument context. cBallast supplies the 2100Q family, StablCal calibration standards (2971205 / 2971210 / 2971200), sample cell 6-packs (2434706), silicone oil (126936), replacement USB and Power Modules, and carrying-case spares ex-EU stock. Request a quote by variant part number (2100Q01 vs 2100QIS01 — specify USEPA vs ISO 7027 regulatory need) and calibration-standard format (sealed vials for fast field cal vs bulk bottles for lab or fleet).