Rainbow-electronics DS1920 Manual do Utilizador descarregar pdf (Página 5)

DS1920

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The most significant (sign) bit is duplicated into all of the bits in the upper MSB of the 2-byte

temperature register in memory. This “sign-extension” yields the 16-bit temperature readings as shown in

Table 1.

Higher resolutions may be obtained by the following procedure. First, read the temperature, and truncate

the 0.5°C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter

may then be read. This value is the count remaining (COUNT_REMAIN) after the gate period has

ceased. The last value needed is the number of counts per degree C (COUNT_PER_C) at that

temperature. The actual temperature may be then be calculated by the user using the following formula:

TEMPERATURE = TEMP_READ - 0.25 +

CCOUNT_PER_

IN)COUNT_REMA-_C(COUNT_PER

TEMPERATURE MEASURING CIRCUITRY Figure 3

TEMPERATURE/DATA RELATIONSHIPS Table 1

TEMPERATURE

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+100°C

00000000 11001000 00C8H

+25°C

00000000 00110010 0032H

+½°C

00000000 00000001 0001H

+0°C

00000000 00000000 0000H

-½°C

11111111 11111111 FFFFH

-25°C

11111111 11001110 FFCEH

-55°C

11111111 10010010 FF92H

SET/CLEAR

LSB

1 2 3 4 5 6 7 8 9 10 ... 21 22

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