Arroyo Instruments ComboSource 6300 Series, Руководство пользователя

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Page 50 · 6300 Series ComboSource User’s Manual
As stated above, correction is done using a linear equation, and we need to
calculate the slope and offset. Slope must be calculated first, and is calculated
using the following formula:
Slope = (y
2
– y
1
) / (x
2
– x
1
)
For the set point calibration, ‘x’ is the actual current and ‘y’ is the set point. For
the measurement calibration, ‘x’ is the measurement and ‘y’ is the actual current.
Make sure to note how the actual current changes position depending on what
you are calibrating.
The offset is equally simple to calculate:
Offset = y
1
– Slope * x
1
So for the set point calibration, you would have the following two calculations:
Slope = (300 – 100) (298.6 – 101.5) = 200 / 197.1= 1.0147 (slightly rounded)
Offset = 100 – 1.0147 * 101.5 = − 2.9934
You can validate your calculations by applying the formula to one or both of the
data points to confirm the compensation is correct. Consider the 300mA set
point … if we apply the values just calculated, we should get a compensation
that increases the set point by slightly over 1.4mA to bring it up to 300mA. Let’s
check:
300mA test point = 1.0147 * 300 − 2.9934 = 301.4166mA – check!
Likewise, the 100mA set point should be
lowered by slightly more than 1.5mA:
100mA test point = 1.0147 * 100 − 2.9934 = 98.4766mA – check!
You can make the same tests of the measurement side. By using the multiple
point calibration, you benefit from the calibration across a much wider operating
range. When choosing your two data points, you can either calibrate specifically
for your application, where the upper point should be the maximum current you
plan to operate, and the lower data point near the minimum current you plan to
operate (but above zero). Alternatively, you can take two generalized data points
of 80% of the range of the instrument as the upper point and 20% of the range
as the lower point… this latter approach provides a more generated calibration
that will function across the full range of the instrument.
Accuracy Requirements
When calibrating the instrument, we recommend that the accuracy of your meter
is four times greater than the accuracy you are trying to achieve with the