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High-Accuracy Calibration for a Specialized Low Flow Flow Meter
Quick answer: A low flow meter below 10 kg/h often drifts 2–5 % if calibrated with standard big-rig master meters. We use a gravimetric bench with a 0.02 % reading uncertainty and DN2–DN6 lines to get real accuracy within 0.1 % of rate. Send us your fluid viscosity, minimum flow in kg/h, and pipe size for a fixed-price calibration protocol.
Why Low Flow Calibration Demands a Different Approach
Calibrating a full-bore DN50 Coriolis meter at 20,000 kg/h is straightforward. You bolt it onto a master meter skid, run water, and compare pulses. That method fails when your flow span is 0.05 to 5 kg/h. The dead volume alone in a standard manifold can hold more fluid than your small meter sees in one minute. Thermal mass, pressure drop changes, and even the weight of the cabling can shift the zero.
Low flow calibration is not just about a smaller reference. It is about controlling variables that are invisible at higher flows. We learned this over 12 years while calibrating gear meters for additives, Coriolis micro-bend sensors for catalyst injection, and thermal mass meters for biogas research. The core rule: the reference standard must be at least four times better than the device under test, and the whole loop must be leak-tight at 80 bar with a temperature stability of ±0.1 °C during the run.
Micro Flow Meters We Regularly Calibrate
Most of our calibration orders come from engineers running pilot plants, dosing skids, and R&D labs. The typical devices we handle include:
Micro oval gear meters for solvents and monomers, down to 0.008 L/h. Coriolis mass flow meters like the Silver Instruments M08 series, covering 0–20 kg/h with a 0.05 % uncertainty in the lab. Thermal mass flow meters for argon and CO₂ purge lines, where the actual gas density at 1.2 bar changes the span by 0.3 %. And small electromagnetic flow meters for conductive fluids with a minimum conductivity of 5 µS/cm, often used in pharmaceutical water injection.
Inside Our Low Flow Calibration Bench
The bench we use is not a multi-purpose skid shared with 12-inch lines. It is a dedicated low-flow station with three interchangeable weigh scales: one 220 g balance with 0.1 mg resolution, one 6 kg platform, and one 30 kg comparator for mid-range crossover checks. The fluid path is 1/8 inch and 1/4 inch 316L tubing, electro-polished to Ra 0.4 to prevent bubble adhesion. We control the pump stroke with a servo-driven syringe array that eliminates pulsation, something a diaphragm metering pump cannot do at 0.5 kg/h.
Here is the thing: a single micro-bubble stuck in a DN3 tube can cause a 1.2 % density error on a Coriolis meter. That does not matter on a 2-inch line, but on a small sensor it ruins the calibration. So we fill the system with a vacuum-assisted prime and degas the test fluid for 45 minutes before starting. We log data at 10 Hz and compare gravimetric mass against pulse output, 4-20 mA HART, or Modbus RTU, depending on your transmitter. The whole sequence runs inside an enclosure stabilized at 22 °C ±0.2, because an ambient drift of 1 °C can mimic a 0.12 % zero shift on a micro Coriolis sensor.
Real Example: Paint Manufacturer in Southeast Asia
Last year a paint factory in Thailand asked us to calibrate six Coriolis meters used for harde
Calibration Data You Will Receive
Every meter leaves our lab with a traceable certificate following ISO 17025 principles. For each test point we report: reference mass (g), measured mass (g), deviation in % of rate, repeatability across five runs, and the expanded uncertainty with a k=2 coverage factor. If you need multi-viscosity testing, we provide a matrix across three different fluids typically 1 cP water, 10 cP oil, and 50 cP oil to build a Reynolds number correction curve. That curve lets your PLC apply a dynamic K-factor, which is far more robust than a single average factor.
Frequently Asked Questions
What is the smallest flow you can calibrate?
We handle liquid flows from 0.005 kg/h to 100 kg/h. Gas flows from 0.02 slpm to 50 slpm with a thermal reference. For lower flows we use a custom micro weigh method. Tell us your minimum expected flow and fluid and we will confirm capability.
Do you calibrate meters onsite?
We recommend lab calibration for micro flow. Onsite conditions rarely have the temperature stability needed. But for Australia, NZ, and ASEAN countries we can ship meters back within 10 working days including transport.
Which fluids can you use as the calibration medium?
We stock water, Isopar L, Shell Tellus 22, and propylene glycol. If your real fluid is hazardous or expensive, we can calibrate with a viscosity-matched surrogate and correct for density. Send us the MSDS and viscosity curve.
What traceability do your calibrations have?
All references are traceable to national standards through an accredited mass lab. The uncertainty chain is documented on the certificate. We also support customer audits over video call while the calibration runs.
How often should a low flow meter be recalibrated?
For meters dosing additives or catalysts, we recommend a 6-month interval. Zero drift alone can reach 0.15 % in 4 months on a hot skid. If your meter sees abrasive particles or aggressive solvents, check it every 3 months. We keep your calibration history free of charge so you can see drift trends.
Contact Silver Automation Instruments for a calibration quote.
Email: [email protected]
Tel: +86-25-68650347
Whatsapp: +86-25-52155837
WeChat: +86 15365082610
Request a quote: send us your fluid viscosity (cP), minimum and maximum flow rate (kg/h), pipe size (DN), and process temperature (°C). We reply with a calibration protocol and fixed price within one working day.