 # Glossary

## A

Absolute Pressure
Absolute pressure is the pressure measured against a perfect vacuum (zero absolute pressure).

Absolute Pressure Sensor
An absolute pressure sensor measures the applied pressure in reference to a perfect vacuum (zero absolute pressure). The specified minimum pressure (pmin) is set to absolute zero pressure (perfect vacuum)

Absolute Maximum Ratings
Absolute maximum ratings are the extreme conditions, that a product can withstand without taking damage. Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade product reliability.

Accuracy
According to EN 61298 accuracy is defined as the maximum deviation of the measurement value from the ideal characteristic curve at room temperature (RT) in % Full Span Output (%FSO). This definition includes the adjustment error (offset and span), non-linearity, pressure hysteresis and repeatability.

Amplifier
A (voltage) amplifier is a device which increases the amplitude of a voltage input signal by a certain gain, defined as the ratio of the output voltage signal to the input voltage signal. Ideally an amplifier will increase the input voltage signal's amplitude without changing any other aspects of the input signal.

Amplitude
The amplitude of a signal is defined as the deviation of a time varying signal or oscillation from its offset value.

Analog Signal
In electrical circuits analog voltage or current signals are signals of continuous in amplitude and time.

Atmospheric Pressure
Atmospheric pressure is the ambient air pressure resulting from the weight of air in earth' atmosphere in reference to perfect vacuum. Atmospheric pressure is sometimes called barometric pressure.

## B

Bandwidth
For an analog amplifier or sensor the bandwidth specifies the device's frequency behaviour. The bandwidth is the difference between the minimum and the maximum frequency, at which a signal can be processed without a decrease.

Barometric Pressure Sensor
Barometric pressure sensors are a special form of absolute pressure sensors calibrated to measure the ambient pressure against a perfect vacuum.

Best Fit Straight Line
The best fit straight line is the straight line fitted through a set of points, which minimizes the sum over the square of each points' deviation from the straight line ('least squares' method).

Bidirectional Differential Pressure Sensor
A bidirectional differential pressure sensor is a type of differential pressure sensor which is able to measure both pressure directions (the greater input pressure can be applied to either port of the pressure sensor).

Binary system
The binary system is a number system with base 2. All numbers in the binary system are represented as a string of ones and zeros. A one is represented by a non-zero voltage (high-level) and a zero by ≈ 0 V (low-level). In 4 bit binary the numbers 0, 1, 2, 3 up to 15 would be represented by 0000, 0001, 0010, 0011 .. 1111 respectively.

Bit
A bit is a single digit of a binary number.

Bridge resistance
Typically the total bridge resistance is the impedance of an uncompensated, unamplified Wheatstone bridge.

Burst pressure
Burst pressure is defined as the maximum pressure, which may be applied to one pressure port relative to the other port (or while only one pressure port is connected) without causing leaks in the sensor. The sensor should not be expected to function after exposure to any pressure beyond the burst pressure.

Byte
A byte is a 8 bit binary number.

## C

Calibration
The calibration of a sensor is the comparison with a standard and the adjustment of the sensor's output signal to bring it into alignment with the standard (according to the sensor's specifications).

Capacitance-to-Voltage Converter
A capacitance-to-voltage converter is used to convert the capacitance of a connected capacitor or capacitive measurement head into a voltage output signal.

Clipping Limits
Clipping limits are the maximum and minimum output signal limits, where the product will produce an output signal under normal operating conditions.

Common-Mode Pressure
The common mode pressure is defined as the maximum pressure, that can be applied on both pressure ports of a differential or bidirectional differential pressure sensor simultaneously without damaging the sensor housing, while no further differential pressure is applied.

Common-Mode Rejection Ratio (CMRR)
The common-mode rejection ratio of a differential amplifier is the rejection of unwanted input signals common to both inputs relative to the wanted difference signal. Typically the CMRR is expressed in dB.

Compensation
During compensation the unwanted effects in a sensor's behaviour are minimized by signal-conditioning. Typically for pressure sensors the non-linearity and temperature effects are compensated to minimize the deviation from the ideal transfer function.

Compensated Temperature Range
The compensated temperature range is the temperature range over which the sensor will produce an output signal nearly independent of temperature and following the ideal transfer function within the specified performance limits.

Corner Frequency
The corner frequency is a boundary in a system's frequency response at which the signal amplitude is decreased below a certain level. Often it is defined as the frequency where signal amplitude is reduced by 3 dB.

Current Consumption
Current consumption is the maximum current an electrical circuit will draw during operation, when no load is connected.

Current Output - Three-Wire Operation
A device with current output can be used to transmit signals over long distances. For a device with current output in three-wire operation three wires have to be used for the device's connection: one to power the system, one for the connection to ground and one for the current output. In contrast to the current output in two-wire operation the current output in three-wire operation does not depend on the device's current consumption. Therefore it is possible to generate output currents down to 0 mA.

Current-Loop Output
A device with current-loop output has a two-wire interface and a current output signal (e.g. 4 .. 20 mA). The device is connected to the power source using two wires forming the current-loop. Powered by the current-loop the device controls the current flowing in the loop. The current in the loop is the device's output signal.

## D

The dead volume is the open volume inside a product which is occupied by fluids or gases begin sensed.

Diagnostic Range
Under normal operating conditions the product will produce outputs following the transfer function. Detection of a signal outside these limits indicates a fault condition which allows the detection of a sensor failure.

Die
A die is an unpackaged silicon chip.

Differential Pressure
Differential pressure is the difference between the pressure applied at two pressure ports.

Differential Pressure Sensor
Sensor used to measure the difference between two pressures applied to the product's pressure ports.

Digital Signal
A digital signal has a discrete range of values in an electrical circuit. It is not continuous in time and amplitude. Typically the logic 1 corresponds to the high level voltage in an electrical circuit and the logic 0 corresponds to a low level voltage.

Drift
The drift of a sensor is a time dependent change of the sensor's output signal while the applied measuring and ambient conditions are constant.

Dual In-Line Package (DIP)
A Dual In-Line Package is a rectangular sensor and IC package with two parallel rows of pins usually used for through-hole assembly. Mostly DIPs are referred to as DIPn, where n is the number of the package's pins.

## E

Electrically Erasable Programmable Read Only Memory (EEPROM)
An EEPROM is a type of non-volatile electronic memory used to store data for later retrieval. It can be programmed and erased electrically.

## F

Full Span Output
The Full Span Output (FSO) is the algebraic difference between the output signal at the specified minimum input signal (e.g. pressure) and the output signal at the specified maximum input signal.

## G

Gage Pressure
Gage pressure is pressure measured relative to the local ambient (atmospheric/barometric) pressure. Also known as "gauge".

Gage Pressure Sensor
Gage pressure sensors are sensors used to measure the difference between applied pressure and local ambient (atmospheric) pressure. Typically the minimum pressure (pmin) is set to ambient pressure.

Gain-Bandwidth Product
For an amplifier the gain-bandwidth product is the product of the amplifier's bandwidth and the adjusted gain, at which the bandwidth is measured. For an operational amplifier the gain-bandwidth product is nearly independent of the gain, so that it is equal to the unity-gain bandwidth of the amplifier.

## H

The hexadecimal system is a number system with the base 16. All numbers in the hexadecimal system are represented as a string consisting of 0 .. 9 and A .. F for the numbers 0 to 15. 4 bit binary numbers can be represented using only one digit in hexadecimal numbers. In the hexadecimal system the numbers 0, 5, 10 and 15 would be represented by 0, 5, A and F respectively.

Hysteresis
Hysteresis is the output signal's dependence not only on the current input signal but also on the input signal's change direction and history. For pressure sensors temperature and pressure hysteresis are important hysteresis effects influencing the sensor's total accuracy. (see pressure and thermal hysteresis)

## I

I2C
I2C is a multi-master, multi-slave serial computer bus invented by Philips Semiconductors. The communication uses two bidirectional bus lines: a serial data line (SDA) and a serial clock line (SCL) which are pulled up using resistors. Typical voltage high levels are 5 V or 3.3 V and data rates up to 3.4 Mbit/s are allowed. Typically an I2C bus works at 100 up to 400 Hz.

Ideal Transfer Function
The ideal transfer function is the desired functional relationship between the input and the output signal of a system. For pressure sensors the ideal transfer function is a linear relationship between the applied pressure (difference) signal and the output signal with a slope equal to the Full Span Output over the desired pressure range.

Input Impedance
The electrical impedance measured across the input terminals of the product (as presented to the excitation source with the output terminals open circuited.

Instrumentation Amplifier (IA)
An instrumentation amplifier is a type of amplifier, that amplifies the difference between the input voltage signals while rejecting input signals that are common to both inputs. An instrumentation amplifier is especially suitable for use in measurement and test equipment, where high accuracy is required. It has a differential input with very high input impedance, a single-ended output with very low output impedance and internal feedback resistors isolated from the inputs. Further characteristics are a very high common-mode rejection ratio, very low DC offset, low drift and low noise.

Integrated Circuit (IC)
An integrated circuit is an electronic circuit containing all the elements of the specific circuit on a single semiconductor substrate.

## L

Line Regulation
Line Regulation is the capability to maintain a constant output voltage level despite changes in the input voltage level.

Linearity
Linearity describes the behaviour of an electrical circuit, when the transfer function is represented by a straight line. Deviations from the ideal behaviour are specified by the non-linearity. See Non-Linearity.

Load Regulation is the capability to maintain a constant output voltage or current despite changes in the connected load.

Long Term Stability
The long term stability is the maximum deviation of a system's output over time while the system is measured under the same conditions. Typically a sensor's long term stability is given in %FSO per year.

## M

Maximum Power Consumption
The maximum electrical power consumed in normal operation of an electrical system.

Media Compatibility
For pressure sensors media compatibility specifies the media which can be applied to the sensor's ports without causing damages or leaks during the sensor's specified lifetime.

Microcontroller (µC)
A microcontroller is a single purpose processing unit designed to execute small control programs often in real time. Mostly the program is stored in a non-volatile memory integrated in the microcontroller.

## N

Non-Linearity
An electrical system's non-Linearity is the deviation from a linear transfer function. It is defined as the output signal's measured deviation from a straight line fitted to the output data across the entire input range.

Non-volatile Memory
A non-volatile memory is a data storage, that maintains its stored data even, if the power is removed

## O

OEM Sensor
Our OEM sensors are parts which are designed for the installation in packages or systems and which can't be used as stand-alone product.

Offset
The offset is a constant part of a system's output signal and is independent of changes in the system's input.

Open-Loop Gain
The open-loop gain of an amplifier is the gain obtained, when no feedback is used in the circuit. Typically the open loop gain of an operational amplifier is > 105 and decreases with increasing input signal frequency.

Operating Temperature Range
The operating temperature range is the ambient temperature range over which the product can be used (and powered).

Operational Amplifier (OP)
An operational amplifier is a DC coupled, high gain, electronic voltage amplifier with differential input and usually single-ended output. It has a very high open-loop gain. Typically OPs are used in a closed loop with negative feedback, as well as resistors to adjust the circuits overall gain.

Output Impedance
The electrical impedance measured across two differential output terminals of the product or between the output terminal and GND (as represented to an external circuit).

Output Resolution
The smallest meaningful change in output signal, which can be related to an input signal change and distinguished from noise. The output resolution is usually expressed in %FSO.

## P

Piezoresistive Element
A piezoresistive element is a resistive element that changes its resistance relative to the applied mechanical stress (e.g. applied pressure).

Position Sensitivity
For a pressure sensor the position sensitivity is defined as the maximum change in the product's output due to a change in position or orientation relative to the Earth's gravitational field, when no pressure difference is applied at the membrane of the sensing element (zero pressure offset).

Power Supply Rejection Ratio (PSRR)
The power supply rejection ratio of an electrical system is defined as the ratio of the supply voltage change to the output voltage change it produces. The PSRR is usually given in dB.

Pressure Hysteresis
Pressure hysteresis is the maximum deviation of a pressure sensor's output value at any pressure within the specified range when the pressure is cycled to and from the minimum or maximum rated pressure.

Pressure Non-Linearity
The maximum deviation of a pressure sensor's output from a straight line fitted to the output measured over the specified pressure range. The standard method of straight line fit specified for this calculation is the best fit straight line.

Pressure Sensing Element
The pressure sensing element is the part of a pressure sensor, that converts the applied physical pressure into an electrical signal using a flexible membrane structure.

Pressure Transmitter
Our pressure transmitters are ready-to-use pressure sensors. They are already housed in a robust package with pressure ports and a plug or cable for electrical connection.

## Q

Quad flat no-leads packages are packages for integrated circuits with an outline close to die scale and without leads. They are used to connect integrated circuits to PCBs in surface-mount technology. Furthermore QFN packages have a thermal pad to improve the heat transfer out of the IC

Quiescent Current
Quiescent current is the current consumed by an electrical circuit when no load is connected.

## R

Ratiometric Voltage Output
The ratiometric voltage output is a kind of system's voltage output, for which the output voltage is proportional to the system's supply voltage (for any input signal within the specified range). The typical range of a ratiometric voltage output is 0.5 .. 4.5 V.

Ratiometricity Error
For ratiometric systems the output voltage is a proportion of the supply voltage, while keeping the input signal constant. The ratiometricity error is given by the maximum deviation of the output voltage signal from the ideal ratiometric behaviour due to any change of the supply voltage at any input signal within the specified range. Usually the value is specified in in ppm (normalized to the supply voltage), sometimes in %FSO.

Reference Pressure
Reference pressure is the pressure used as reference (zero). Typically this is perfect vacuum for absolute pressure sensors and local ambient pressure for gage / relative pressure sensors. In principle, no specific reference pressure is necessary for differential and bidirectional differential pressure sensors. Nevertheless the common-mode pressure limits the pressures applied to the sensor's ports relative to ambient pressure.

Room Temperature (RT)
The temperature used in the product performance measurement, typically 25 ± 3°C.

Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)
REACH is a European regulation addressing the production and use of chemical substances and their potential impacts on both human health and the environment. Its goal is to ensure chemicals of very high concern are phased out and replaced with suitable safer alternatives.

Repeatability
A pressure sensor's repeatability is the output's maximum deviation at any pressure in the specified pressure range, when the same pressure is applied consecutively, under the same operating conditions with pressure approaching from the same direction within ten pressure cycles.

Response Time
The response time is the time taken by a sensor to respond to an input signal step by changing the output value from its previous stable state to a new steady state. Usually the response time is defined as the time it takes for the sensor to traverse between 10% and 90% of its final value.

Restriction of Hazardous Substances Directive (RoHS)
RoHS restricts the use of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ether (PBDE) in the manufacture of various types of electronic and electrical equipment. The maximum permitted concentrations in non-exempt products are 0.1 % or 1000 ppm (except for cadmium, which is limited to 0.01 % or 100 ppm) by weight.

## S

Self Heating
Self heating is an electrical component's internal heating as a result of power dissipation.

Sensitivity
A pressure sensor's sensitivity is the ratio of output signal change to the corresponding input pressure change. Sensitivity is given by the ratio of full scale span to the specified difference of maximum and minimum pressure. Sometimes sensitivity is normalized using the supply voltage.

Shrink Small Outline Package (SSOP)
Shrink small outline packages are small leaded IC packages used to mount integrated circuits on PCB boards in surface-mount technology. SSOP packages have a higher pin density than SO packages.

Sink Current
The maximum current an amplified circuit can accept ('sink') on its output pin and still remain within the specified performance limits.

Slew Rate
In electronics slew rate is defined as the output voltage's maximum change rate per second. If the slew rate is too slow it can lead to non-linear effects in an amplifier's output.

Small Outline Package (SOP)
Small outline packages are small leaded IC packages used to mount integrated circuits on PCB boards in surface-mount technology.

Source Current
The maximum current an amplified circuit can supply ('source') on its output pin and still remain within the specified performance limits.

Span Error
The span error is the measured full span output's maximum deviation at room temperature relative to the ideal full span output as determined from the ideal transfer function. See also the temperature coefficient of span.

Specified Maximum Pressure (pmax)
The upper limit of a pressure sensor's specified pressure range.

Specified Minimum Pressure (pmin)
The lower limit of a pressure sensor's specified pressure range.

Specified Pressure Range
The specified pressure range is the pressure interval given by the specified minimum pressure (LL) and maximum pressure (UL). Within the specified range the product will produce an output corresponding to the ideal transfer function within the specified performance limits.

Storage Temperature Range
Storage temperature is the temperature range to which the product may safely be exposed without excitation or pressure applied. Under these conditions the product will remain in specification after excursion to any temperatures within this range. Exposure to temperatures outside this range may cause permanent damage to the product.

Supply Voltage Range
The supply voltage range is the specified range of voltage excitation which can be supplied to the product.

Supply Voltage Ratiometric Limits
The supply voltage ratiometric limits define the supply voltage range for which the product remains within the specified Ratiometricity Error.

## T

Temperature Coefficient of Offset (TCO)
The temperature coefficient of offset is the relative change of a system's offset induced by a change of the ambient temperature in reference to room temperature. For sensors the value is often given in %FSO/°C.

Temperature Coefficient of Resistance (TCR)
The temperature coefficient of resistance is the relative change of the resistor's value induced by changing the ambient temperature in reference to room temperature. Typically for sensor Wheatstone bridges the value is given in ppm/°C.

Temperature Coefficient of Span (TCS)
The temperature coefficient of the span is the relative change of span value induced by changing the ambient temperature relative to room temperature. Typically for sensors the value is given in %FSO/°C.

Temperature Compensation
A temperature compensation is the correction of unwanted thermal effects on a sensor or electrical system by signal-conditioning. For silicon pressure sensors a temperature compensation is essential to achieve an output nearly independent of temperature. See compensated temperature range and compensation.

Thermal Hysteresis
Thermal hysteresis is the maximum deviation of the output value at any temperature within the specified range when the temperature is cycled to and from the minimum or maximum specified temperature. Typically for sensors the value is given in %FSO.

Total Error Band (TEB)
For a sensor the TEB is defined as the measurement value's maximum deviation from the ideal transfer function over the entire compensated temperature range. For a pressure sensor it includes: Offset, Full Span Output, Pressure Non-Linearity, Pressure Hysteresis, Repeatability, Thermal Effects and Thermal Hysteresis.

## V

Vacuum
Vacuum is a pressure lower than atmospheric pressure (a perfect vacuum is the absence of any gases or fluids)

Voltage Reference
A voltage reference is an electronic circuit, which produces a high stable, constant output voltage (sometimes adjustable). Variations of the component's temperature, the supply voltage or the applied load within the specified ranges have no influence on the output voltage.

Voltage-to-Current Converter
A voltage-to-current converter is used to convert a voltage input signal into a current output signal. Different models for differential or single-ended input voltages as well as current output for two-wire current-loop or three-wire applications are common.

## W

Wetted Materials
Materials used in a pressure sensor which may come into direct contact with measured fluids (media) applied to the pressure ports.

## Z

Zero Pressure Offset
For a pressure sensor, zero pressure offset is the output signal measured when zero reference pressure is applied. For absolute pressure sensors zero pressure offset is measured while connecting vacuum, for barometric pressure sensors it is measured at the specified minimum pressure and for differential and bidirectional differential pressure sensors it is measured when zero pressure difference and zero common-mode pressure are applied.

Zero Pressure Offset Error
The measured zero pressure offset's maximum deviation at reference temperature relative to the ideal zero pressure offset as determined from the ideal transfer function.