DA5541-30C_001.doc

Sept. 25th, 2008

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0005541C1348 ECN1143

Example:

Word1, Word2, Word3 and Word4 (4x16 Bit)

D1 = 15380

D2 = 22027

Start

Convert calibration data into coefficients:

(see bit pattern of Word1-Word4)

Read calibration data (factory calibrated) from

PROM of MS5541-30

Read digital pressure value from MS5541-30

D1 (16 Bit)

Read digital temperature value from MS5541-30

Display pressure and temperature value

Basic equations:

Calculate calibration temperature

UT1=8*C5+10000

Calculate temperature compensated pressure

Difference between actual temperature and reference

temperature:

dT = D2 - UT1

Actual temperature:

TEMP = 200 + dT*(C6+100)/2

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(0.1°C)

Calculate actual temperature

D2 (16 Bit)

SENST1

OFFT1

TCS

TCO

TEMPSENS

C1: Pressure sensitivity

(13 Bit)

C2: Pressure offset

(13 Bit)

C3: Temperature coefficient of pressure sensitivity (10 Bit)

C4: Temperature coefficient of pressure offset

(9 Bit)

C5: Reference Temperature

(12 Bit)

C6: Temperature coefficient of the temperature

(7 Bit)

Word1 = 46076

Word2 = 14170

Word3 = 39937

Word4 = 33721

C1 = 5759

C2 = 4317

C3 =

624

C4 =

263

C5 = 1665

C6 =

57

TEMP(D2)=20°+dT(D2)*TEMPSENS

Offset at actual temperature:

OFF = C2 + ((C4-250)*dT)/2

Sensitivity at actual temperature:

SENS = C1/2 + ((C3+200)*dT)/2

Temperature compensated pressure in mbar:

P = (SENS * (D1-OFF))/2

OFF(D2)=OFFT1+TCO*dT(D2)

SENS(D2)=SENST1+TCS*dT(D2)

P(D1,D2)=D1*SENS(D2)-OFF(D2)

dT

= -1293

TEMP = 101

= 10.1 °C

OFF

= 14312

SENS = 5749

P

= 3998

= 3998 mbar

UT1 = 23320

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 1 mbar resolution, it is recommended to display the average of 4 to 8 subsequent

pressure values.