How to Calibrate & Verify the A&D FX-300i
- pete8781
- Jul 31
- 3 min read
Need more details or help choosing the correct item? Call MNM Scales at (832) 290-3120 or email mnmscales@yahoo.com.
A&D FX-300i calibration uses an external calibration weight, so the correct procedure begins with warm-up, level and environmental stability before zero and span are adjusted.
FX-i versus FZ-i calibration: know which model you have
A&D’s manual covers both FZ-i and FX-i models, but their calibration hardware is different. FZ-i models have an internal mass and support one-touch automatic calibration. FX-i models such as the FX-300i do not have that internal mass; they use external calibration. Following FZ-i instructions on an FX-300i will cause confusion because the expected internal-calibration operation simply is not present.
Warm up for at least 30 minutes
A&D instructs users to connect power and warm the balance for at least 30 minutes with nothing on the pan before calibration. During that period, place it on a firm level surface away from drafts, vibration, sunlight and temperature changes. Milligram balances respond to small environmental effects, so a calibration performed immediately after moving the unit from a cold storage area can simply lock a transient temperature error into the span.
Verify the balance before changing calibration
After warm-up, zero the balance and place a known test weight near the center of the pan. Repeat the placement several times. A consistent offset indicates a possible calibration need; scatter from one reading to the next suggests drafts, vibration, static, sample temperature or mechanical interference. Verification protects against unnecessary recalibration and provides evidence about whether the problem is systematic or unstable.
Enter external calibration mode
A&D’s manual shows the FX-i external calibration sequence beginning by holding CAL until the display indicates the external calibration mode. The balance then captures the zero point with an empty pan. Once zero is accepted, the operator applies the selected external calibration weight and allows the indication to stabilize before the span value is stored. Follow the exact key prompts in the manual for the installed firmware rather than improvising from a different A&D model family.
Use a suitable calibration weight
Use a clean calibration or reference mass with known accuracy appropriate to the balance and your quality requirement. MNM’s FX-300i listing says a 100 g calibration weight is included, but the best calibration point for a specific procedure should follow A&D’s permitted weight settings and your verification plan. A random object with a nominal printed weight is not a calibration standard. Handle proper weights with clean tools or gloves when small mass changes matter.
Post-calibration verification
After calibration, verify zero return, repeatability and multiple points if the balance supports critical work. If the typical samples are 20–80 g, include a known weight in that region. If samples extend near 300 g, include a higher point as well. The objective is to demonstrate suitable performance across the actual working range, not just at the one point used to set span. Record the before/after results when calibration is part of a quality system.
Troubleshooting unstable milligram readings
At 0.001 g readability, drafts and static are common problems. Use a breeze break when necessary, especially around small open containers. Plastic samples and low humidity can create electrostatic forces. Warm samples cause convection. Vibrating refrigeration equipment, pumps or nearby machinery can move the last digits continuously. Solve these conditions before recalibrating. If readings remain unstable under controlled conditions, inspect the pan and arrange professional service.
Gravity and relocation
Precision balances can show a location-dependent change because local gravitational acceleration varies geographically. When the FX-300i is moved to a substantially different location, re-level, stabilize and calibrate it with a physical reference weight at the point of use. That real-weight calibration accounts for local gravity in the resulting span. A&D also recommends calibration after moving or significant environmental change.
FAQ
Does the FX-300i calibrate itself internally?
No. It is the external-calibration FX-i version. FZ-i models are the ones with internal calibration masses.
How long should it warm up?
A&D specifies at least 30 minutes before calibration.
Can I use the included 100 g weight?
MNM’s listing says a 100 g calibration weight is included. Use it only if its accuracy and the manufacturer’s allowed calibration settings meet your procedure’s requirements.
Why do the last digits move?
Common causes are drafts, vibration, static, temperature gradients and unstable samples. A 1 mg balance makes small environmental effects visible.
Should calibration be checked after moving the balance?
Yes. Re-level and verify after relocation, and calibrate as needed according to A&D guidance and your quality procedure.
Is calibration the same as legal-for-trade certification?
No. Calibration addresses measurement relationship; legal-for-trade approval is a separate regulatory status tied to the exact model/configuration.
Comments