MicroStep-MIS MSB780X1D - More than 2 Pressure Points Adjustment

MSB780(X) - User’s Guide
1. Read the old k and q values, write them down.
2. Set the k and q values to default values, k = 1, q = 0 using cset<cr> command.
3. Compare the MSB780 or MSB780X reading against the reference at the first point, write
down the values. For example MSB780 or MSB780X: 750.12, reference: 750.35.
4. Compare the MSB780 or MSB780X reading against the reference at the second point,
write down the values. For example MSB780 or MSB780X: 1100.5, reference: 1099.30.
5. Compute the coefficients as follows:
k =
ref
2
− ref
1
msb
2
− msb
1
(2)
q = ref
1
− k ∗ msb
1
(3)
where:
ref
1
is the reference reading, lower pressure
ref
2
is the reference reading, higher pressure
msb
1
is the MSB780 or MSB780X reading, lower pressure
msb
2
is the MSB780 or MSB780X reading, higher pressure
Example values:
k =
1099.3 − 750.35
1100.5 − 750.12
=
348.95
350.38
= 0.995919 (4)
q = 750.35 − 0.995919 ∗ 750.12 = 3.291 (5)
6. Write the new k and q values to MSB780 or MSB780X memory using command cset<cr>,
as documented in section 6.36 on page 49.
5.6 More than 2 pressure points adjustment
If you would like to adjust the barometer using more than 2 calibration points, it is required to
approximate the calibration points using a linear regression calculation. Since linear regression
is commonly known, we do not discuss it in detail.
To compute coefficients k and q, consider the MSB780 or MSB780X readings being x values and
corresponding reference values being the y values. Equations 6 and 7 should be used. Using
calculator, computer program or online calculator is advised. After computing the coefficients
they need to be stored in MSB780 or MSB780X memory the same way, as in previous section.
k =
P
n
i=1
x
i
y
i
− n¯x¯y
P
n
i=1
x
2
i
− n¯x
2
(6)
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