參數(shù)資料
型號(hào)： DS1820
英文描述： 1-Wire Digital Thermometer
文件頁(yè)數(shù)： 4/27頁(yè)
文件大?。?/td> 151K
代理商： DS1820
DS1820
030598 4/27
USING V
DD
TO SUPPLY TEMPERATURE CONVERSION CURRENT
Figure 3
+5V
DS1820
I/O
4.7K
μ
P
V
DD
TO OTHER 1–WIRE
DEVICES
EXTERNAL +5V SUPPLY
OPERATION – MEASURING TEMPERATURE
The DS1820 measures temperature through the use of
an on–board proprietary temperature measurement
technique. A block diagram of the temperature mea-
surement circuitry is shown in Figure 4.
The DS1820 measures temperature by counting the
number of clock cycles that an oscillator with a low tem-
perature coefficient goes through during a gate period
determined by a high temperature coefficient oscillator.
The counter is preset with a base count that corre-
sponds to –55
°
C. If the counter reaches zero before the
gate period is over, the temperature register, which is
also preset to the –55
°
C value, is incremented, indicat-
ing that the temperature is higher than –55
°
C.
At the same time, the counter is then preset with a value
determined by the slope accumulator circuitry. This cir-
cuitry is needed to compensate for the parabolic behav-
ior of the oscillators over temperature. The counter is
then clocked again until it reaches zero. If the gate
period is still not finished, then this process repeats.
The slope accumulator is used to compensate for the
non–linear behavior of the oscillators over temperature,
yielding a high resolution temperature measurement.
This is done by changing the number of counts neces-
sary for the counter to go through for each incremental
degree in temperature. To obtain the desired resolution,
therefore, both the value of the counter and the number
of counts per degree C (the value of the slope accumu-
lator) at a given temperature must be known.
Internally, this calculation is done inside the DS1820 to
provide 0.5
°
C resolution. The temperature reading is
provided in a 16–bit, sign–extended two’s complement
reading. Table 1 describes the exact relationship of out-
put data to measured temperature. The data is trans-
mitted serially over the 1–Wire interface. The DS1820
can measure temperature over the range of –55
°
C to
+125
°
C in 0.5
°
C increments. For Fahrenheit usage, a
lookup table or conversion factor must be used.
Note that temperature is represented in the DS1820 in
terms of a
1
/
2
°
C LSB, yielding the following 9–bit format:
MSB
LSB
1
1
1
0
0
1
1
1
0
= –25
°
C
The most significant (sign) bit is duplicated into all of the
bits in the upper MSB of the two–byte temperature reg-
ister 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
(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:
the
count
remaining
TEMPERATURE = TEMP_READ – 0.25
(COUNT_PER_C – COUNT_REMAIN)
COUNT_PER_C
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS1820K 制造商:Maxim Integrated Products 功能描述:THERMOMETER DEMO KIT
DS1820S 制造商:未知廠家 制造商全稱:未知廠家 功能描述:DS1820.DS1820S Digital Thermometer Replacements
DS1821 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
DS1821_07 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:Programmable Digital Thermostat and Thermometer
DS1821+ 功能描述:板上安裝溫度傳感器 Programmable Digital Thermostat/Thrmmtr RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
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