DA5534_022.doc
July 17th, 2002
10
ECN493
Example:
Word1, Word2, Word3 and Word4 (4x16 Bit)
D1 = 17000
D2 = 22500
Start
Convert calibration data into coefficients:
(see bit pattern of Word1-Word4)
Read calibration data (factory calibrated) from
PROM of MS5534
Read digital pressure value from MS5534A
D1 (16 Bit)
Read digital temperature value from MS5534A
Display pressure and temperature value
Basic equations:
Calculate calibration temperature
UT1=8*C5+20224
Calculate temperature compensated pressure
Difference between actual temperature and reference
temperature:
dT = D2 - UT1
Actual temperature in °C:
TEMP = (200 + dT*(C6+50)/2
10)/10
Calculate actual temperature
D2 (16 Bit)
SENST1
OFFT1
TCS
TCO
Tref
TEMPSENS
C1: Pressure sensitivity
(15 Bit)
C2: Pressure offset
(12 Bit)
C3: Temperature coefficient of pressure sensitivity (10 Bit)
C4: Temperature coefficient of pressure offset
(10 Bit)
C5: Reference Temperature
(11 Bit)
C6: Temperature coefficient of the temperature
(6 Bit)
Word1 = 50426
Word2 = 9504
Word3 = 48029
Word4 = 55028
C1 = 25213
C2 = 1908
C3 =
859
C4 =
750
C5 =
148
C6 =
32
dT(D2) = D2 - Tref
TEMP(D2)=20°+dT(D2)*TEMPSENS
Offset at actual temperature:
OFF = C2*4 + ((C4-512)*dT)/2
12
Sensitivity at actual temperature:
SENS = C1 + (C3*dT)/2
10 + 24576
X = (SENS * (D1-7168))/2
14 - OFF
Temperature compensated pressure:
P = X*100/2
5 + 250*100 (0.01mbar resolution)
P = X*10/2
5 + 250*10
(0.1mbar resolution)
OFF(D2)=OFFT1+TCO*dT(D2)
SENS(D2)=SENST1+TCS*dT(D2)
P(D1,D2)=D1*SENS(D2)-OFF(D2)
dT
= 1092
TEMP = 287
= 28.7 °C
OFF
= 7695
SENS = 50705
X
= 22732
P
= 96037
= 960.37 mbar
Fig. 3: Flow chart for pressure/temperature reading and software compensation.
Notes:
1.
Readings of D2 can be done less frequently, but the display will be less stable in this case
2.
For a stable display of 0.1mbar resolution, it is recommended to display the average of 8 subsequent
pressure values.
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