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

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Pressure 74 Measuring pressure Force/deflection systems With pressure sensors of this type the pressure is converted into a change in position or force. This can be used to: ■ Move a pointer ■ Operate a switch ■ Adjust a potentiometer, etc. There are various ways of converting the pressure into a deflection. The main methods are: ■ Bellows: Pressure switches or manostats for higher pressures ■ Bourdon tube: Manometers ■ Diaphragm: Fine-pressure measuring instruments ■ Aneroid barometer: Fine-pressure measuring instruments Bellows Bourdon tube Diaphragm Barometer
Electronic systems Piezoelectric elements: The force acting on the quartz crystals generates an electrical charge. This charge is converted into an output signal corresponding to the pressure. Thermodynamic pressure sensors: The amount of air flowing through the pressure tube varies according to the differential pressure. The air is heated by a heating element with a constant heat output. The higher the differential pressure, the more air will flow through the tube, thereby reducing the heating effect. The change in temperature is measured by two sensor elements, and provides a measure of the differential pressure. Important: Take care to size the differential pressure tube correctly (see page 47). Output Quartz Quartz Heating element Pressure 75
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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
Page 27 and 28:
Do not bend the capillary too tight
Page 29 and 30:
When installing on "drawer"-type un
Page 31 and 32: 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: Absolute humidity x g H 2O per kg o
Page 85 and 86: Measuring water velocity and flow L
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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