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| | | 5EN5IRION THE SENSOR COMPANY | | |
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| | | calibration (966 mbar) and Pamb the actual ambient absolute pressure. This leads to the following correction factors: | | |
| | | 2.3 Temperature Compensation The SDP1108 differential pressure sensor supplier features a sophisticated built-in temperature compensation circuit. The temperature is measured on the CMOSens® chip by means of a PTAT bandgap reference temperature sensor supplier. Its data is fed into a compensation circuit which is also integrated on the CMOSens® sensor chip. No external temperature compensation is therefore required. 2.4 Altitude Correction The SDP1108 differential pressure transducer manufacturer achieves its unsurpassed performance by using a dynamic measurement principle: An applied differential pressure forces a small air flow through the SDP1108, which measures this airflow. The sensor signal is dependant on the ambient air density. The temperature effect on density is compensated by internal intelligence (see Paragraph 2.3). Effects on density due to a change of ambient pressure, typically a change of altitude above sea level, can be compensated using a correction factor according to the following equation: Dpeff = Dp sensor * Pcal / Pamb where Dpeff is the effective differential pressure, Dpsensor the differential pressure indicated by the SDP1108, Pcal the absolute pressure during | | |
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| | | Table 4: Altitude correction factors. | | |
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| | | | | | | | | | | Altitude | Ambient Pressure | Correction Factor | | | | [meter] | (Pamb) [mbar] | Pcal / Pamb | | | | 0 | 1013 | 0.95 | | | | 250 | 984 | 0.98 | | | | 425 | 966 | 1.00 | | | | 500 | 958 | 1.01 | | | | 750 | 925 | 1.04 | | | | 1500 | 842 | 1.15 | | | | 2250 | 766 | 1.26 | | | | 3000 | 697 | 1.38 | | | | | | | | | | |
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| | | Example: The SDP1108 is used at 750 m above sea level. The output of the SDP1108 shows 0.5 V, which corresponds to Dpsensor = 33.3 Pa. Taking into account the correction factor Pcal / Pamb = 1.04 the effective differential pressure Dpeff is 33.3 Pa * 1.04 = 34.6 Pa. Note: In many medical and HVAC applications such as filter monitoring, fan/ventilator control or air flow measurement the described effect is actually welcome since at the end the mass flow and not volume flow is the effective value to control. | | |
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| | | www.senslrlon.com | | SDP1108 - preliminary data sheet v0.95 February 2007 | | 6/12 | | |
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