USER MANUAL
FOR THE LM-34 A PRECISION FAHRENHEIT TEMPERATURE SENSORS
FUNCTION
MODULE
TABLE OF CONTENTS
LIST OF FIGURE
CAPTIONS
Figure 1 -- Circuit diagram for the LM34 temperature sensor
functional module
Figure 2 -- Package
Diagram of LM34
Figure 3 -- Labeled
picture of the temperature sensor circuit functional module.
Figure 4 -- Labeled
picture of the probe head.
LIST OF TABLE CAPTIONS
Table 1 -- Wiring directions for the temperature sensor
circuit
Table
2 -- Wiring directions for the function module of temperature
sensor
circuit.
Table 3 -- Apparatus Needed for Testing
Table 4 -- Required components
1. introduction
Temperature is the most-measured process variable in
industrial automation. Most
commonly, a temperature sensor is used to convert temperature value to an
electrical value. Temperature Sensors
are the key to read temperatures correctly and to control temperature in industrials applications.
A large distinction can be made between temperature sensor
types. Sensors differ a lot in
properties such as contact-way, temperature range, calibrating method and
sensing element. The temperature sensors
contain a sensing element enclosed in housings of plastic or metal. With the help of conditioning circuits, the sensor will reflect the
change of environmental temperature.
In the temperature functional
module we developed, we use the LM34 series of temperature sensors. The LM34
series are precision integrated-circuit temperature sensors, whose output
voltage is linearly proportional to the Fahrenheit temperature. The LM34 thus
has an advantage over linear temperature sensors calibrated in degrees Kelvin,
as the user is not required to subtract a large constant voltage from its
output to obtain convenient Fahrenheit scaling. The LM34 does not require any
external calibration or trimming to provide typical accuracies of ±1.2°F at room temperature and ±11.2°F over a full -50 to +300°F temperature
range. The LM34 is rated to operate over a -50° to +300°F temperature range.
Figure 1 Circuit diagram for the LM34 temperature
sensor functional module
It is easy to include the LM34 series in a
temperature measuring application. The output voltage of LM34 is linearly proportional to the Fahrenheit
temperature, it has a Linear +10.0 mV/°F scale factor which
means that you will get n*10.0 mV output
voltage if the environment temperature
is n°F.
The LM34 series is
available packaged in hermetic TO-46 transistor packages, while
the LM34C, LM34CA and LM34D are also available in the plastic TO-92 transistor
package. The LM34D is also available in an 8-lead surface mount small outline
package. In our functional module, LM34H in metal can package (TO-46) is used
in the functional module, it is very important to know that the wiring of
sensor should be based on the positions of the leading pins in different
packages.
Figure 2 Package Diagram of LM34
2. dESCRIPTION OF TEMPERATURE SENSOR
FUNCTIONAL MODULE
The temperature
sensor functional module consists of two parts: the function module box and the
probe head. The LM34 temperature sensor is mounted on the probe head. Be
careful to make sure that the sensor is properly mounted on the probe head. (refer
to Figure 4 Labeled picture of the probe head.)
Figure 3 Labeled picture of the temperature
sensor circuit functional module.
By replacing the LM34 with another precision
integrated-circuit temperature sensor LM35, we can easily get an output voltage
proportional to the centigrade temperature. The LM35 sensor has a linear +10.0
mV/°C scale factor and a temperature range from
-55°C to +150°C.In fact LM34 and LM35 are
among the same series of temperature sensors so that they can be easily
exchanged in different applications. The wiring for
LM 35 is the same as that of LM34. Please refer to the
datasheets of LM34 and LM35 for more detailed packaging and features information.
3. WIRING INSTRUCTIONS
Wiring of the LM34
temperature functional module consists of wiring of functional module box and
wiring of the sensor probe. The sensor is mounted on the probe head and the
probe is connected to the module box. For LM34 in metal
can package (TO-46), the small tab on the sensor indicates the position of “+Vs” leading pin (please refer to
Figure 2 and datasheet of LM34).
Figure 4 Labeled picture of the probe head.
Table 1 Wiring directions for the function module of temperature sensor circuit.
|
Red
|
Source voltage, 5V
|
|
Black
|
Ground voltage, 0V
|
|
Yellow
|
Output voltage signal
|
Table 2 Wiring directions for the probe
head.
|
Grey
|
Source voltage, 5V
|
|
Black
|
Ground voltage, 0V
|
|
White
|
Output voltage signal
|
4. APPARATUS
Table 3 Apparatus Needed for Testing
|
Digital multimeter, or equivalent ohmmeter, ammeter, and
voltmeter
|
|
Power source
|
|
Voltage box, with ground (0 volts), -15, +15, and +5 volt
outlets
|
5. List of parts
Table 4 Required components
|
Piece
|
Value
|
Unit
|
|
LM34 temperature sensor
|
N/A
|
N/A
|
|
Red wire
|
N/A
|
N/A
|
|
Black wire
|
N/A
|
N/A
|
|
Yellow wire
|
N/A
|
N/A
|
6. REFERENCES
NATIONAL
SEMICONDUCTORT . (2000) “LM34 Precision
Fahrenheit Temperature Sensors” NATIONAL SEMICONDUCTOR http://www.national.com/ds/LM/LM34.pdf
NATIONAL SEMICONDUCTORT
. (2000) “LM34 Precision Fahrenheit
Temperature Sensors” NATIONAL SEMICONDUCTOR http://www.national.com/ds/LM/LM35.pdf
RIZZONI, GIORGIO.
(2000) Principles and Applications of Electrical Engineering. 3rd
edition. Boston , MA
For word documentation please click HERE
