Sunday, April 7, 2013
Precision Fahrenheit Temperature Sensors Using LM34 IC’s
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 LM34 can be applied easily in the same way as other IC 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 higher or lower than the surface temperature, the actual temperature of the LM34 die would be at an intermediate temperature between the surface temperature and the air temperature.
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. The schematic for temperature controller using LM34 is in the figure.
Thursday, April 4, 2013
Precision Temperature Sensor IC LM35 Explained Celsius Sensor
The IC LM35 is a precision temperature sensor device, which generates linearly proportional output in response to the rising or falling ambient temperature, directly in Celsius.
Understanding the Specs of Temperature Sensor IC LM35
This feature of producing outputs directly in Celsius gives this device an significant edge over the other types of sensors which are based on degree Kelvin, where a conversion to Celsius becomes a relatively complex issue.
The IC LM35 does not need any external setting or adjustments for obtaining accurate results within +/-1/4 degree Celsius at temperatures of room level and at +/-3/4 degree Celsius between a complete -55 to +150 degree Celsius range of temperature.
The IC LM35 has features like linearly varying output, low output impedance and precise built-in calibration arrangement which makes the device very easy and ideally suitable for interfacing with all types of control circuits.
The IC is able to function with dual supplies or even with single polarity power supplies.
A low 60 uA consumption by this IC inhibits the IC from self heating, which amounts to 0.1 degree Celsius in constant air.
The IC LM35 has a good -55 degrees to +150 degrees Celsius sensing range.
The IC comes in a hermetically sealed TO-46 package, other ICs in the series like the LM35C, LM35CA, and LM35D come in the transistor type package of TO-92.
The LM35D comes also in the 8-pin surface laid small outline package and in TO-220 enclosure.
