ECL and the USP Minimum Weight Standard

ECL, which stands for Electronically Controlled Load, is A&D's patented
technology for generating a minute load (0.3 to 3% of the balance capacity) by
purposely altering the equilibrium state of the electromagnetic force

restoration sensor. A balance with this technology, such as the Apollo GX-AE/A & GF-A
series, allows the user to test its repeatability performance without using an external
weight by automatically calculating the standard deviation from 10 repeatedmeasurements with the said artificially generated load. Further, based on the result of
this repeatability test, the balance indicates the minimum weight with a tolerance ofeither 0.1% in accordance with the United States Pharmacopeia (USP), Chapter 411, or1%, depending on the laboratory requirements. Currently, ECL can complete a
repeatability test and minimum weight calculation in about a minute and a half.
While the principle of load sensing is exactly the same for ECL and an external weight,
users may question the validity of the minimum weight produced by the former, as it isdifficult to argue that ECL is the same as the "test weight" in the USP terms. They may
also point to the fact that with ECL the influence of the operator skill on repeatability
isn't taken into account. To such users, A&D answers as follows:
The difference between a repeatability test using ECL and using an external weight islike the difference between calibration 2 using an internal (built-in) weight and using an
external weight. In order to officially ensure and report accuracy, the balance needs tobe calibrated using an external weight, because the correction can only be determinedby an external weight. On the other hand, internal calibration is a simplified, informal
method (the internal weight value can vary with time or during transportation, etc.).
However, it is highly useful for daily accuracy management as it requires a much
shorter time and absolutely no skill on the part of the operator.
Similarly, in order to strictly abide by the USP standard, A&D also advises that an
external weight be used to test for repeatability and the minimum weight. Meanwhile,
ECL provides a number of new and different benefits. Firstly, it is quick and easy, aswith internal calibration. Secondly, users who do not know how to calculate the12For more details, please refer to http://www.aandd.jp/support/materials/usp_balances.pdf
Sensitivity adjustment, to be more precise

minimum weight can still determine the minimum amount of sample they need toweigh to be sure that their results are reliable. This should be good enough for those
who are not required to document compliance with the USP standard, and much better
than using the value provided as "typical" in manufacturers' brochures, etc., because
the minimum weight (repeatability) is greatly affected by environmental disturbances3
and therefore must be assessed where the balance is actually set up.
Thirdly, even when users ultimately have to obtain the minimum weight with an
external weight, they can seek to make it as small as possible by finding the optimal
installation settings by drawing on ECL in advance. Finally, ECL is extremely handy fordaily performance management. For example, users may want to check repeatability
three times a day (e.g. in the morning, afternoon and evening), which will be difficult if
they are to use an external weight. Additionally, it is troublesome for many users toprepare, maintain and handle an appropriate test weight, which is often small (notmore than 5% of the balance capacity).
With the above being said, when users require, the Apollo GX-AE/A & GF-A series canalso automatically calculate the minimum weight from 10 repeated measurements of anactual, external weight (and again, with a tolerance of either 0.1% or 1%).
A&D has long adhered to the policy of providing users with solutions that enable themto manage balance accuracy and performance easily by themselves while also trying toraise awareness that balance accuracy and performance are inseparable fromenvironmental factors. This is why A&D developed such products as the AD-1687
weighing environment logger, the AD-1691 weighing environment analyzer, and various
accessories to minimize the effects of external disturbances. ECL is one more of A&D'sefforts to pursue this policy.

A&D's experiments show that ECL and an external weight produce comparable minimum weights
under varying environmental conditions. Please inquire for details.
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