MS5540C Datasheet, PDF (10/18 Pages) Intersema Sensoric SA – MINIATURE BAROMETER MODULE

Start
Read calibration data (factory calibrated) from
PROM of MS5540
Word1, Word2, Word3 and Word4 (4x16 Bit)
Basic equations:
Convert calibration data into coefficients:
(see bit pattern of Word1-Word4)
C1: Pressure sensitivity
C2: Pressure offset
C3: Temperature coefficient of pressure sensitivity
C4: Temperature coefficient of pressure offset
C5: Reference Temperature
C6: Temperature coefficient of the temperature
(15 Bit)
(12 Bit)
(10 Bit)
(10 Bit)
(11 Bit)
(6 Bit)
SENST1
OFFT1
TCS
TCO
Tref
TEMPSENS
Example:
Word1 = 46940
Word2 = 40217
Word3 = 25172
Word4 = 47212
C1 = 23470
C2 = 1324
C3 = 737
C4 = 393
C5 = 628
C6 = 25
Read digital pressure value from MS5540
D1 (16 Bit)
Read digital temperature value from MS5540
D2 (16 Bit)
Calculate calibration temperature
UT1 = 8*C5+20224
Calculate actual temperature
Difference between actual temperature and reference
temperature:
dT = D2 - UT1
Actual temperature:
TEMP = 200 + dT*(C6+50)/2¹⁰ (0.1°C resolution)
dT(D2) = D2 - T_ref
TEMP(D2) = 20°+dT(D2)*TEMPSENS
Calculate temperature compensated pressure
Offset at actual temperature:
OFF = C2*4 + ((C4-512)*dT)/2¹²
Sensitivity at actual temperature:
SENS = C1 + (C3*dT)/2¹⁰ + 24576
X = (SENS * (D1-7168))/2¹⁴ - OFF
Temperature compensated pressure:
P = X*10/2⁵ + 250*10 (0.1 mbar resolution)
OFF(D2) = OFFT1+TCO*dT(D2)
SENS(D2) = SENST1+TCS*dT(D2)
P(D1,D2) = D1*SENS(D2)-OFF(D2)
Display pressure and temperature value
D1 = 16460
D2 = 27856
UT1 = 25248
dT = 2608
TEMP = 391
= 39.1 °C
OFF = 5220
SENS = 49923
X = 23093
P = 9716
= 971.6 mbar
Fig. 3: Flow chart for pressure and 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 0.1 mbar resolution, it is recommended to display the average of 8 subsequent
pressure values.
DA5540C_003
June 16th, 2008
10
0005540C1193 ECN 1118