Traceable Calibration is carried out using equipment that is regularly calibrated by a reference source that can be traced back to a national standard.
Definitions
Definitions for measurement terms
TZS – Thermal Zero Shift
Thermal Zero Shift (TZS) is the maximum amount the output or reading at the null measurement point might deviate over the compensated temperature range
Thermal Hysteresis
Thermal Hysteresis is the measured change in output or reading at a specific measurement point taken during a sequence of increasing and decreasing temperature.
TSL – Terminal Straight Line
Terminal Straight Line (TSL) is a straight line drawn between the measurement output at zero and at full scale.
TEB – Temperature Error Band
Temperature Error Band (TEB) is the error derived from the most positive and negative deviation of all measurement points within a measurement range over the operating or compensated temperature range.
Temperature Error
Temperature Error is the deviation of a measurement reading caused by a change in media or environmental temperature.
Temperature Compensation
Temperature Compensation is a correction applied to a measurement instrument to reduce errors attributed to temperature changes in a process media which is being measured or in the surrounding environment that the instrument is being used.
SOI – Silicon on Insulator
Silicon on Insulator (SOI) is a type of material technology which can be utilised in the manufacture of pressure sensor diaphragms to allow operation at higher temperatures.
Repeatability
Repeatability is the amount of change in a measured reading at the same measurement point after a defined number of cycles over the measurement range or a set of environmental limits.
RTE – Referred Temperature Error
Referred Temperature Error is the max deviation expressed as a +/- %FS from measurements taken at a defined temperature.
Accuracy
Accuracy of a measurement instrument defines how much a measurement value may deviate from the perfect measured value.
Precision
Precision is the measure of how closely a set of readings will be to a reference line that passes through the middle of all the points.
PVC – Polyvinyl Chloride
PVC is a widely used plastic which is cheap to produce and hard enough to be used as a component parts construction material.
PUR, PU – Polyurethane
Polyurethane is a durable polymer used for coating cables, a water tight sealing compound and a potting compound to protect electronics from damage.
FFKM – Perfluoroelastomer
Perfluoroelastomer (FFKM) is a seal material type which has a much higher temperature rating than the more common FKM and can be used on temperatures up to 300°C. FFKM also has a broader chemical resistance than FKM.
NO – Normally Open
Normally Open (NO) refers to the state of an electrical switch contact which stays open until a preset threshold has been met and the switch closes, e.g. a NO pressure switch set at 10 bar will close once the pressure exceeds 10 bar.
NC – Normally Closed
Normally Closed (NC) refers to the state of an electrical switch contact which stays closed until a preset threshold has been met and the switch opens, e.g. a NC pressure switch set at 10 bar will open once the pressure exceeds 10 bar.
NL – Non-Linearity
Non-Linearity is the deviation error derived from the straightness of a set of recorded measurements when compared to a straight line, such as bsl or tsl, drawn through all the results. The maximum non-linearity error is normally expressed as a percentage of full scale.
NPL – National Physical Laboratory
National Physical Laboratory (NPL) – national measurement institute for the United Kingdom. This organisation is responsible for maintaining the primary measurement standards for the UK.
Mechanical Stop
Mechanical Stop is an internal component which protects pressure sensing components from overpressure by limiting the deflection of the diaphragm.
MTBF – Mean Time Between Failures
MTBF or mean time between failures is a theoretically calculated value which considers all the components used in the construction of a measurement device.
MSL – Mean Sea Level
MSL or Mean Sea Level is the average height of the ocean surface. Mean sea level is a significant datum reference for meteorological and altitude related pressure measurements, e.g. standard atmospheric pressure at mean sea level is 1013.25 hPa or 29.92 inHg.
Long Term Stability/Drift
Long Term Stability or Long Term Drift 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.
LVDT – Linear Variable Differential Transformer
The Linear Variable Differential Transformer (LVDT) is a type of sensor which converts linear displacement into an variable electrical signal.
Isolation Diaphragm
An Isolation diaphragm is a thin membrane which is used to isolate the media on one side of a diaphragm from media on the other side.
IP Ratings
The IP Rating is an accepted engineering standard for defining the protection of electrical equipment from dust and moisture ingress.
Pressure Hysteresis
Pressure Hysteresis is the difference between two separate measurements taken at the same pressure but one where the pressure was increasing and the other where the pressure was decreasing. The hysteresis is caused by the natural reluctance of a pressure sensing material such as a diaphragm to return to its original position, shape or form […]
Gauge Reference Pressure
Gauge reference pressure is a pressure measured relative to atmospheric or barometric pressure. The most used pressure reference is gauge pressure which is signified by a (g) after the pressure unit (e.g. 30 psi g), and means that the pressure measured is the total pressure minus atmospheric pressure. There are two types of gauge reference […]
FSO – Full Scale Output
Full Scale Output (FSO) can have two meanings. The first meaning is that it is the resulting output signal or displayed reading produced when the maximum measurement for a given device is applied. The second meaning applies to the difference between the minimum and maximum output value. Full Range Output (FRO) and Full Span Output […]
FS – Full Scale
Full Scale (FS) is the difference between the lowest and highest possible measurement point
FKM – Fluoroelastomer
Fluoroelastomer is a fluorinated carbon based rubber material which is mostly used on pressure measurement equipment to seal joints between components which are either pressurised or water-tight.
Dry/Dry
Dry/Dry describes a differential pressure measurement device which is only compatible with dry/non-condensing gas on both the positive and negative pressure side.
Dry Cell
Pressure sensing technology which excludes any fluid filled components. The advantages of a dry cell pressure sensor are: More sensitive and responsive to measuring low pressures No risk of oil contamination if the containment isolation diaphragm fails. Compact size Lower cost of manufacture
FEP – Fluorinated Ethylene Propylene
Fluorinated Ethylene Propylene (FEP) is a resin coating that has a very high chemical and temperature resistance.
Digital Compensation
Digital compensation is the process of correcting measurement signals using look up tables or mathematical formula.
Ceramic Pressure Sensors
Ceramic pressure sensors are devices which have sensing diaphragms made from Alumina (Al2O3) with either a screen printed thick film strain gauge circuit or a variable capacitance cell. Ceramic diaphragms are very inert and provide a high level of protection from aggressive chemicals.
Cardinal Points
Cardinal points are the markings around the outside of a round analogue gauge dial which define the measurement increment divisions.
Bourdon Tube
Bourdon Tube is a flattened length of thin hollow metal tubing which is formed into a C shape.
Burst Pressure
Burst pressure 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.
Bonded Seal
Bonded seal is a metal washer with an elastomer seal bonded to its inside diameter, which is used to provide a pressure seal when placed between two flat surfaces that are screwed together using a male and female parallel thread.
BFSG – Bonded Foil Strain Gauge
Bonded foil strain gauges (BFSG) are metal based foil elements that are incorporated into a flexible electrically insulating material which can then be bonded to a surface with adhesives. As stress is applied to the material, the BFSG will deform and the resistance changes. If a voltage is applied across the BFSG it can be […]
BSL – Best Straight Line
Beast straight line (BSL) is the mathematically derived straight line which runs through the middle of a set of readings in such a way to achieve the smallest error across all the results. The measurement precision of a device is often specified in relation to the maximum deviation from the best straight line.
Compensated Temperature Range
The compensated temperature range defines the limits of operation for a specified measurement accuracy. e.g. A pressure sensor has an accuracy of 0.25% full scale over a compensated temperature range of -20 to +80 degC. Since temperature errors are often significant for many measurement devices, a manufacturer will incorporate digital or analogue temperature compensation. If the measurement device is […]
Bidirectional
Bidirectional is typically used to indicate that a particular parameter such as an electrical signal or measurement range will generate values in both the positive and the negative direction. For example a sensor which has a -10 mbar to + 10 mbar gauge pressure range with a 0 to 10 Vdc output is said to […]
Food Grade
Food grade products and substances are designed to be safe when used inside equipment and processes which are used in the production of food, pharmaceuticals and drink. Food grade products and substances prevent contaminant substances from entering the food manufacturing process which could cause physiological harm.
UKAS – The United Kingdom Accreditation Service
The United Kingdom Accreditation Service (UKAS) is a national organisation recognised by the UK government which audits and certifies calibration standard laboratories in the United Kingdom. Those who use the calibration services of a UKAS accredited laboratory are assured that the calibration will be carried out to a very high standard.
Al2O3
Al2O3 is the chemical formula for Alumina (Aluminium Oxide) which is a ceramic material that has high caustic chemical resistance and electrical insulation.
Ratiometric
Ratiometric is used to describe an output signal which changes in proportion to a change input or supply voltage.
M10 x 1
This is a metric fine thread with a outer diameter of 10 millimetres and a thread pitch of 1 millimetre.
daPa – Dekapascal Pressure Unit
Find conversions for the daPa (dekapascal) pressure unit.
mV/V – Millivolts per Volt Output Signal
It is an electrical signal which is proportional to the applied excitation voltage and is also referred to as a ratio-metric or strain gauge output.
Stainless Steel Pressure Sensors
There are many materials used for constructing pressure sensors, but those made from stainless steel are considered the most reliable and durable.