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參數(shù)資料
| 型號(hào)： | LM34C |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 溫度/濕度傳感器 |
| 英文描述： | Precision Fahrenheit Temperature Sensors |
| 中文描述： | 精密華氏溫度傳感器 |
| 文件頁數(shù)： | 5/10頁 |
| 文件大?。?/td> | 242K |
| 代理商： | LM34C |
Typical Applications
The LM34 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or
cemented to a surface and its temperature will be within
about 0.02
§
F of the surface temperature. This presumes
that the ambient air temperature is almost the same as the
surface temperature; if the air temperature were much high-
er or lower than the surface temperature, the actual temper-
ature of the LM34 die would be at an intermediate tempera-
ture between the surface temperature and the air tempera-
ture. This is expecially true for the TO-92 plastic package,
where the copper leads are the principal thermal path to
carry heat into the device, so its temperature might be clos-
er to the air temperature than to the surface temperature.
To minimize this problem, be sure that the wiring to the
LM34, as it leaves the device, is held at the same tempera-
ture as the surface of interest. The easiest way to do this is
to cover up these wires with a bead of epoxy which will
insure that the leads and wires are all at the same tempera-
ture as the surface, and that the LM34 die’s temperature will
not be affected by the air temperature.
The TO-46 metal package can also be soldered to a metal
surface or pipe without damage. Of course in that case, the
V
b
terminal of the circuit will be grounded to that metal.
Alternatively, the LM34 can be mounted inside a sealed-end
metal tube, and can then be dipped into a bath or screwed
into a threaded hole in a tank. As with any IC, the LM34 and
accompanying wiring and circuits must be kept insulated
and dry, to avoid leakage and corrosion. This is especially
true if the circuit may operate at cold temperatures where
condensation can occur. Printed-circuit coatings and var-
nishes such as Humiseal and epoxy paints or dips are often
used to insure that moisture cannot corrode the LM34 or its
connections.
These devices are sometimes soldered to a small, light-
weight heat fin to decrease the thermal time constant and
speed up the response in slowly-moving air. On the other
hand, a small thermal mass may be added to the sensor to
give the steadiest reading despite small deviations in the air
temperature.
Capacitive Loads
Like most micropower circuits, the LM34 has a limited ability
to drive heavy capacitive loads. The LM34 by itself is able to
drive 50 pF without special precautions. If heavier loads are
anticipated, it is easy to isolate or decouple the load with a
resistor; see Figure 3. Or you can improve the tolerance of
capacitance with a series R-C damper from output to
ground; see Figure 4. When the LM34 is applied with a
499
X
load resistor (as shown), it is relatively immune to
wiring capacitance because the capacitance forms a bypass
from ground to input, not on the output. However, as with
any linear circuit connected to wires in a hostile environ-
ment, its performance can be affected adversely by intense
electromagnetic sources such as relays, radio transmitters,
motors with arcing brushes, SCR’s transients, etc., as its
wiring can act as a receiving antenna and its internal junc-
tions can act as rectifiers. For best results in such cases, a
bypass capacitor from V
IN
to ground and a series R-C
damper such as 75
X
in series with 0.2 or 1
m
F from output
to ground are often useful. These are shown in the following
circuits.
Temperature Sensor,
Single Supply,
b
50
§
to
a
300
§
F
TL/H/6685–6
TL/H/6685–7
FIGURE 3. LM34 with Decoupling from Capacitive Load
TL/H/6685–8
FIGURE 4. LM34 with R-C Damper
Temperature Rise of LM34 Due to Self-Heating (Thermal Resistance)
Conditions
TO-46,
No Heat Sink
TO-46,
TO-92,
No Heat Sink
TO-92,
SO-8
SO-8
Small Heat Fin
*
Small Heat Fin
**
No Heat Sink
Small Heat Fin
**
Still air
Moving air
Still oil
Stirred oil
(Clamped to metal,
infinite heat sink)
720
§
F/W
180
§
F/W
180
§
F/W
90
§
F/W
180
§
F/W
72
§
F/W
72
§
F/W
54
§
F/W
324
§
F/W
162
§
F/W
162
§
F/W
81
§
F/W
252
§
F/W
126
§
F/W
126
§
F/W
72
§
F/W
400
§
F/W
190
§
F/W
200
§
F/W
160
§
F/W
(43
§
F/W)
(95
§
F/W)
*
Wakefield type 201 or 1
×
disc of 0.020
×
sheet brass, soldered to case, or similar.
**
TO-92 and SO-8 packages glued and leads soldered to 1
×
square of
(/16
×
printed circuit board with 2 oz copper foil, or similar.
5
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM34CA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Precision Fahrenheit Temperature Sensors |
| LM34CAH | 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 |
| LM34CAH/NOPB | 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 |
| LM34CAHNOPB | 制造商:National Semiconductor 功能描述:Temp Sensor Analog Serial (2-Wire) 3-Pin TO-46 |
| LM34CAZ | 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 |
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