Sensor Installation Handbook Preface 3rd edition - Siemens ...

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Velocity 76 Measuring air velocity and air flow (Measured variable w = m/s) Velocity measurements based on effective differential pressure A fixed obstacle (orifice plate, flow nozzle etc.) placed in the air flow creates a pressure differential which varies according to flow velocity. The flow velocity can be determined by measuring this differential pressure and converting it appropriately. Special flow detectors are available for this purpose: Orifice plate Flow nozzle Flow cross Flow grid Hot-wire anemometer (thermoelectric) A heating element is heated to a given temperature. The heat output required to maintain this temperature varies according to the flow velocity. The required heat output is measured and converted into a flow velocity. Important: The hot-wire anemometer is only suitable for spot measurements.
Measuring water velocity and flow Like air velocity, water velocity can be measured with orifice plates. Velocity measurements, however, are primarily required in order to determine heat volume. There are various commercially available heat meters, based on different mechanisms for measuring flow velocity. Example: Orifice Impeller Ultrasound Magnetic flux Inductiv Important: The required steadying zones must be allowed for, upstream and downstream of the sensor. Flow velocity To determine the flow velocity, the differential pressure at the flow detector (orifice plate, flow grid etc.) is measured. The same general mounting instructions apply as for differential pressure sensors. Important: The required steadying zones must be allowed for, upstream and downstream of the sensor. Formula: dg = Equivalent diameter Velocity 77
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Sensor Installation Handbook Prefac
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Sensor Installation Handbook Prefac
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General notes for all sensors Alway
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Always allow a sufficient length of
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Temperature Immersion sensors · Wa
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Water-resistant seal Chilled water
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If the active length (a) of the sen
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Sensors mounted without immersion p
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Temperature Probe sensors · Air En
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The ambient temperature at the devi
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Temperature Averaging sensors Allow
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Do not bend the capillary too tight
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When installing on "drawer"-type un
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Use spacing clips to maintain a 50
Page 33 and 34: Do not install on external walls. A
Page 35 and 36: Temperature Outdoor sensors The sys
Page 37 and 38: Seal gaps between cable/plastic tub
Page 39 and 40: Temperature Surface-mounted strap-o
Page 41 and 42: Temperature Wind sensors Install on
Page 43 and 44: Avoid shade (from trees or neighbou
Page 45 and 46: A test hole must be provided for ev
Page 47 and 48: Distance for adiabatic humidificati
Page 49 and 50: Humidity sensor Average humidity me
Page 51 and 52: Seal gaps between cable/plastic tub
Page 53 and 54: Where there is a risk of condensati
Page 55 and 56: Avoid using tips which protrude int
Page 57 and 58: Where more than one sensor is used,
Page 59 and 60: Pressure Liquids Pressure tapping p
Page 61 and 62: Pressure measurement in conjunction
Page 63 and 64: Flow monitoring Water Correct insta
Page 65 and 66: Avoid recesses (e.g. shelving) and
Page 67 and 68: Floats: These are used in open and
Page 69 and 70: Principles of operation General All
Page 71 and 72: Example of response characteristic
Page 73 and 74: Stepless devices Stepless devices (
Page 75 and 76: Bimetal rod and tube Material Const
Page 77 and 78: Electrical resistance sensors Metal
Page 79 and 80: Thermocouples These consist of two
Page 81 and 82: Absolute humidity x g H 2O per kg o
Page 83: Electronic systems Piezoelectric el
Page 87 and 88: Room temperature measurement Room s
Page 89 and 90: Calibration of measuring sensors Th
Page 91 and 92: Practical tips Frost protection the
Page 93 and 94: Preventive frost protection thermos
Page 95 and 96: Pressure control in VAV systems The
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Sensor Installation Handbook Preface 3rd edition - Siemens ...

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