Hach 2100Q / 2100Qis Review & Complete Reference (2026): Portable Turbidimeter
Source: Hach User Manual DOC022.53.80041 Edition 6 (August 2021) • Hach Company, Loveland, Colorado • Danaher subsidiary
EPA Method 180.1 (2100Q) • ISO 7027 (2100Qis) • 0–1000 NTU/FNU • IP67 • StablCal RapidCal • 500-record data log • USB XML export
0–1000 FNU (2100Qis)
2100Q vs 2100Qis — The Only Decision That Matters
The two models are operationally identical. The sole differentiator is the light source and the regulatory standard each satisfies. Choose based entirely on which regulatory framework applies to your monitoring program.
Units: NTU
Standard: EPA Method 180.1
Lamp: User-replaceable (Part 4653900)
Use when: US drinking water compliance, NPDES discharge permits, US environmental monitoring programs
Units: FNU
Standard: ISO 7027
Lamp: NOT user-replaceable (Hach service required)
Use when: EU water quality directives, international regulatory frameworks, non-US programs
Calibration System — Complete Reference
Accurate turbidity measurement is entirely dependent on proper calibration. The 2100Q/2100Qis supports seven calibration curve types and provides a fully on-screen guided workflow. Hach recommends full calibration every three months and verification once per week.
| Calibration Type | Standards Required | Range | Best For |
|---|---|---|---|
| StablCal (Full-Range) | 20, 100, 800 NTU StablCal ampules | 0–1000 NTU | Standard calibration for all applications |
| StablCal RapidCal | 20 NTU StablCal ampule only | 0–40 NTU only | Routine drinking water compliance — fastest workflow |
| Formazin | Primary formazin standards | Full range | Primary standard calibration when regulatory traceability to formazin is required |
| Degrees | Secondary degree standards | Full range | Comparison to Degrees Jackson Turbidity (historical) |
| SDVB | SDVB bead standards | Full range | Specific applications requiring SDVB traceability |
| Custom 1 / Custom 2 | User-defined standards | User-defined | Specialized applications requiring non-standard curves |
Full-Range StablCal Calibration (3-Point, 0–1000 NTU)
Perform upon receipt and every three months thereafter. Uses 20, 100, and 800 NTU StablCal ampules.
Push CALIBRATION key to enter Calibration mode
The display guides through the sequence automatically.
Gently invert the 20 NTU StablCal standard — do NOT shake
Inversion distributes the suspension evenly. Shaking creates air bubbles that cause erroneously high readings. Insert with orientation mark aligned. Close the lid.
Push Read — display shows 'Stabilizing' then reading result
Wait for the reading to complete before proceeding.
Repeat with 100 NTU standard — gently invert, insert aligned, close lid, Read
Push Done after this step to complete a 2-point calibration if full range is not needed.
Repeat with 800 NTU standard — gently invert, insert aligned, close lid, Read
Push Done → review calibration summary → push Store to save
Calibration is logged with date and time. Instrument automatically enters Verify Cal mode after storing — proceed with verification.
StablCal RapidCal — Single-Standard Fast Calibration (0–40 NTU)
Push CALIBRATION key → use UP/DOWN to access Cal Options → select Cal.Curve
Select 'StablCal RapidCal' from the list → push OK
Gently invert the 20 NTU StablCal standard — insert aligned — close lid — push Read
One standard is all that is required for RapidCal.
Push Done → review calibration details → push Store
Calibration is saved and the instrument is limited to the 0–40 NTU range until recalibrated with full-range StablCal.
Calibration Verification (Weekly)
Verification confirms the instrument continues to produce accurate readings since the last calibration. Default standard: 10.0 NTU ±10%. Perform weekly and immediately after any full calibration.
Push LEFT key (labeled 'Verify Cal') from the measurement screen
Apply silicone oil to sample cell — gently invert the 10.0 NTU verification standard — insert aligned — close lid
Push Read — display shows result and tolerance range (±10% default)
If verification fails, repeat the full calibration procedure. A verification reminder can be configured to alert at intervals of 30 min, 2 h, 4 h, 8 h, or 24 h.
Standard Measurement Procedure
Measurement Best Practices
- Place on level, stationary surface — never hold while reading
- Always close lid during measurement
- Avoid direct sunlight — ambient light causes high readings
- Allow cold instrument to equilibrate before use
- Always cap cell before inserting
- Handle cell by the top only — fingerprints cause high readings
- Wipe exterior with lint-free cloth before insertion
- Apply silicone oil — required, not optional
- Store filled with DI water, capped — never air-dry
Collect representative sample — fill cell to 15 mL line — handle by top — cap
Measure immediately after collection — settling and temperature change alter turbidity.
Wipe cell exterior with soft, lint-free cloth
Remove water spots, fingerprints, and dust.
Apply silicone oil — thin, uniform film over entire exterior surface
Use ONLY the provided silicone oil. Other oils have different refractive indices and introduce measurement errors. See the silicone oil section below for full procedure.
Power on — place on flat, level surface
Gently invert sample cell to homogenize — insert aligned with orientation mark — close lid
Push Read — display shows 'Stabilizing' then turbidity value in NTU (or FNU)
Result is shown and stored automatically in the data log.
Three Reading Modes
| Mode | How It Works | Best For | Display Indicator |
|---|---|---|---|
| Normal | Measures continuously and displays a running average. Stops and locks when the reading is stable. | Stable, clear samples; general use | No icon (default) |
| Signal Average | Averages a user-defined number of readings before displaying a result. Reduces variability on inconsistent samples. | Samples with slight variability; noisy optical environment | X-bar icon (¯X) |
| Rapidly Settling Turbidity (RST) | Measures the turbidity of the sample before particles settle. Extrapolates the t=0 turbidity from the settling curve. | Samples with particles that settle quickly (iron, silt, floc); most effective above 20 NTU | Target icon |
| RST requires sample to be homogeneous at the start — thoroughly invert immediately before inserting. If settling too slow for RST to detect, display shows 'RST: Average value!' — switch to Normal or Signal Average mode. | |||
Silicone Oil Application — Full Procedure
Silicone oil application is required for every measurement — not optional. The oil is formulated to match the refractive index of the borosilicate glass cells, filling microscopic surface defects that would otherwise scatter light and cause systematically elevated readings.
Clean the cell inside and out with laboratory glass cleaning detergent — rinse multiple times with distilled or deionized water
Apply a small bead of silicone oil from the top to the bottom of the external surface
Use the provided oiling cloth to spread oil uniformly over the entire external surface
Wipe off excess — only a very thin coat should remain. The cell should appear almost dry with little or no visible oil.
Store the oiling cloth in a plastic storage bag after use
Contamination of the oiling cloth with other substances defeats its purpose and contaminates future cells.
Cell Indexing for Low-Turbidity Precision
For very low turbidity measurements, the rotation position of the cell within the instrument affects the reading due to minute optical variations in the cell glass. Cell indexing identifies the position that yields the lowest (most accurate) reading and permanently marks it so the cell is always inserted at the optimal orientation.
Fill clean cell to 15 mL with high-quality water (<0.5 NTU) — cap immediately — allow to degas 5 minutes
Apply silicone oil — power on — place on flat surface
Insert cell aligned with diamond mark — close lid — navigate to Reading Options → 'Indexing Sample Cell' → push Read
Note the displayed reading and cell position.
Remove cell — rotate approximately 1/8 turn — reinsert aligned — push Read
Record reading and position. Repeat through 8 positions (one full rotation).
Place a permanent orientation mark on the cell at the position yielding the lowest reading
Always insert this cell at this orientation for all future measurements. This single step can reduce low-level measurement variability by 0.05–0.1 NTU.
Data Management
| Log Type | Capacity | Contents |
|---|---|---|
| Reading Log | 500 records | Turbidity value, date/time, operator ID, sample ID, reading mode, calibration status |
| Calibration Log | 25 records | Calibration type, standard values used, date/time, pass/fail status |
| Verification Log | 250 records | Verification standard value, result, tolerance, pass/fail, date/time |
| All data stored in non-volatile memory. Data survives battery changes and power-off cycles. USB export generates XML files compatible with Microsoft Excel and LIMS platforms — no proprietary software required. | ||
Maintenance Reference
Battery Replacement
Remove battery cover from the rear. Remove old batteries. Install 4 AA alkaline or 4 AA NiMH batteries, ensuring correct polarity per markings inside the compartment. Replace and secure battery cover. Note: the battery compartment is not waterproof — the IP67 rating applies only to the main body with the sample compartment lid closed.
Lamp Replacement (2100Q Only)
The tungsten filament lamp of the 2100Q (Hach part number: 4653900) is user-replaceable. Steps: (1) Power off and allow lamp to cool completely. (2) Access lamp compartment (rear). (3) Remove lamp cover (part LZV822). (4) Remove defective lamp assembly. (5) Install new lamp assembly, ensuring correct seating. (6) Replace cover and secure. (7) Power on and verify with a known standard.
Replacement Parts & Accessories Reference
| Part Number | Description |
|---|---|
| 4653900 | Replacement lamp for 2100Q (tungsten filament) — user-replaceable |
| LZV822 | Lamp cover assembly (includes screws) |
| 26084-00 | Sample cells, 10 mL, matched set of 4 (with lids) |
| 2271506 | StablCal Stabilized Standards Kit (0.1, 20, 100, 800 NTU) |
| 2630901 | Silicone oil, 4 oz |
| 2630800 | Oiling cloth (replacement) |
| 2657801 | USB module (data transfer without AC power) |
| 2657701 | USB/power module (data transfer + AC power) |
| 4924801 | Instrument carrying case |
| 4924901 | Instrument with USB module (2100Q01USB kit) |
Troubleshooting Reference
| Display/Symptom | Probable Cause | Corrective Action |
|---|---|---|
| Overrange! | Sample turbidity exceeds calibration range. If RapidCal was used: sample >40 NTU. | Recalibrate with full-range StablCal (0–1000 NTU) OR dilute sample with <0.5 NTU water and correct for dilution factor. |
| Calibration ? | Calibration has not been performed or calibration verification failed. | Perform full StablCal calibration. Verify with 10.0 NTU standard. If verification fails, repeat calibration. |
| RST: Average value! | Sample settles too slowly for RST mode to detect a trend. | Switch to Normal or Signal Average mode. RST is most effective for samples >20 NTU with rapidly-settling particles. |
| Readings systematically high | Silicone oil not applied; dirty or scratched sample cell; fingerprints on measurement area; ambient light entering compartment | Apply silicone oil per procedure. Clean cell with detergent and DI water. Handle cell by top only. Avoid direct sunlight during measurement. |
| Readings variable between identical samples | Cell not inserted at consistent orientation; silicone oil not applied uniformly; sample not fully homogenized before insertion | Perform cell indexing procedure. Reapply silicone oil uniformly. Invert sample immediately before inserting to resuspend settled particles. |
| Instrument locked (password protected) | Security Options enabled and password forgotten. | Contact Hach technical support. There is no user-accessible password reset procedure. |
| Battery compartment wet | Field exposure; condensation | Remove batteries immediately. Dry compartment and batteries. Check contacts for corrosion. Do not reinstall until fully dry and contacts clean. |
| Data transfer not working | USB module not properly installed; instrument not connected to AC power during transfer | Verify USB/power module is fully seated in module slot. AC power connection is required for data transfer. Confirm USB connection to computer or storage device. |
Related Instrument References
- Hach DR900 Multiparameter Colorimeter — water quality colorimetric analysis
- Hach DR1900 Portable Spectrophotometer — lab-grade field spectrophotometry
- Hach DR300 Pocket Colorimeter — single-parameter colorimetric testing
- YSI Pro20 Dissolved Oxygen Meter — complementary field parameter
- Apera PC60 Multiparameter Meter — pH, EC, TDS, salinity
- Colorimeter vs Spectrophotometer — Buyer’s Guide