How to Calibrate & Verify the A&D FX-500i
- pete8781
- Jul 31
- 3 min read
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A&D FX-500i calibration uses external reference weights rather than an internal calibration mass. MNM lists accepted values of 500, 400, 300, 200, 100 and 50 g. A&D’s FX/FZ-i manual recommends about 30 minutes of powered warm-up before precision use, and the manufacturer performance specification is 0.001 g repeatability with ±0.002 g linearity. Good calibration practice therefore includes environment control, a suitable reference mass and independent verification at more than one point when the process is demanding.
Warm-up and installation
Level the balance on a rigid bench and protect it from airflow, vibration, direct sun and changing temperature. Let calibration masses reach room temperature and power FX-500i for at least about 30 minutes. At 0.001 g readability, static on plastic vessels and convection around warm/cold samples can create larger errors than the display division. Correct the environment before adjusting calibration.
Accepted external calibration masses
MNM lists 500, 400, 300, 200, 100 and 50 g. Select a known reference with suitable uncertainty for the method, and use a larger mass when practical to establish span strongly. Place it carefully at the center of the 130 mm pan and avoid touching the table while the calibration point is captured. If traceability matters, keep the reference weight’s calibration status in the measurement system records.
Verify after CAL
Remove the calibration mass, confirm zero, then apply an independent known weight. For demanding work, test low, mid and high points and repeat a key load several times. Calibration adjusts the span relationship; verification demonstrates whether the whole system—including environment and mechanics—meets the acceptance tolerance. Retain pre-adjustment verification when investigating drift so the history is not erased.
Repeatability and linearity checks
A&D lists 0.001 g repeatability and ±0.002 g linearity. If repeated measurements spread more than expected, look for vibration, airflow, static, temperature and pan contact. If error changes with load, perform a multi-point test and service the balance if necessary rather than repeatedly calibrating at one point. The stated specification provides a benchmark; the facility’s acceptance tolerance must account for reference-weight uncertainty and actual conditions.
Eccentric loading and container contact
Large sample dishes or fixtures can contact the housing/bench, especially on a 130 mm pan. Compare a known weight at the center and representative off-center positions if the application uses awkward loads. A large position-dependent difference points to mechanical contact, pan seating, leveling or damage. A center-span calibration cannot correct a load that is partly supported elsewhere.
Static and drift troubleshooting
If the reading changes when a hand approaches a plastic container, static is likely. If it changes when HVAC starts, airflow/vibration may be responsible. If a cold sample slowly changes after placement, thermal convection or evaporation may dominate. Use antistatic controls, appropriate shielding and stable sample temperature before deciding the balance requires recalibration.
When to recalibrate
Recalibrate after relocation when required by the SOP, at scheduled intervals, or when controlled verification shows a consistent span error. Routine verification is usually the better first response to a suspected issue because it preserves evidence. If the last digit simply fluctuates in a changing environment, recalibration may make the displayed number different without fixing the real cause.
External calibration does not make FX-500i NTEP
A&D’s current U.S. model matrix has no FX-500iN and does not identify FX-500i as an NTEP model. A calibrated and qualified FX-500i can be excellent for regulated laboratory processes, but that is different from legal-for-trade type approval. If a customer transaction is based on weight, use a specifically certified model/configuration.
Frequently asked questions
Does FX-500i have internal calibration? No. What masses can calibrate it? MNM lists 500, 400, 300, 200, 100 and 50 g. How long should it warm up? About 30 minutes. Repeatability/linearity? 0.001 g and ±0.002 g. Should CAL be followed by verification? Yes. What if results differ by pan position? Check eccentric loading/mechanical contact. What if the display drifts with a plastic vessel? Investigate static. Does calibration make FX-500i NTEP? No.
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