Why Every Balance Is Calibrated Where It Is Used — and What Should Happen Before First Use

A balance measures force, and gravity is not the same everywhere

An electronic balance does not weigh mass directly. It measures the force the sample exerts on the pan and converts that force into a mass reading using a factor set during calibration. The force depends on the local acceleration due to gravity, and that varies measurably across the Earth — it is slightly stronger nearer the poles and weaker nearer the equator, weaker at altitude, and different again between the ground floor and the tenth. The differences are small fractions of a percent, invisible on a kitchen scale and decisive on an instrument that resolves 0.01 g or 0.1 mg.

So a balance span-calibrated in one place carries that place's gravity in its conversion factor. Set it up somewhere else and it reads consistently, precisely, and slightly off — until it is calibrated where it stands. Every manufacturer's manual says the same thing for the same reason; it is physics, not a mark against any brand.

What should happen before first use

Let the balance sit powered on until it has reached room temperature — around thirty minutes for a precision balance, longer for an analytical one. Level it on its built-in spirit level before anything else; a balance that is not level reads low. Close the draught shield if it has one and keep it out of the direct air-conditioning stream. Then calibrate: on an internally calibrating model, run the calibration routine; on an externally calibrating model, place a certified reference weight on the pan and run it. Check the reading against the weight afterwards, and keep a record — model, serial, weight used, date, result.

That record is worth having from day one. It is the first entry in the balance's calibration history, it is what an auditor asks for, and it is what our calibration service builds on when it issues a certificate at installation or later: instrument, reference standards used, test points, results. A&D Gulf is not an ISO/IEC 17025-accredited laboratory; where your quality system requires an accredited certificate, tell us before you order and we will say so plainly.

Why the reference weight matters

An external calibration is only as good as the mass placed on the pan. A calibration weight with a certificate has a stated value and a stated uncertainty; a weight without one is a guess, and the balance will faithfully calibrate itself to the guess. Buy a weight of the class your balance resolves — the A&D calibration-weight ranges are listed by class — of at least the capacity you use most, and keep it with the balance rather than in a drawer two rooms away. A 3.2 kg counter balance is well served by a 1 kg or 2 kg certified weight.

How internal calibration removes the job

An internally calibrating balance carries its own reference mass inside the housing and loads it onto the mechanism on command: a motor-driven loader on the GH and BM series, an air-pump actuator on the Fortis FZ and FZ-i, and automatic self-calibration — A&D calls it ASC — on the GX-A, GX-M and GX-L, which fires when the detected room temperature moves beyond a set band, at a set interval, or at preset times. Because the internal mass is measured under the gravity of the room the balance is standing in, the span is re-anchored where it matters, without a weight and without anyone remembering. The result is logged through the GLP/GMP output.

That is the whole case for the GX-3002A over the GF-3002A, the FZ-3000i over the FX-3000i, the GH over an externally calibrated analytical balance: not higher accuracy, but accuracy that stays put in a room with cycling air-conditioning, a balance that moves between sites, or a laboratory that has to show a record. Where the bench is stable and someone owns the weight, the externally calibrated twin does the same work for less.

When to calibrate again

After the balance is moved — to another bench, another floor, another building. After it is serviced or repaired. After a large temperature change in the room. And at the interval your quality system sets, typically annually with a certificate and more often with a quick check against your own weight. Between calibrations, a daily check with the same reference weight tells you in ten seconds whether anything has changed.