Absolute Maximum Ratings
The extreme limits that a product can withstand without damage to the product. Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may de-grade product reliability
Absolute Pressure
A measure relative to perfect vacuum or zero pressure reference.
Absolute Pressure Sensor
Product whose output is proportional to the difference between the pressure applied in relation to relative zero pressure (a total vacuum on one side of the diaphragm) reference.
Accuracy
The maximum deviation of the actual output signal of a device to the true value of the input pressure measured over the compensated pressure range at reference temperature. The various errors such as (linearity, hysteresis, repeatability and temperature shift) attributing to the accuracy of a device are usually expressed as a % of span.
Analog Output
An electrical output from a transducer that changes proportionately, with any change in input pressure.
Atmospheric Pressure
The total outside air pressure measured with reference to absolute vacuum. The pressure varies depending on geographical location, altitude and local weather conditions.
Auto Zero
Typically, a zero pressure reference such as atmospheric pressure (or equal pressures on both pressure ports for a differential product) is employed to allow the external correction of Offset Error. Usually done by using a microprocessor to open a solenoid valve at a predetermined time interval. This references atmospheric pressure to both sides of the gauge pressure transducer. The microprocessor reads the output voltage and makes the new null point. This method is used to eliminate errors due
Barometric Pressure
The total outside air pressure measured with reference to absolute vacuum. The pressure varies depending on geographical location, altitude and local weather conditions.
Barometric Pressure Transducer
An absolute pressure sensor that measures the local ambient atmospheric pressure.
Baud Rate
A Unit of measure for data transmission speed. It represents the number of signal elements (typically bits) transmitted per second. Typical baud rates are 300, 1200, 2400, 4800, 9600, 14400 & 28800
Best Fit Straight Line (BFSL)
The straight line fitted through a set of points which minimizes the sum of the square of the deviations of each of the points from the straight line (“leastsquares” method).
Bi-directional Differential Pressure Transducer
A differential pressure transducer allowing the greater input pressure to be applied to either port.
Bridge Resistance
The Input Impedance of an uncompensated, unamplified analog output product.
Burst Pressure
The maximum pressure applied to the port of the product that will rupture the sensing element or transducer case causing leakage. The product should not be expected to function after exposure to any pressure beyond the burst pressure.
Calibration
The comparison of a pressure sensor output against the output of a reference standard. ESI recommend a calibration interval of 12 months, however it is the user of the calibration item that has sole responsibility for defining the exact calibration interval to best suit the application requirements.
Calibration Curve
A graphical representation of the calibration record.
Cavitation
Process in which small bubbles are formed and implode violently. This can cause aggressive damage in pipework and fittings
Chip
A die (un-packaged semiconductor device) cut from a silicon wafer, incorporating semiconductor circuit elements such as resistors, diodes, transistors, and/or capacitors.
Clipping Limits
The maximum and minimum limits of signal that the product will output under normal operating conditions.
Common Mode Voltage
The voltage between each of the output terminals of a differential output product and electrical ground.
Compensated Temperature Range
The temperature range over which the product will produce an output proportional to pressure within the specified performance limits.
Compensation
The signal conditioning used to provide a calibrated product whose output closely matches the Ideal Transfer Function. Deviation from the Ideal Transfer Function results in errors which are described by the Total Error Band. Circuitry or materials designed to counteract known sources of error are added.
Creep
The change in a sensors output occurring with time after removal of a load which had been applied for a specific period.
Creep Recovery
The change in no-load output occurring with time after removal of a load which had been applied for a specific period.
Dead Volume
The open volume inside the product which is occupied by fluids being sensed. Does not include the flow channel for flow-through pressure products.
Density
The mass of a given substance per unit volume, often expressed as g/cm3 or lbs/ft3
Differential Pressure
The difference in pressure between two independent pressure sources, measured relative to a reference pressure.
Differential Pressure Transducer
Product whose output is proportional to the difference between pressure applied to each of the pressure ports.
Direct Current (DC)
A current with constant polarity
Drift
An undesired change in output over a period of time that is not a function of any input pressure change.
End Point Linearity
see Terminal Based Linearity (TBL).
End Points
pressure transducer outputs at specified upper and lower limits of the transducer range.
Error
The algebraic difference between the indicated value and the true value of the input pressure. Usually expressed in percent of full span output, sometimes expressed in percent of the transducer output reading.
Error Band
The band of maximum deviations of the output values from a specified reference line or curve due to those causes attributable to the transducer. Usually expressed as ± percent of span output. The error band should be specified as applicable over at least two calibration cycles so as to include repeatability and verified accordingly.
Excitation
The external electrical voltage and/or current applied to a transducer for its proper operation (often referred to as the supply current or voltage).
Flow
is the motion of a fluid. A fluid can be actual liquid, gases, or movable solids (i.e., granular or slurries).
Flow Rate
The time rate of motion of a fluid expressed as a fluid quantity per unit time.
Flow Velocity
The time rate of motion of a fluid; expressed as a distance of fluid travel per unit time.
Frequency Output
An output in the form of frequency that varies as a function of the applied pressure.
Frequency, Natural
The frequency of free (not forced) oscillations of the sensing element of a fully assembled transducer.
Full-Scale Output (FOS)
The output at full-scale pressure at a specified supply voltage. The signal is the sum of the offset signal plus the full-scale span.
Full-Scale Span
The change in output over the operating pressure range at a specified supply voltage. The SPAN of a device is the output voltage variation given between zero differential pressure and any given pressure. FULL-SCALE SPAN is the output variation between zero differential pressure and the maximum recommended operating pressure.
Gauge Pressure
A form of differential pressure measurement in which atmospheric pressure is used as a reference.
Head Pressure
The height of a liquid column at the base of which a given pressure would be developed.
Hysteresis
The maximum difference between pressure sensor output readings for the same applied load; one reading obtained by increasing the measurement from zero and the other by decreasing the measurement from rated capacity.
Ideal Transfer Function
Mathematically, the Ideal Transfer Function is a straight line, which is independent of temperature, passing through the ideal Offset with a slope equal to the ideal Full Scale Span over the Operating Pressure Range.
Impact Pressure
The pressure in a moving fluid exerted parallel to the direction of the flow due to the flow velocity.
Impedance
The opposition in an electric circuit to the flow of an alternating current. It consists of ohmic resistance and capacitive resisitance.
Input Impedance (resistance)
The impedance (resistance) measured between the positive and the negative (ground) input terminals at a specified frequency with the output terminals open.
Laser Trimming
A method for adjusting the value of thick film resistors using a computer-controlled laser system.
Leakage Rate
The maximum rate at which a fluid is permitted or determined to leak through a seal. The type of fluid, the differential pressure across the seal, the direction of leakage, and the location of the seal must be specified.
Line Pressure
The maximum allowable pressure safely applied to a transducer. Line pressure is also the maximum reference pressure allowable on a differential pressure transducer.
Linearity (linearity error)
The deviation of the transducer output curve from a specified straight line. Linearity error is usually expressed as a % of span output.
Load Impedance
The impedance presented to the output terminals of a transducer by the associated external circuitry.
Long Term Stability or Long Term Drift
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.
Mass Flow Rate
flow rate expressed as fluid mass per unit time.
Maximum Common Mode Pressure
The maximum pressure that can be applied simultaneously to both ports of a Differential Pressure Sensor without causing changes in specified performance.
Maximum Excitation
The maximum value of supply voltage or current that can be applied to the transducer at room conditions without causing damage or performance degradation beyond specified tolerances.
Maximum Operating Pressure (Pmax.)
The upper limit of the Operating Pressure Range.
Maximum Power Consumption
The maximum electrical power consumed in normal operation of the product, dependent upon the Supply Voltage and any internal power saving modes of the product.
Maximum Pressure Hysteresis
The largest difference between measurements recorded during an increase in pressure from zero to full scale pressure and a decrease in pressure from full scale to zero pressure.
Measurement Precision
The limit that any pressure measurement reading will deviate from the best straight line.
Minimum Operating Pressure (Pmin.)
The lower limit of the Operating Pressure Range.
Non-Linearity
The limit that any pressure measurement readings recorded from a series of increasing pressures will deviate from the best straight line.
Null
The condition when the pressure on each side of the sensing diaphragm is equal.
Null Offset
The electrical output present when the pressure transducer is at null.
Null Temperature Shift
The change in null output value due to a change in temperature.
Offset
The output signal obtained when the Reference Pressure is applied to all available pressure ports. Also known as „null‟ or „zero‟.
Offset Error
The maximum deviation in measured Offset at Reference Temperature relative to the target Offset as determined from the Ideal Transfer Function.
Operating Pressure Range
The range of pressure between minimum and maximum pressures at which the output will meet the specified operating characteristics.
Operating Temperature Range
The range of temperature between minimum and maximum temperature at which the output will meet the specified operating characteristics.
Orientation Sensitivity
The maximum change in Offset of the product due to a change in position or orientation relative to the Earths gravitational field.'
Output Impedance
The impedance across the output terminals of a transducer presented by the transducer to the associated external circuitry.
Output Noise
The rms, peak-to-peak (as specified) AC component of transducers DC output in the absence of a change in input pressure.
Output Resolution
The smallest difference between output signal readings which can be meaningfully distinguished or resolved.
Overpressure
The maximum pressure that can be applied to a pressure instrument without significantly effecting 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.
Partial Pressure
The pressure exerted by one constituent of a mixture of gases.
Piezoresistance
A resistive element that changes resistance, relative to the applied stress it experiences (e.g. strain gauge).
Pressure
A force per unit area.
Pressure Error
The maximum difference between true pressure and the inferred from the output for any pressure I the operating pressure range.
Pressure Hysteresis
The difference in output at any given pressure in the operating pressure range when this pressure is approached from the minimum operating pressure and when approached from the maximum operating pressure at room temperature.
Pressure Non-Linearity
The maximum deviation of product output from a straight line fitted to the output measured over the specified Operating Pressure Range. Standard methods of straight line fit specified for this calculation are either BFSL or TSL.
Pressure Range
The minimum and maximum pressure that the transducer is calibrated or specified.
Pressure Response Time
Time taken for output of the product to change from 10% to 90% of Full Scale Span in response to a step change in input pressure from the specified Minimum to Maximum Operating Pressure.
Pressure Sensor
A device that converts an input pressure, into an electrical output.
Proof Pressure
The specified pressure that may be applied to the sensing element of a transducer causing a permanent change in the output characteristics.
Quiescent Supply Current
The supply current being drawn, when the pressure transducer is at null.
Range
The limits within which a device or circuit operates or the distance over which a transmitter operates reliably.
Ratiometric
ratiometricity refers to the ability of the transducer to maintain a constant sensitivity, at a constant pressure, over a range of supply voltage values.
Ratiometric (ratiometricity error)
At a given supply voltage, transducer output is a proporation of that supply voltage. Ratiometricity error is the change in this proportion resulting from any change to the supply voltage. Usually expressed as a % of full-scale output (FSO).
Reference Pressure
An independent pressure, ranging from zero pressure to some maximum pressure capability of a transducer used as a relative standard to compare the measured pressure.
Reference Supply Voltage
The voltage excitation used as a reference in measuring product performance, typically 5.00 ±0.01 Vdc.
Reference Temperature
The temperature used as a reference in measuring product performance, typically 25 ±3 °C.
Repeatability
The amount of change of a measured reading at exactly the same pressure and ambient conditions over a series of pressure cycles from zero to full scale pressure and back to zero again. To ensure no Pressure Hysteresis is introduced into Repeatability measurement, readings are always taken during an increase in pressure or a decrease in pressure but never a mixture of the two.
Resolution
The magnitude of output step changes as the pressure is continuously varied over the range. This term primarily applies to potentiometric sensors. Resolution for other pressure transducers is generally limited by sensitivity of the readout device. Usually expressed in % of full-scale output (FSO).
Response Time
The length of time required for the output of a transducer to rise to a specified % of its final output value as a result of a step change of input pressure.
Room Conditions
Ambient environmental conditions under which a transducer must commonly operate; established as follows:
(a) Temperature: 25 ± 110°C (77±18°F).
(b) Relative Humidity: 90% or less.
(c) Barometric Pressure: 26“ to 32“ Hg. Note: Tolerances closer than shown may frequently be specified for transducer calibra
Sealed Pressure Transducer
(PSIS) measures pressure with respect to an internal reference chamber sealed at atmospheric pressure. Gauge pressure measurements below 100 PSI may require corrections for changes in atmospheric pressure and thermally induced ‘reference’ pressure errors.
Self Heating
internal heating of a transducer as a result of power dissipation.
Sensing Element
That part of a transducer that responds directly to changes in input pressure.
Sensitivity
The change in output per unit change in pressure for a specified supply voltage or current.
Sensitivity Shift
A change in sensitivity resulting from an environmental change such as temperature.
Sensor
A popular term sometimes used to describe a transducer. Technically a sensor is an un-compensated, low-level output device that converts the measured to an electronic detectable change, (i.e., resistance, capacitance, and inductance).
Serial transmission
Sending one bit at a time on a single transmission wire.
Shift
An ambiguous term sometimes used to describe a permanent change in output of a sensor. The terms Offset Shift' and 'Span Shift' are also sometimes used to describe output changes due to temperature. To avoid confusion
Signal Conditioning
To process the form or mode of a signal so as to make intelligible to, or compatible with, a given device, including such manipulation as pulse shaping, pulse clipping, compensating, digitizing, and linearizing.
Sink Current
The maximum current an amplified circuit can accept („sink‟) on its output pin and still remain within the specified performance limits.
Solid State
Any element that controls current without moving parts, heated filaments or vacuum gaps.
Source Current
The maximum current an amplified circuit can supply („source‟) on its output pin and still remain within the specified performance limits.
Span
The algebraic difference between the upper and lower limits of the pressure range.
Span Error/ Span Offset
The maximum deviation in measured Full Scale Span at Reference Temperature relative to the ideal (or target) Full Scale Span as determined from the Ideal Transfer Function.
Span Sensitivity
The ratio of a change in measured output or reading to a change in pressure.
Stability
The ability of a transducer to retain its performance characteristics for a relatively long period of time, unless otherwise stated; stability is the ability of a transducer to reproduce output readings obtained during its original calibration at room conditions for a specified period of time. It is typically expressed as within % of full-scale output (FSO) for a period of “X” months.
Standard Atmosphere or ATM
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.
Static Calibration
A calibration recording output vs. pressure at fixed points at room temperature.
Static Error Band
The error band applicable at room temperature.
Static Pressure
The pressure of a fluid exerted normal to the surface along which a fluid flows. A fluid can be liquid or gaseous.
Storage Temperature Range
The range of temperature between minimum and maximum that can be applied without causing the sensor to fail to meet the specified operating characteristics.
Strain Gauge
A sensing device providing a change in electrical resistance proportional to the level of applied stress.
Supply Voltage (current)
The voltage (current) applied to the positive and negative (ground) input terminals.
Supply Voltage Operating Limits
The range of voltage excitation which can be supplied to the product to produce an output which is proportional to pressure but due to Supply Voltage Ratiometricity errors may not remain within the specified performance limits.
Supply Voltage Ratiometric Limits
The range of voltage excitation required by the product to remain within the specified performance limits for Supply Voltage Ratiometricity.
Supply Voltage Ratiometricity
The maximum deviation in ratiometric output of the product (Output divided by Supply Voltage) resulting from a voltage excitation which is different from the Reference Supply Voltage but remaining within the Supply Voltage Ratiometric Limits.
Tactile Sensing
The detection and measurement of the spatial distribution of forces perpendicular to a sensing array, and the subsequent interpretation of the spatial information. A tactile-sensing array is a co-ordinated group of Sensor Elements.
Temperature Coefficient of Full-Scale Span
The percent of change in full scale span per unit change in temperature relative to the full-scale span at a specified temperature.
Temperature Coefficient of Resistance
The percent change in the DC input impedance, per unit change in temperature relative to the DC input impedance at a specified temperature.
Temperature compensation
Correction for the influence of temperature on a measurement.
Temperature Error
The maximum change in output, at an input pressure, within the specified range resulting from a change in temperature.
Terminal Based Linearity (TBL)
or end point linearity is a method of defining linearity. The maximum deviation of any data point on a transducer output curve from a straight line drawn between the end data points on that output curve. TBL is approximately twice the magnitude of Best-Fit Straight Line (BFSL).
Thermal Coefficient of Resistance (TCR)
The deviation in Input Impedance due to changes in temperature over the specified temperature range, typically expressed as a ratio of the Input Impedance at Reference Temperature.
Thermal Coefficient of Span (TCS)
The Thermal Effect on Span expressed as an amount of Span change occurring over a specified temperature change (e.g. TCS in %FSS/25 ºC gives the amount of Span change which occurs for a 25 ºC
Thermal Coefficient Offset/ Thermal Offset Shift (TCO)
The Thermal Effect on Offset expressed as an amount of Offset change occurring over a specified temperature change (e.g. TCO in %FSS/25 ºC gives the amount of Offset change which occurs for a 25 ºC change in temperature).
Thermal Effect on Offset
The maximum deviation in Offset due to changes in temperature over the Compensated Temperature Range, relative to Offset measured at Reference Temperature.
Thermal Effect on Span
The maximum deviation in Full Scale Span due to changes in temperature over the Compensated Temperature Range, relative to Full Scale Span measured at Reference Temperature.
Thermal Hysteresis
The maximum difference between output readings when the same temperature is reached consecutively, under the same operating conditions, with temperature approaching from opposite directions within the specified temperature range.
Thick Film
Technology using screened on pastes to form conductor, resistor, thermistors, and insulator patterns; screened onto the substrate (usually ceramic) and cured by firing at elevated temperatures.
Thin Film
A technology using vacuum deposition of the conductors and dielectric materials onto a substrate (frequently silicon) to form an electrical circuit.
Tolerance
The maximum allowable deviation from a specified standard, as the range of variation permitted, expressed in actual values, or more often as a percentage of the nominal value.
Total Error Band (TEB)
The maximum deviation in output from the Ideal Transfer Function over the entire Compensated Temperature and Pressure Range. Includes all errors due to: Offset, Full Scale Span, Pressure Non-Linearity, Pressure Hysteresis, Non-Repeatability, Thermal Effect on Offset, Thermal Effect on Span and Thermal Hysteresis.
Total Flow
is the flow rate integrated over a time interval.
Total Pressure
(also called stagnation pressure or ram pressure) is the vector sum of the static pressure and impact pressure.
Transducer
A device or medium that converts energy from one form to another. The term is generally applied to devices that take physical phenomenon pressure, humidity, temperature, flow, etc., and convert it to an electrical signal.
Transfer Function
The equation which defines the output of the product as a function of pressure over the Operating Pressure and Temperature Ranges.
Transmitter
A device specifically designed to enhance communication of information from one location to another. A Pressure Transmitter is a device with a 4-20mA output specified.
Unidirectional Differential Pressure Sensor
A differential pressure transducer requiring the greater input pressure to be applied to a specific pressure port.
Vacuum
A pressure less than atmospheric pressure (a perfect vacuum is the absence of gaseous fluid).
Vibration Error
The maximum change in output of a transducer when a specific amplitude and range of frequencies are applied to a specific axis at room temperature with no pressure applied.
Vibration Error Band
The error recorded in output of a transducer when subjected to a given set of amplitudes and frequencies.
Viscosity
The resistance of a fluid to flow when subjected to shear stress.
Volumetric Flow Rate
is flow rate expressed as a fluid volume per unit time.
Wetted Materials
Materials used in the product which may come into direct contact with measured fluids (media) applied to the pressure port(s).
Working Pressure
The maximum pressure that may be applied to the product in continuous use. This pressure may be outside the Operating Pressure Range in which case the product may not provide a valid output until pressure is returned to within the Operating Pressure Range. Unless otherwise specified this applies to all available pressure ports at any temperature with the Operating Temperature Range. Note that the product may be operated continuously at pressures up to the Working Pressure, as compared with Overp
Zero
The electrical output of zero volts at null conditions.
Zero Offset
The deviation in output or reading from the ideal point at zero pressure.
Zero Pressure Offset
The output at zero pressure (absolute or differential, depending on the device type) for a specified supply voltage or current.
Zero Tare
The operation of removing any Zero Offset to obtain the optimum measurement at zero pressure.
