Frequently asked questions
37 answers across product, industry and general topics. Use the section links below to jump.
General questions
What is an industrial online density meter? How does it differ from a lab density meter?
An industrial online density meter mounts directly on a process pipe or vessel and continuously outputs density (or concentration) in real time. Three key differences vs lab pycnometers and benchtop oscillating-tube units: (1) continuous measurement, no sampling required; (2) outputs 4-20mA / Modbus signals that integrate directly with DCS / PLC; (3) ingress protection, hazardous-area certification and wetted-parts materials designed for industrial sites. Pisonics offers online density meters across ultrasonic, tuning fork, differential pressure, Coriolis, optical, microwave, and radiometric principles — covering heavy slurries to clean liquids.
For slurry density measurement: tuning fork or Coriolis?
Short answer: choose tuning fork (PS7400) for high-solids slurries with insertion-style installation; choose Coriolis (PS7210 / PS7220) for in-line pipeline measurement where abrasion is manageable.
- Tuning fork handles scaling and entrained gas well, typically ranges 0.5–3.0 g/cm³, with simple mechanics and low maintenance. Severe abrasion requires a wear-resistant fork tip.
- Coriolis offers higher accuracy (±0.0005 g/cm³) and simultaneous mass-flow measurement. But it's more expensive, has pipe-size constraints, and is sensitive to bubbles.
For mining ore-dressing overflow / underflow with 30–60% solids, tuning fork dominates. For downstream chemical reactors or FGD wastewater (cleaner streams), Coriolis is often the better fit.
How do I pick the right density meter principle for my application?
Four dimensions: (1) medium — solids fraction, entrained gas, scaling tendency, corrosivity; (2) installation constraints — whether tapping/hot work is allowed, straight run available, pipe size; (3) accuracy — custody transfer needs ±0.0005 g/cm³ (Coriolis); process monitoring tolerates ±0.005 g/cm³; (4) compliance — whether a radioactive source is acceptable. Common matches: gassy slurries → PS7000 acoustic impedance; no tapping → PS7010 clamp-on; high-accuracy clean liquids → PS7200 Coriolis; heavy scaling → PS7400 tuning fork; large-bore main → PS7300 DP; water-bearing suspensions → PS7600 microwave; ultra-precise optical → PS7100 spectroscopy / PS7110 refractometer.
Accuracy vs repeatability — what's the difference, and which matters more?
Accuracy is deviation from the true value — ±0.002 g/cm³ means the reading may run 0.002 above or below actual density. Repeatability is the spread between successive measurements on identical material — ±0.0005 g/cm³ means the trace won't wander beyond that band. For selection: custody transfer and quantitative batching demand accuracy; trend monitoring, process control, and alarm thresholds depend on repeatability. Most sites need both, but repeatability has the bigger day-to-day impact — a noisy reading floods the DCS with false alarms even when long-term accuracy is fine.
Which non-nuclear alternatives exist to replace gamma (γ-ray) density meters?
Pisonics offers four non-nuclear principles: (1) PS7000 acoustic impedance — bubbly mining slurries and high-abrasion media; (2) PS7010 acoustic attenuation — clamp-on for no-tapping scenarios; (3) PS7400 tuning fork — scaling-prone chemical slurries; (4) PS7300 differential pressure — large-bore mains (DN200+). If radiometric principle is still required (heavy-media coal washing), PS7500 Na22 uses an exempt-activity source (< 1000 KBq) — no radiation license or transport permit needed.
Do Pisonics meters come in explosion-proof variants? Which Ex ratings are supported?
Most Pisonics meters offer Ex variants: ultrasonic series (PS7000 / PS7010 / PS7020) — ExdⅡCT6Gb; tuning fork PS7400 — Ex d ⅡC T6 Gb; Coriolis PS7200 — Ex d ⅡB T6 Gb; differential pressure PS7300 — intrinsic safety ExiaIICT6 and flameproof ExdIIBT4; spectroscopy PS7100 / refractometer PS7110 — Ex db ib IIC T6 Gb; microwave PS7600 — custom Ex available. All Ex variants are CE certified. When ordering, specify your hazardous zone classification (Zone 0 / 1 / 2) and required temperature class.
What's the lead time? Can the meter be customized?
Standard models ship in 4~6 weeks. Customized models (special wetted materials like 2205 duplex stainless / Hastelloy / titanium, non-standard ranges, special liners, Ex variants, sanitary connections) take 6~10 weeks. Bulk and urgent orders can be expedited. All product lines support process customization: probe length, process connection (flanges ANSI / DIN / JIS, sanitary tri-clamp, threaded), cable length, display language, communication protocol. Before ordering, our engineers confirm parameters and issue a written sizing proposal.
How often do meters need calibration? What's the procedure?
Under typical conditions, every 12~18 months for zero / span verification. Application-dependent: clean stable media (finished products, syrups) can extend to 24 months; abrasive solids or high temperature call for 6~12 months. Methods: (1) manual sample lab analysis vs meter reading, adjust offsets; (2) on-site calibration solution method (known-concentration salt solutions); (3) remote support via RS485 / 4G to the Pisonics remote diagnostic system. Factory-traceable calibration with our temperature-controlled lab equipment is available for custody-transfer customers.
Are Pisonics meters available for export? What international certifications are held?
Yes — Pisonics meters have shipped to Southeast Asia (Vietnam, Indonesia, Malaysia), the Middle East (Saudi Arabia, UAE), Africa (South Africa, Zambia), South America (Chile, Peru), and CIS countries (Russia, Kazakhstan). Major certifications: CE marking (EU), ATEX / IECEx hazardous-area approval (selected models), RoHS compliance. We provide EN 10204 3.1 material certificates, English user manuals, installation/commissioning video tutorials, and remote technical support (engineers fluent in Vietnamese, Spanish, Russian and other languages).
PS7210 (bent tube) vs PS7220 (straight tube) — which Coriolis to choose?
Both PS7000 and PS7010 are ultrasonic — what's the actual difference?
Both use ultrasound, but principles and applications differ completely. PS7000 acoustic impedance: single transceiver, measures echo from interface reflection. Pros: strong bubble immunity (Chirp wideband algorithm), broad medium adaptability (two-phase slurries); install: flanged insertion, tapping required. PS7010 acoustic attenuation: dual probe (transmitter + receiver opposite each other), measures energy attenuation after transmission. Pros: clamp-on no-tap option (some conditions), simple reliable principle, good accuracy on clean slurries; cons: bubble-sensitive, clamp-on demands stable wall thickness. Rule of thumb: gassy → PS7000; no tapping → PS7010; standard cases — either works.
By product
Questions tagged to a specific Pisonics SKU.
Is the PS7000 ultrasonic density meter a radiometric device? Does it need a radiation license?
The PS7000 is an acoustic-impedance ultrasonic density meter with no radioactive source whatsoever. No radiation license is required. It uses only piezoelectric transducers to send and receive ultrasonic signals — the same physical principle as medical and NDT ultrasound.
If you're currently using a Cs-137 / Co-60 source-based meter and want to remove the regulatory burden, PS7000 is a drop-in alternative. We also offer the PS7500 gamma meter, which uses an exempt-activity Na-22 source (< 1000 KBq) — also requires no radiation license.
Can PS7000 really measure stably in bubbly mining slurries?
Yes. PS7000 uses a Chirp (linear FM sweep) acoustic-impedance algorithm — wideband ultrasonic pulses, then spectrum-based echo analysis identifies and rejects multi-path interference from bubbles. This is the key difference from traditional single-frequency reflection ultrasonic meters: those are bubble-sensitive; the PS7000 Chirp algorithm is essentially bubble-immune. At an Inner Mongolia thermal plant FGD gypsum line (heavy bubbles from forced oxidation), PS7000 replaced the original tuning-fork meter and ran multi-year stable.
What installation requirements does the PS7000 have?
PS7000 mounts via flanged insertion. Requirements: (1) straight run ≥ 5D upstream + 2D downstream; (2) installation point must run full (no two-phase stratification); (3) pipe range DN50~DN1000 (larger custom available); (4) flange standards: ANSI / DIN / JIS; (5) for high abrasion, 316L + special ceramic or 2205 duplex; (6) PTFE liners for corrosion. If tapping is forbidden, use PS7010 clamp-on instead.
Is the PS7010 clamp-on really tap-free? Does it work on all pipes?
What advantages does PS7020 (sound velocity) have over an optical refractometer?
Can PS7100 spectroscopy measure multiple components simultaneously?
Yes. PS7100 uses UV-Vis-NIR absorption spectroscopy (200~1700 nm) with an MLR (multi-linear regression) algorithm — a single measurement outputs the concentration of multiple components in parallel. Typical applications: chlor-alkali sodium hypochlorite — simultaneous available chlorine + free NaOH (R² > 0.99); mixed acids (HCl + H₂SO₄); semiconductor wet etching (HF + HNO₃); biopharma fermentation Brix + alcohol. Multi-component needs upfront modeling — Pisonics builds a custom MLR model from your medium sample in our lab (2~4 week turnaround).
How durable is the PS7110 sapphire prism? Does it need cleaning?
How do I choose between PS7300's three mounting styles (A/B/C)?
View product · Pipeline Differential Pressure Density Meter →
What mounting options does PS7400 tuning fork support? How do I pick insertion length?
Does the PS7500 Na22 source really not need a license? How does it differ from Cs137?
Why is PS7600 microwave particularly sensitive to water-bearing media?
Microwave measurement leverages dielectric contrast: water has ε ≈ 80, while most solids are ε ≈ 2~10 — a 10× difference. PS7600 measures phase shift and amplitude attenuation of microwaves through the medium to recover water content, suspended solids concentration, density, and Brix. The strong dielectric contrast gives PS7600 high sensitivity in water-bearing applications — typical repeatability < ±0.01%. Best fit: power-plant limestone slurry, coal washing slurry, paper black liquor, sugar evaporator-crystallizer, food & beverage concentration. Not suitable for pure organic liquids (diesel, pure alcohols); use PS7020 or PS7110 instead.
By industry
Which density meter is recommended for power-plant FGD systems?
Typical Pisonics configurations for FGD:
- Limestone slurry tank / absorber recirculation → PS7400 tuning fork, excellent scaling resistance, range 1.0–1.4 g/cm³ covers all normal operating conditions
- Gypsum slurry / discharge pump downstream → PS7300 differential pressure, cost-effective for large-bore main lines
- FGD wastewater (high chloride) → PS7010 ultrasonic attenuation, clamp-on install removes the corrosion-protection problem
Final selection depends on your specific PFD, pipe sizes, temperature, and SO₃ content. Send us your process parameter sheet and we'll return a written sizing proposal within 2 business days.
Can density still be measured online when mining slurry exceeds 80°C?
Yes. Pisonics standard PS7400 tuning fork is rated 0–150°C; standard PS7000 ultrasonic is rated 0–120°C — covering most hydrometallurgical conditions. For extreme cases like high-pressure acid leach (HPAL) above 200°C, we offer customized high-temperature versions with titanium or Hastelloy wetted parts and remote-mounted transmitters to isolate the electronics.
Typical temperature tiers: ambient slurry (≤ 60°C) / heated flotation (60–90°C) / atmospheric leach (90–110°C) / pressure leach (150–250°C) / autoclave (≥ 250°C, special order). Tell us your upper temperature limit when requesting a quote.
Which density meter goes at each FGD measurement point?
Typical FGD configuration: limestone slurry tank / preparation discharge → PS7400 tuning fork (scale-tolerant) or PS7600 microwave (dielectric-sensitive); absorber gypsum slurry / discharge main → PS7000 (bubble-immune) or PS7300 differential pressure (large bore); FGD wastewater (high-chloride) → PS7010 clamp-on (no wetted parts) or PS7400 with titanium/Hastelloy fork; AFT tower high-concentration slurry → PS7000 or PS7500 Na22 nuclear; SCR ammonia / urea → PS7400 (mid-accuracy) or PS7100 spectroscopy (multi-component).
Mining hydrometallurgy slurry is hot and corrosive — can online meters still work?
Yes — Pisonics offers tiered temperature/corrosion solutions. Temperature tiers: ambient ≤ 60°C uses standard models; heated flotation 60~90°C uses standard high-temp variants; atmospheric leach 90~110°C uses dedicated high-temperature models; high-pressure acid leach (HPAL) 150~250°C requires custom titanium or Hastelloy wetted parts with remote-mounted transmitters; autoclave ≥ 250°C is special order. Corrosion: mild → 316L; strong acid/alkali → 2205 duplex, Hastelloy C-276, titanium, PTFE liners; high-abrasion slurry → ceramic probes + PTFE liner.
What sanitary requirements does food/brewing have, and can Pisonics meet them?
Sanitary requirements: (1) wetted materials — 316L polished (Ra ≤ 0.4 μm), PTFE, sapphire; (2) process connections — tri-clamp, ISO food-grade flanges; (3) CIP / SIP — withstand 90°C hot water, 3% NaOH / 3% HNO3 wash, 134°C steam; (4) crevice-free design; (5) compliance — FDA 21 CFR / EHEDG / 3-A (selected models). Pisonics sanitary variants: PS7400 (tri-clamp + 316L polished + PTFE), PS7110 (sapphire prism + tri-clamp), PS7020 (PTFE wetted + sanitary), PS7210 (tri-clamp).
Strong acids/bases (conc H2SO4 / NaOH / HCl) — which meter?
Material selection drives the choice: conc H2SO4 (98%) → PS7400 (PTFE-coated + titanium fork) or PS7110 (sapphire is acid-tolerant); NaOH (32% / 48%) → PS7400 (PTFE + 316L) or PS7100 (fiber-optic separated, controller in safe area); HCl → PS7100 (no wetted main body) or PS7110; mixed acids (H2SO4 + HNO3) → PS7100 (MLR simultaneously models both); HF → PS7100 or PS7110 (sapphire is HF-resistant). Simultaneous available chlorine + free NaOH in chlor-alkali sodium hypochlorite is a flagship PS7100 case.
Can Pisonics meters be used in pharma GMP / FDA validation?
Yes — GMP-compliant versions: (1) wetted parts — 316L electropolished, PTFE, sapphire; (2) process connections — sanitary tri-clamp (DIN 32676 / ISO 2852); (3) surface finish — Ra ≤ 0.4 μm mirror polish; (4) validation documentation — IQ / OQ documents, material certificates (EN 10204 3.1), surface roughness reports shipped with the unit; (5) CIP / SIP compatible — withstands 134°C steam sterilization. Typical applications: fermenter recirculation Brix/alcohol (PS7110), injection-grade concentration (PS7210), API crystallization (PS7300), PAT process analytics (PS7100). Successfully passed 21 CFR Part 11 audits.
What special requirements does oil & gas custody transfer impose?
Custody transfer requirements: (1) absolute accuracy — typically ≤ ±0.001 g/cm³, high-standard projects ≤ ±0.0005 g/cm³; (2) international approvals — OIML R117 / API MPMS 11.1 / MID; (3) long-term traceability — zero drift ≤ 0.0005 g/cm³ over 12 months, traceable to national metrology standards; (4) PT100 with real-time temperature/pressure correction; (5) thousands of transfer records in non-volatile buffer; (6) typically ExdⅡBT4 or above. Recommended: PS7400 (refined oil / LPG / marine fuel) and PS7210 Coriolis (high-accuracy metering).
What are the common challenges in municipal water / sludge density monitoring?
Challenges: (1) varied debris — fibers, hair, plastic fragments tangle on contact meters; (2) heavy fouling — sludge dewatering with phosphate / calcium deposits on probes; (3) corrosivity — sewage pH swings (4~10); (4) high gas content — aeration produces bubbles. Pisonics solutions: PS7000 acoustic impedance (gas-immune aeration basins), PS7010 clamp-on (retrofit non-tappable legacy lines, zero tangling), PS7400 with PTFE (sludge dewatering, vibration shakes off scale), PS7600 microwave (deep-dewatered sludge water content).
Do AI data centers need online ethylene glycol concentration monitoring?
Yes. AI data center liquid cooling (cold-plate, immersion) uses ethylene glycol (EG) or propylene glycol (PG) water solutions, typically 30~50%. Why monitor: too low → insufficient freeze-point margin, winter pipe-freeze risk; too high → viscosity climbs, pump power up, heat-transfer efficiency down. Drift sources: makeup water dilution; high-load evaporator zones preferentially lose water; gradual glycol oxidative degradation. Recommended: PS7400 tuning fork (±0.001 g/cm³ density, ±0.5% concentration), installed on the main heat-exchanger loop.
What does lithium-battery copper foil electrolyte monitoring require?
Core electrolyte: copper sulfate (CuSO4) + dilute sulfuric acid (H2SO4) + additives — concentration drives foil thickness uniformity, grain size, tensile strength. Challenges: (1) high corrosivity (H2SO4 + Cu2+); (2) narrow concentration window (CuSO4 typical 60~80 g/L, target ±2 g/L); (3) wide temperature swing (25~55°C); (4) trace additives (gelatin / SPS) interfere with certain principles. Recommended: PS7100 spectroscopy (MLR multi-component — Cu2+ + H2SO4 + additives in parallel) and PS7020 sound velocity (±0.0005 g/cm³ with PTFE liner).
How do density meters on dredging vessels cope with ship vibration and salt spray?
Challenges aboard dredging vessels: (1) continuous vibration — engine + pump + cutter generate 0.5~5g; (2) salt-spray corrosion — sea air attacks instrument housings; (3) coarse sand abrasion — slurry contains particles up to 50mm; (4) cross-border operations — radiometric meters trigger international transport permits. Recommended: PS7000 acoustic impedance — flanged insertion but non-contact probe (no abrasion); ceramic probe withstands ongoing sand impact (life ≥ 5 years); IP65 + ExdⅡCT6Gb optional; fully non-nuclear; optional 4G module for fleet-wide real-time monitoring.
Which density meter for paper-mill black / white liquor?
Black liquor (cooking spent liquor, lignin + alkali) and white liquor (NaOH / Na2S mixture) need concentration tracking for recovery efficiency and energy monitoring. Black liquor: high viscosity (500~3000 cP), dark color (optical methods unsuitable), 70~150°C, fine particles. Recommended: PS7600 microwave (water-sensitive dielectric, measures solids + concentration) or PS7020 sound velocity (color-immune). White liquor: strong alkaline corrosion, 80~120°C. Recommended: PS7110 refractometer (sapphire prism withstands NaOH) or PS7400 (PTFE coating). Green liquor (white liquor precursor): same as black liquor.
Which meter for TBM (tunnel boring machine) slurry balance?
Slurry-balance density is critical for face stability in slurry TBMs. Typical conditions: (1) feed slurry 1.05~1.20 g/cm³; (2) discharge slurry 1.20~1.40 g/cm³ (with excavated cuttings); (3) particles up to 50mm; (4) high vibration, humidity, moisture. Recommended PS7000 acoustic-impedance: flanged insertion but non-contact probe (no abrasion); ceramic probe withstands sand; Chirp algorithm bubble-immune; IP65 + ExdⅡCT6Gb optional; 4-20mA + Modbus feeds the TBM main PLC for real-time feed/discharge density differential and chamber pressure regulation.
What does semiconductor ultra-pure chemical concentration monitoring require?
Semiconductor wet processes (etching, CMP, cleaning) use ultra-pure chemicals (HF, H2SO4, H3PO4, KOH). Requirements: (1) wetted materials zero metal-ion contamination — sapphire, PTFE, Teflon-PFA; (2) high concentration accuracy (≤ 0.1 wt% deviation affects yield); (3) multi-component simultaneous (etch mix HF + HNO3 + H2SO4); (4) sanitary surface (prevent particle contamination); (5) long-term stability (24/7 fab operation). Recommended: PS7100 spectroscopy (multi-component MLR, no wetted main body, sapphire window), PS7110 refractometer (sapphire withstands HF), PS7020 sound velocity (PTFE wetted, acid-resistant).