Glossary

A

Absolute Pressure

Pressure measured relative to a vacuum. Usually expressed in pounds per square inch absolute (psia).

Actuation Point

Also known as the trip point or set point, refers to the point of operating of the contacts at a given pressure point. Pressure point where the contacts will close on a NO switch or will open on a NC switch.

Adjustable Range

Difference between the lowest and highest adjustable actuation or de-actuation set points of a switch.

Altimetric Pressure Transducer

A barometric pressure transducer used to determine altitude from the pressure altitude profile.

Ambient Temperature

Temperature of the environment immediately surrounding a pressure sensing element.

B

Barometric Pressure Transducer

An absolute pressure transducer measuring the local ambient pressure.

Basic Output

The raw output of a pressure sensor that is neither amplified nor compensated by calibration.

Best Straight Line (BSL)

The best straight line chosen such that the true transducer response curve contains three points of equal maximum deviation.

Blood Leak Technology

Introtek offers an optical Blood Leak Detector, which will sense if Blood is leaking through a membrane and into clear Dialysate solution during a Dialysis procedure. This technology allows for threshold levels to be pre-engineered for alternate applications as well.

Burst Pressure

This specification is the maximum over pressure condition that the switch can withstand without experiencing leakage.

C

Capacitive Load

A load which the current leads the voltage

Common-Mode Error

An error that is independent of the major input variable (input pressure). For All Sensors transducers, all offset errors are common-mode errors.

Common Mode Pressure

The pressure that may be applied to both sides of the diaphragm simultaneously.

Compensated Output

Output of a pressure sensor that is compensated for one or more performance parameters such as Offset, Span, Temperature effect on Offset and Span, non-linearity, Position Sensitivity, Front to Back Linearity and Warm-up shift. Compensation of performance parameters can be achieved by design or calibration. Various compensation can be achieved by design, as an example, all A-Package products are inherently compensated for Front to Back Linearity and position sensitivity errors. Example of some parameters compensated by calibration are Offset, Span and Temperature effect on Offset and Span.

Contact Arrangement

Refers to the type of circuit or contact form for the switch. Ex: SPST, SPDT, Normally Open or Normally Closed

Contact Resistance

Electrical resistance of a pair of closed contacts.

D

Dead Band

Area from slightly above zero gauge pressure to slightly below, within which sensor travel is not sufficient to reliably actuate a mechanical switch.

De-Actuation Point

Mainly on snap acting electrical switches: the point at which the electrical switch is operated on decreasing pressure.

Design Flexibility

A variety of standard designs are available from single stand-alone systems to low cost / high volume modular designs for O.E.M. applications. Introtek can also develop custom sensors and circuitry to meet any form, fit & functional requirement.

Differential

The difference between opening (actuation) pressure and the closing (de actuation) set points.

Differential Pressure

The pressure difference measured between two pressure sources. Usually expressed in pounds per square inch differential (psid). When one source is a perfect vacuum, the pressure difference is called absolute pressure. When one source is the local ambient, the pressure is called gage pressure.

Differential Pressure Transducer

A device that measures the differential pressure between two pressure sources piped to its inputs.

Digital Output

The output of a pressure sensor that is expressed in discrete quantities (quantized), generally communicated using a standard interface such as I2C or SPI. The benefit of a digital output signal is a direct interface to a host microprocessor (uP), improved noise immunity and lower component count.

E

Electrical Contacts

The elements in the switch that electrically respond to the media applied to the actuator.

Error Band

The deviation of transducer response from its BSL, defined by lines on either side of its BSL and including the maximum deviation measured for a given normal mode or common mode error.

F

Factory Calibrated Switch

The switch is not designed for field adjustment of set points. The switch can be ordered pre configured for immediate shipment or as a standard product, tailored to user needs.

Field Adjustable

A switch that has been designed for adjustment or calibration of set points in field application.

Full-Scale

The algebraic difference between endpoints. Where one endpoint is actual offset voltage and the other endpoint is the upper limit of the range.

Full Scale Shift

The shift in sensor output voltage sensitivity to pressure over the temperature range specified. This is equivalent to temperature coefficient of sensitivity. The characteristic of this transfer curve is very close to a second order equation for the basic piezo resistive sensing element. For the millivolt output devices, this is compensated with passive resistors; and for amplified output device, it is ASIC compensated with a second order curve fit to the data taken for each part over the pressure and temperature ranges specified. The characteristic of this transfer curve does not change with any other conditions.

G

Gage Pressure

Pressure measured relative to ambient pressure (psig).

H

High Noise Immunity

Introtek’s pulse-type technology greatly reduces the potential effects of EMI, RFI and other localized stimuli, which could cause a sensor to fail.

Hysteresis of Pressure

Pressure hysteresis is measured as the maximum difference between the output at reference conditions before and after a pressure cycle.

I

Inductive Load

A load in which the voltage leads the current

Interchangeability

The error band defined by the maximum signal deviation obtained when a transducer is replaced by any other transducer of the same type with equivalent pressure inputs and temperature ranges.

L

Linearity

The maximum deviation of measured output at constant temperature (25°C) from "best straight line" determined by three points (offset pressure, full-scale pressure, and one-half full-scale pressure) where Y= measured value for each device

Linearity, Hysteresis Error

The error in the output voltage response to pressure over the full operating pressure range relative to the ideal output voltage response; the deviation from a first order transfer curve response of output signal to pressure. This error is a function of pressure and not a function of temperature. This error is computed by measuring pressure at three pressure points; zero pressure. full scale pressure and one half full scale pressure and computed on the basis of a "best straight line" curve fit to the measured data.

M

Media

Liquid or Gas the switch will be monitoring.

Motor Load

The load of a motor at rated horsepower and speed.

Minimum/Maximum

Are the guaranteed limits for the specification. These limits are generally one hundred percent tested with a guard band between the test limits and the specification limits.

Most Probable Error

The error band obtained by computing the square root of the sum of the squares of all applicable errors specified for the transducer.

N

No Calibration Required

Introtek sensors are all factory calibrated. High-efficiency system design provides optimum performance while eliminating the need for intricate or tedious field calibration.

Nominal

It is the average value for a specification from product manufactured during the first production run. Normal Mode Error: An error that is a function of (and usually assumed to be proportional to) the major input variable (input pressure). For All Sensors transducers, all span errors are normal mode errors.

Non-invasive Design

Since there is no direct contact between Introtek’s sensors and the contents of a tubing or vessel, liquid compatibility and contamination concerns are eliminated. Also, the ultrasonic signal poses no threat to the fluids, which are being monitored.

O

Offset Calibration

The error band defined by the maximum error in calibrating the offset voltage.

Offset Error

The common-mode error band defined by the maximum deviation of offset voltage from its specified value. It may include calibration, temperature, repeatability and stability errors.

Offset Long Term Drift

The change in offset voltage that may occur over the time specified. Possible causes to this characteristic for piezo resistive pressure sensors have been studied for decades. There is, to date, no conclusive single cause or main causes to the error. Because most of All Sensors low pressure sensors use dual die electrical cross coupling compensation, there is inherent offset long term drift compensation. Products All Sensors tests for warm-up shift will generally identify any offset long term drift problems and would be rejected.

Offset Position Sensitivity

The change in offset voltage due to a change in position of the sensor. Sensors for measuring pressure exceeding 15 psi have virtually no position sensitivity. Because the diaphragm of the sensor has mass, and because the mass to diaphragm thickness ratio increases as the pressure range decreases, the sensitivity to position increases as the pressure range decreases. Because most of All Sensors low pressure sensors use dual die electrical cross coupling compensation there is inherent offset position sensitivity compensation in even the most basic sensors.

Offset Repeatability

The error band expressing the ability of the transducer to reproduce the offset voltage, measured at 25°C, after exposure to any other temperature and pressure within the specified range.

Offset Stability

The error band expressing the ability of the transducer to maintain the offset voltage with constant pressure and temperature.

Offset Temperature Coefficient

The error band defined by the maximum deviation in offset voltage as the temperature is varied from 25°C to any other temperature within the specified range.

Offset Temperature Shift

The change in output offset voltage over the specified temperature range. For non amplified sensors the specification limits are tested at three temperature points; 25°C, temperature maximum, temperature minimum, and back to 25°C. For amplified pressure sensors there are many more data points measured and the compensation is mathematically fit to the data points. There is generally no consistent equation to describe the offset temperature shift characteristic. Because most of All Sensors low pressure sensors use dual die electrical cross coupling compensation there is inherent offset temperature shift compensation in even the most basic sensor.

Offset Voltage

The output voltage when the sensor has zero differential pressure across the diaphragm. For absolute pressure sensors there is zero differential pressure across the diaphragm when the sensor is at absolute pressure of zero. For gage or differential pressure sensors there is zero differential pressure when both sides of the diaphragm are subject to the same pressure.

Offset Warm-up Shift

The change in output offset voltage that may occur when power is applied to the sensor during the first hour of operation. All Sensors tests all low pressure sensors for this parameter. Because most of the companies low pressure sensors use dual die electrical cross coupling compensation there is inherent offset warm-up shift compensation in even the most basic sensors.

Operating Pressure Range

A range of inlet pressures in which the switch will operate correctly.

Operating Range

The pressure range over which the sensor has been tested. For sensors with millivolt output this range can generally be extended to at least twice the range specified with only minor degradation to specifications. For amplified output sensors the range can be extended only ten percent before the output is "railed" to the output voltage limit.

Output Span

Is the output voltage for the specified operating pressure range. For sensors without internal voltage reference the span is ratiometric to the supply voltage of the sensor. Changes in the supply voltage to the sensor with result in a change in output span for the pressure applied. The span is the difference in output voltage at full scale pressure from the offset voltage.

Over-Pressure – Maximum

The maximum normal mode (measured) pressure that can be applied without changing the transducer's performance or accuracy beyond the specified limits. This would be applied to either port of a differential transducer. This is also called "proof pressure".

Overall Accuracy – Calibrated

The combined error band relative to the BSL with forced reference unique to one specific transducer. It excludes offset and sensitivity calibration errors. It includes all other offset and span errors: temperature, repeatability, stability, linearity and hysteresis.

Overall Accuracy – Interchangeable

The combined error band relative to an ideal transducer response characteristic. It excludes stability errors because stability error is already included in specified calibration error. It includes all other offset and span errors: calibration, temperature, repeatability, linearity and hysteresis.

P

Pressure Switch Actuator

The member in the switch which receives the media and ultimately signals the electrical contacts to pen or close at the designated set point.

Pressure/Vacuum Switch

A device that senses a change in pressure/vacuum and opens or closes an electrical circuit when the point is reached.

Pressure Sensing Element

The portion of the switch that is in contact and moves as a result of change in pressure. The most common types of pressure sensing elements are diaphragms, bellows, bourdon tubes, and pistons.

Proof Pressure

The specification is the maximum over-pressure condition that the switch can have for a specified period of time and still maintain set point integrity.

Pulsed Technology

Introtek provides a patented, pulse-type ultrasonic technology for detecting air bubbles, air-in-line and liquid level detection in various fluids including Blood. Dielectric or physical properties of the tubing or fluid do not affect the functionality of the sensor.

R

Reference Pressure

The pressure used as a reference in measuring transducer errors.

Reference Temperature

The temperature used as reference in measuring transducer errors. Repeatability: The error band expressing the ability of the transducer to reproduce an output signal parameter (such as offset or span), at specified pressures and temperature, after exposure to any other pressure and temperature within the specified range.

S

Sensitivity

The ratio of output signal voltage change to the corresponding input pressure change. Sensitivity is determined by computing the ratio of span to the specified input pressure range.

Sensitivity

The threshold for sensitivity to air bubbles is pre-determined as per the customer’s specification.

Sensitivity Calibration

The error band defined by the maximum error in calibrating sensitivity.

Set Point

The pre-determined pressure/vacuum value that is required to open or close the electrical contacts in the switch.

Snap-Action Switch

A mechanically operated electric switch which, once its actuator has reached its operating (or release) point, immediately transfers to its opposite position without further travel of the actuator.

Solid State Design

With no moving parts in its design, mechanical failure is entirely eliminated.

Span

The arithmetic difference in transducer output signal measured at the specified minimum and maximum operating pressures.

Span Error

The normal mode error band defined by the maximum deviation of span from its specified value. It may include sensitivity calibration temperature, linearity, hysteresis, repeatability and stability deviations.

Span Repeatability

The error band expressing the ability of a transducer to reproduce its span, measured at 25°C, after exposure to any other pressure and temperature within the specified range.

Span Temperature Coefficient

The error band defined by the maximum deviation of the span as the temperature is varied from 25°C to any other temperature within the specified range.

Span Stability

The error band expressing the ability of the transducer to maintain the span voltage at any pressure within the specified range with temperature held constant.

SPDT- Single Pole Double Throw

The switch has three terminals, one normally open, normally closed and a common terminal.

SPST-Single Pole Single Throw

Normally Closed and a common or Normally Open and a common terminal.

Stability

The error band expressing the ability of a transducer to maintain the value of an output parameter (such as offset or span) with constant temperature and pressure inputs.

Supply Voltage

Power supply voltage applied at the input terminals of a pressure sensor. Temperature Coefficient (TC): The error band resulting from maximum deviation of a transducer output parameter (such as offset or span) as temperature is varied from 25°C to any other temperature within the specified range. It is usually measured in (ppm/°C or µV/V/°C).

Switch Contact Forms

Form A 1PST- NO Single pole, Single throw, normally open
Form B 1PST- NC Single pole, single throw, normally closed
Form C 1PDT- 1 NO/ 1 NC Sing pole, double throw, break before make
Form X 1PST-NO DB Single pole, single throw, normally open, double break
Form Y 1PST-NO-DB Single pole, single throw, normally closed, double break

Switching Element- Normally Closed

A normally closed switch conducts electricity until the actuator is moved by the media causing the contacts to open.

Switching Element- Normally Open

A normally open switch does not conduct an electrical signal until the actuator is moved by the media causing the contacts to close.

T

Temperature Compensated Output

The output of a pressure sensor that is compensated to counteract temperature dependent errors, specifically, temperature dependence of Span and Offset are compensated for. Pressure sensor output parameters are sensitive to temperature variation, specifically, pressure response (Span) and zero differential pressure output (Offset) show temperature dependency. To counteract this temperature dependency, All Sensors provides sensor products with internal circuitry that compensates for temperature variation in Span and Offset over a specified temperature range. Temperature Compensated output products are offered in Analog (non-amplified mV, amplified 4V) and digital (SPI & I2C) outputs.

Tubing Insertion Detection

Optional feature allowing for detecting that tubing is properly inserted and located within the sensor’s tubing slot.

V

Vacuum

A perfect vacuum is the absence of gaseous fluid.

Vacuum Range

The range of absolute pressures between a perfect vacuum (0 psia) and one standard atmosphere (14.697 psia).

Vacuum Transducer

A transducer scaled for pressure measurement in the vacuum range. This is usually an absolute transducer, but sometimes a gage transducer.

W

Wetted Parts

Components of a switch that are directly exposed to the media.

Worst-Case Error

The error band obtained by simple addition of all applicable errors specified for the transducer.