51. What is a Thermocouple?

The junction of two dissimilar metals which has a voltage output proportional to the difference in temperature between the hot junction and the lead wires (cold junction)

52. What is Zero Power Resistance?

The resistance of a thermistor or RTD element with no power being dissipated.

53. what is Pressure?

Pressure is the amount of force applied to a unit area; Force divided by Area = Pressure; the SI unit for pressure is the Pascal (Pa) which is derived from Kilogram per Metre Squared (kg/m2).

54. what isAbsolute Pressure?

Absolute Pressure is one which is measured relative to a perfect vacuum.

55. define Barometric Pressure

Barometric Pressure or Atmospheric Pressure is the total outside air pressure measured with reference to absolute vacuum. The pressure varies depending on geographical location, altitude and local weather conditions.

56. what is Bar?

Bar is a widely used metric unit of measure for pressure and 1 bar converts precisely to 100000 Pascals.

57. what is Bonded Foil Strain Gauges ?

Bonded Foil Strain Gauges are metal based foil elements that are incorporated into a flexible electrically insulating material which can then be bonded to a diaphragm with adhesives. As pressure is applied to the diaphragm the strain gauge will deform and its resistance will change.

58. what is Burst Pressure ?

It is a design safety limit which should not be exceeded. If this pressure is exceeded it may lead to mechanical breach and permanent loss of pressure containment.

59. what is Ceramic Pressure Sensors

typically use diaphragms made from Alumina (Al2O3) with a screen printed thick film strain gauge circuit. Ceramic diaphragms are very inert and provide a high level of protection from aggressive chemicals.

60. Compound Pressure Ranges

These are ones that combine positive and negative pressure ranges into one pressure measurement device.

61. what is Differential Pressure ?

It is the difference between two separate pressure points.

62. Digital Compensation ?

It is the process of collecting many measured points at different pressures and temperatures and using this data to correct the output of a pressure transducer so that the pressure accuracy and thermal errors can be improved beyond what is practically achieved with analogue compensation.

63. Full Range Output or FRO

It is the maximum electrical output signal for an analogue output pressure sensor.

64. Full Scale Output or FSO

It is the maximum electrical output signal for an analogue output pressure sensor.

65. Gauge Reference Pressure ?

It is a pressure measured relative to atmospheric or barometric pressure.

66. Hydrostatic Pressure ?

It is what is exerted by a liquid when it is at rest. The height of a liquid column of uniform density is directly proportional to the hydrostatic pressure.

67. what is Inch of Water Gauge or Inches of Water Column ?

It is an english and american unit for measuring liquid level. 1 inch of water column at 4 degrees celsius equals 249.089 Pascals.

68. what is Long Term Stability or Long Term Drift ?

It is the amount of change of a measured reading at exactly the same pressure and ambient conditions over a given period of time which is typically quoted as an annual figure.

69. Measurement Precision ?

It is used to describe how close together a set of results are and it means the same as non-linearity.

70. what is Negative Gauge Pressure or Suction Pressure ?

It is the difference in pressure between any vacuum pressure and atmospheric pressure.

71. what is Non-Linearity ?

It is how much a set of recorded pressures deviate from the best straight line and it is expressed as a percentage of full scale.

72. what is Overpressure or Proof Pressure ?

It is the maximum pressure that can be applied to a pressure instrument without significantly affecting its reading accuracy. Some manufacturers will state a maximum calibration shift following an over-pressure condition where others will state that the specification is unaffected.

73. what is Pressure Accuracy ?

defines the limit that any pressure measurement reading will deviate from the ideal point.

74. what is Pressure Transducer ?

It is any device that can convert a change in pressure into a varying electrical signal.

75. Pressure Transmitter ?

It is a pressure transducer which has been combined with an amplification circuit to allow the electrical signal to be sent over longer distances without degradation.

76. Primary Pressure Standard ?

These are instruments that can measure pressure very accurately by deriving a pressure reading from the fundamental components of mass, acceleration and area.

77. what is PSI, Pounds per Square Inch or Pound Force per Square Inch ?

It is a widely used British and American unit of measure for pressure.1psi converts to 6,894.76 Pascals.

78. what is Reference Pressure ?

It is the pressure present on the reverse or negative side of a sensing diaphragm. For example the pressure reading will be zero when the total pressure measured on the positive side of the diaphragm equals the reference pressure.

79. what is Secondary Pressure Standards ?

These are instruments that cannot be used to measure Force and Area directly to derive a measurement of pressure but are still used as a traceable standard for calibrating other pressure instruments, e.g. an Electronic Pressure Calibrator that uses a Pressure Transducer inside would be classed as a Secondary Pressure Standard.

80. what is Semiconductor Strain Gauges?

These are typically made from Silicon and have very high gauge factors compared to metal foil strain gauges. Ions are implanted into the n type Silicon substrate to create p type regions which are significantly more conductive than the surrounding n type Silicon. A p-n junction,created which provides electrical isolation for p-type region when reverse voltage is applied, thus creating isolated resistive region that will change with applied stress.

81. Sealed Gauge Reference Pressure ?

It is a pressure measured relative to an atmospheric or barometric pressure which has been sealed in a fixed closed volume.

82. Span Output

It is the difference between the minimum and maximum output signals of a pressure sensor.

83. Span Offset

It is the amount of deviation in maximum span output signal of a pressure sensor from the ideal value at full scale pressure. The span offset is normally expressed as percentage of full scale pressure or electrical units, e.g. ±0.5% FS or ±3mV.

84. what is Standard Atmosphere

It is a universally adopted standardized pressure reading for barometric pressure at sea level and equals precisely 1013.25mb absolute. Standard atmosphere is a particularly useful datum point in altitude measurement since all altimeters are calibrated to this pressure.

85. Static Line Pressure

It  is the total pressure present at a particular point along a pressurized pipe. It is often quoted on the specifications for differential pressure sensors as an indicator of the maximum pressure that can be applied to both the high and the low side pressure ports at the same time. This should not be confused with the over-pressure limit which is related to the differential pressure range rather than the static line pressure.

86. what is Suction Pressure or Negative Gauge Pressure ?

It is the difference in pressure between any vacuum pressure and atmospheric pressure.

87. Traceable Pressure Calibration ?

It means that the equipment which was used to calibrate a pressure measuring device has been regularly calibrated by another more accurate instrument for which its own calibration can be traced back either indirectly or directly to a National Standards Laboratory e.g. National Physical Laboratory in the UK.

88. Transducer ?

It is a device that converts a non-electrical change into an electrical change.

89. Vented Gauge Reference Pressure or VG ?

It is a pressure measured relative to “actual” atmospheric or barometric pressure.

90. Wheatstone Bridge Strain Gauge circuits ?

These are used extensively inside pressure transducers to convert mechanical stress into an electrical output signal.

91. Zero Offset ?

It is the deviation in output or reading from the ideal point at zero pressure.

92. Zero Tare ?

It is the operation of removing any Zero Offset to obtain the optimum measurement at zero pressure.

93. Factory calibration ?

The tuning or altering of a control device by the manufacturer to bring it into specification

94. Range ?

The limits within which a device or circuit operates or the distance over which a transmitter operates reliably.

95. pH ?

An indication of the acidity or alkalinity of a solution. Units range from 0 (most acidic), to 7 (neutral), to 14 (most alkaline).

96. Linearity ?

The degree to which performance or response approaches the condition of being linear. Expressed in percent.

97. Impedance ?

The opposition in an electric circuit to the flow of an alternating current. It consists of ohmic resistance, inductive reactance, and capacitive reactance.

98. what is Inch of Mercury?

It is a British and American unit of measure for pressure. 1 inch of Mercury at 0 degrees Celsius (32 deg F) equals 3386.39 Pascals.