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FM50 数据表(PDF) 5 Page - Fairchild Semiconductor |
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FM50 数据表(HTML) 5 Page - Fairchild Semiconductor |
5 / 8 page PRODUCT SPECIFICATION FM50 REV. 1.0.8 9/12/02 5 Applications Information Although the FM50 is a simple device, care must be taken to ensure that temperature is measured accurately. There are two major sources of errors: 3. Voltage errors. 4. Thermal Delay Errors. 5. Location errors Voltage Errors Figure 4. Recommended Electrical Connections A Kelvin connection is recommended to avoid errors due to voltage drops in the ground connections. Although the typical 130µA supply current draw of the FM50 will only cause a 130µV error if the series resistance is 1 Ω, a 100 mA current supply to adjacent circuits can cause a 10mV drop across 100m Ω (10mΩ is a typical value for soldered joints or contact resistance), leading to a 1°C error. For this reason, the FM50 should be Kelvin connected as shown in Figure 4. Thermal Delay Errors For measurement accuracy of the order of tenths of 1°C, adequate settling time must be allowed. For a typical circuit board installation, 15 minutes should be allowed to elapse following reading of temperature within 1 - 2°C of the expected final value. Once VOUT has ceased to slew and is stable (with or without about ±0.1°C noise) for about 5 minutes, temperature can be calculated. Location Errors Position is another source of error. Even within a controlled thermal environment, changing location by a few inches can lead to errors of several tenths of 1°C Mounting The FM50 can be easily mounted by gluing or cementing it to a surface. In this case, its temperature will be within about 0.2°C of the temperature of the surface it is attached to if the ambient air temperature is almost the same as the surface temperature. If the air temperature is much higher or lower than the surface temperature, the actual temperature of the FM50 die will be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity, the backside of the FM50 die is directly attached to the GND pin. The lands and traces to the FM50 will, of course, be part of the printed circuit board, which is the object whose temperature is being measured. These printed circuit board lands and traces will not cause the FM50’s temperature to deviate from the desired temperature. Alternatively, the FM50 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 FM50 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 conden- sation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paint or dips can be used to ensure that moisture cannot corrode the FM50 or its connections. FM50 VDD VOUT GND(power) GND(sense) |
类似零件编号 - FM50 |
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类似说明 - FM50 |
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