Since a negative pressure range works backwards to a positive gauge or an absolute pressure range, and that zero pressure corresponds to a full scale measurement, it has led to the use of both a forward and reverse output signal to measure suction or vacuum pressure in relation to ambient atmospheric air pressure.
Measurement & Instrumentation Guides
Guidance and reference articles for sourcing, setting up and using measurement equipment.
Totalizer
Total accumulated quantity of substance transferred.
USB
Universal Serial Bus (USB) interface computer connection
What are the advantages of using Wired Sensors instead of Wireless Sensors
This article explores the many advantages of wired sensors compared to wireless sensors in order to help you make a decision on whether to opt for a wireless sensor network over a wired sensor installation.
Digital Interface
Measurement instrumentation which can be connected via a USB, RS232 or RS485 digital interface communications.
High Frequency Response
Sensors & instrumentation that have a high frequency response measurement signal output or input.
Why use 4-20mA and 3-15 psi rather than 0-20mA & 0-15psi
Why we mainly use 4-20 mA current and 3-15 psig pressure and not use from zero to 20 mA or 15 psig?
What is the difference between zero offset and zero drift?
Zero Offset relates to the zero setting tolerance during manufacture and Zero Drift relates to the expected maximum change in zero over time.
Intrinsic Safety
A guide to intrinsic safety measurement instrumentation including explanations, applications and choice of products for installing in hazardous areas.
4 Wire
4 wire describes a sensor which has a either a wheatstone bridge strain gauge configuration or a amplified output sensor where the supply input is isolated from the signal output. 4 wire is also used to describe a resistive thermometer that is wired so that the error caused by the connecting wire on each side […]
Amplified Voltage Output
Amplified Voltage Output is convenient and robust measurement signal over medium distances to use with analogue to digital converters.
Deadband
Deadband is a region of pressure where a change in pressure produces no change in measurement output or control signal.
HART®
HART® or Highway Addressable Remote Transducer is a type of digital communications protocol for configuring and reading instrumentation via 4-20mA signal.
Piezoresistive Strain Gauges
Piezoresistive strain gauges are a semiconductor material which changes in resistance when the material stretched or compressed.
Threshold
Threshold is the amount of measurement change required before a measuring instrument reacts with a change in measurement output or produces a specified result.
Turndown Ratio
Turndown Ratio describes the difference between the highest and lowest possible span of measurement output which can be set for a sensing device with a rangeable output signal such as 4 to 20mA output which is HART enabled.
Zero Tare
Zero Tare is the operation of removing a zero offset to help obtain the optimal measurement over the whole measurement range.
Zero Offset
Zero Offset is the amount of deviation in output or reading from the exact value at the lowest point of the measurement range.
Wheatstone Bridge Strain Gauge
Wheatstone bridge strain gauge circuits are used extensively inside transducer to convert a mechanical strain into an electrical output signal.
Vented Cable
Vented Cable has a vent tube running through the inside of the cable to provide a vent path between the electrical connections at either end.
Transmitter
Transmitter (Tx) is a device which converts a sensor output into an analogue signal suitable for sending over long distances without significant signal loss or interference. A common type of sensor transmitter signal is a 4 to 20 milliamp current loop output.
Rangeable
Rangeable describes a type of measurement instrument that has an output signal which can be adjusted by the operator to a different scaling.
TSS – Thermal Span or Sensitivity Shift
Thermal Span or Sensitivity Shift signifies the maximum amount of span that will change at any measurement point within the compensated temperature range.
Span Offset
Span Offset is the amount of deviation in output or reading from the exact value at a point within the measurement span.
Square Root Extraction
Square Root Extraction is a mathematical process which is applied to a linear measurement scale to convert it to a non-linear square root scale.
Span Sensitivity
Span Sensitivity defines the output signal characteristic of a strain gauge based sensor independent of measurement range or supply voltage.
Span
Span is the difference between the lowest and the actual reading or output signal of a measurement device.
2 Wire
2 wire is used to distinguish electrical connections for measurement signals which use only two connections for carrying both the power supply and signal.
4 to 20 mA Current Loop Output Signal
4-20mA Current loop output is a type of electrical signal that is used in a series circuit to provide a robust measurement signal.
3 Wire
3 wire is used to describe a type of electrical connection for a measurement signal which has only three connections for the power supply and signal output
Transducer
Transducer is a device which measures a physical quantity such as temperature or pressure and converts it into an electrical output signal.
TSL – Terminal Straight Line
Terminal Straight Line (TSL) is a straight line drawn between the measurement output at zero and at full scale.
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.
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 […]
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 […]
Ratiometric
Ratiometric is used to describe an output signal which changes in proportion to a change input or supply voltage.
How to get a 10 volt signal from a 4-20mA output pressure sensor
I have a 4 to 20mA pressure sensor, is there a way of converting the output to a 10 volt signal so I can use a voltage input data acquisition card?
What can cause random variation in pressure transducer output
I have a 10bar pressure transducer with a 4-20mA output which is showing a random variation across a span of 0.3mA (+/- 1.5mA) at a fixed pressure.
Measurement Signal
A guide to measurement signal types for sensors & instrumentation, with explanations, applications and choice of products for analog & digital signals.
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.
Transforming a 2 wire Current Loop into a Voltage Output Signal
If you are running a signal cable over a long distance or have a spare current output pressure transmitter, it is possible to convert the output signal to a voltage type to make it compatible with voltage only input devices. A typical current output is 2 wire 4 to 20 mA which is designed to […]
What is the difference between a pressure transducer and a transmitter
When browsing through pressure measurement products you will notice that some are called pressure transducers and others are called pressure transmitters.
Supply voltage and load resistance considerations for pressure transmitters
In order for any pressure transmitter to function within designed performance levels, a min. supply voltage must be maintain device operation.