Resources

Overview

Resources is Viatran's education center. Here you can download an application note or technical article which describes how our customers might apply our products and find out how Viatran was able to assist a particular customer with a difficult or unique application.

Here, you can learn about product specifications and benefits, read a story on how a particular customer’s business was improved by our product, deepen your technical understanding of our products’ uses and applications, or simply make sense of all the industry jargon with our handy glossary.

Check out our new Oil & Gas brochure which provides some insights into how our pressure Oil & Gas Brochure transducers are used in production, drilling, hydraulic fracturing and transportation.

It’s just one more reflection of our five plus decades of industry experience and our continuing commitment to helping our customers prosper.

Viatran’s Technical Articles/Notes are useful pieces of information that detail important points for proper use and application of our pressure transmitters/transducers.

With our Application Notes, you can learn how customers are maximizing their processes using our pressure transducers. These reports enable you to see how customers solved difficult problems and issues by using our advanced instrumentation and sensing technology.

Glossary

Absolute Pressure The pressure measured using an ideal vacuum as a zero reference point.
Accuracy The combined error due to nonlinearity, nonrepeatability, and hysteresis expressed as a percentage of full scale output.
Adaptive Tuning A self-tuning function that continuously monitors the dynamics of a process and makes adjustments to the control parameters to maintain a pre-determined setpoint.
Agency Approval Certification of conformity to the requirements of various independent testing agencies such as Underwriters Laboratories or the Canadian Standards Association.
Alarm A point in a process if the value increases above (high alarm) or decreases below (low alarm), causes an action by an indicator or controller.
Ambient Conditions The condition(s) around the transducer (pressure, temperature, etc.).
Ambient Pressure The pressure of the medium surrounding the transducer.
Ambient Temperature The average or mean temperature of the surrounding air which comes in contact with the equipment and instrument under test.
Amplifier An electronic device which boots or increases a small signal to a higher level, usually for transmission, scale convenience, or noise immunity.
Analog Output A voltage or current signal that is a continuous function of the measured parameter.
Analog Output Trim A calibration operation that allows adjustment of the output electronics to establish a value of current which conforms to a standard.
Anisotrophy The situation where properties vary according to the direction in which they are measured.
ANSI American National Standards Institute.
Apparent Shear Rate The shear rate determined in capillary viscometers without making a Rabinowitsch correction for shear thinning.
Apparent Viscosity The viscosity determined in capillary viscometry without making a Rabinowitsch correction for shear thinning.
ASCII ASCII (American Standard Code for Information Interchange) is a widely used code defined by ANSI (the American National Standards Institute). It represents the alphabet, the numeral digits, and many punctuation characters as 7-bit binary code. Packed ASCII, used in HART communications, is a 6-bit subset of ASCII which uses only upper case and omits many of the punctuation marks. It is employed so as to fit 4-bytes in a 3-byte field so that communications can be improved.
ASTM Abbreviation of American Society for Testing and Materials, an association for establishing standard testing and reporting procedures.
Auto/Manual Station The controller function that allows the operator to select the Automatic or Manual control mode. In the automatic control algorithm the controller determines the control output. In the Manual mode, the operator determines the control output.
Background Noise The total noise from all sources of interference in a measurement system independent of the presence of a data signal.
Bell 202 Bell 202 is a US telephone standard. It uses 1200 Hz and 2200 Hz as 1 and 0 respectively, a 1200 baud. Bell 202 is a full duplex communications standard using a different set of frequencies for reverse communications. HART is a half0duplex communications standard so that the reverse pair of frequencies are not used.
Bit A bit, or binary digit, which represents a single item of high/low, yes/no, or on/off information.
Breakdown Voltage Rating The AC or DC voltage, which can be applied across the insulation portion of a transducer without arcing or conduction above a specific current value.
BTU: British Thermal Unit The quantity of thermal energy required to rise one pound of water 1°F at or near its maximum density (39.1°F) (1055J).
Byte A byte is a set of bits, typically 8, which is treated as an entity. Most computers handle data bits as bytes because it is a power of two. A byte with parity is a 9 bit used for error detection.
Calibration (1)A test during which known values of pressure are applied to the transducer and corresponding output readings are recorded under specified conditions. (2)The matching of a pressure controller or indicator to the characteristics of a specific transducer. Most frequently done utilizing span resistor internal to the pressure transducer. Procedure is termed RCal. (3)Adjustment of an instrument to standards of known accuracy and stability.
Calibration Cycle Pressure calibration in both a descending and ascending mode.
Catalyst A substance that changes the rate of a chemical reaction without itself undergoing a permanent change or becoming part of the molecular composition of the product.
Checksum A checksum is an additional byte or bytes of data appended to a message group containing the arithmetic sum of all previous bytes. In HART communications, the checksum is truncated to the single least significant byte.
Coefficient of Friction A measure of the resistance to sliding of one surface in contact with another.
Cogswell's Method An approximate method for extensional viscosity measurement.
Compensation The addition of specific material or device(s) to counteract a known error.
Configuration The process of setting parameters, values and data which will determine how a transmitter will operate.
Consistency Index In the power-law viscosity model which describes the reduction of viscosity as the shear rate increases (shear thinning), m is the consistency index which is a function of temperature. This corresponds to the value of the viscosity for shear rate.
Control Output The output signal from a controller to the manipulated variable in response to input signals from the controlled variable. (See direct acting; reverse acting).
Controlled Variable A process variable which is to be controlled at some desired value by means of error; i.e. cold junction compensation for thermocouples.
Controller A device which manipulates one process variable (RPM, Heat, etc.) to result in a stable condition of a second (controlled) variable (pressure, temperature, etc).
Current Loop A two-wire loop in which the current through the wires is maintained according to a controlling device, usually a two-wire transmitter. The advantages of a current loop are longer distance signal transmission, better noise immunity, and the ability to power the two-wire transmitter throughout the same two wires. The most common current loop is 4 to 20 mA.
Cycle Time The time usually expressed in seconds for a controller to complete one on/off cycle.
Damping An analog function that modifies the response time of the transmitter to smooth the output signal in the presence of a rapidly varying input signal.
DC Direct Current.
Dead Bank The range through which input can be varied without initiating observable change in output. (There is a separate and distinct input-output relationship for increasing and decreasing signals.)
Dead Volume The volume of the pressure port of a transducer at room temperature and ambient barometric pressure.
Descriptor A sixteen character text field for additional identification information about the transmitter. The Descriptor is a user settable entry.
Differential Pressure The static pressure difference generated by the primary device when there is no difference in elevation between the upstream and downstream pressure taps.
Digital Input Auxiliary input to an indicator or controller which performs a function via switch closure or opening. Typically used to reset a latched alarm, or to duplicate a front panel function such as selection of automatic or manual control modes.
Digital Output An output signal, which represents the size of a stimulus or input in the form of a series of discrete quantities.
Digital Trim A combination trim operation which includes the separate operations of Sensor Trim and Analog Output Trim.
Direct Acting Control output action which increases as the process variable increases. In the case of an alarm, a direct acting alarm has its relay activated in an alarm condition.
Disturbance An undesired change that takes place in a process(es) that tends to affect adversely the value of a controlled variable.
Drift An undesired change in output over a period of time, of which change is not a function of the measurand.
Duplex Duplex communications means communications in both directions (as opposed to Simplex, which is communications in one direction only).
End Point The output at zero pressure and full-scale pressure.
Environmental Conditions All conditions to which a transducer may be exposed during shipping, storage, handling, and operation.
Error The difference between the value indicated by the transducer and the true value of the pressure being sensed.
Error Band The allowable deviation of output from specific reference norm.
Excitation The voltage supplied by an indicator or controller to a transducer to provide its proper operating conditions.
Fahrenheit A temperature scale defined by 32°F at the ice point and 212°F at the boiling point of water at sea level.
Failure Mode Alarm A transmitter output function that drives the analog output of the transmitter to a selectable value in the event of a failure of the electronics or sensor element. The output may be driven high, low, or assume the last valid value read by the transmitter.
Filter (Electrical) A device to sort desired result from undesired. Electrically, a selective circuit which passes through certain frequencies, while attenuating or rejecting others.
FM Approved An instrument that meets a specific set of specifications established by the Factory Mutual Research Corporation which sets industrial safety standards.
Freezing Point The temperature at which the substance goes from a liquid phase to a solid phase.
FSPR Full Scale Pressure Range. The design maximum value of input pressure that the transmitter is designed to measure.
Full Bridge A Wheatstone Bridge configuration utilizing active elements or stain gauges.
Full Scale Output The electrical output of the pressure device with full scale pressure applied. Usually expressed in electrical units (mV/V, V, mA).
Full Scale Pressure The maximum pressure under which applicable performance specifications apply.
Full Trim A sensor trim procedure in which two accurate, end-point pressures are applied to the transmitter's sensing element and all output is linearized between the values. The end-point values should be equal to or slightly outside the Lower Range Value and Upper Range Value.
Gain The ratio of the change in output to the change in input, which caused it.
Gain Adjustment Means of adjusting the full scale output of an amplified transducer.
Gauge Pressure The difference between the local absolute pressure of the fluid and the atmospheric pressure at the place of the measurement.
Ground The reference point of an electrical system, or alternatively, the local earth potential (earth ground).
Half Bridge 2 active elements or stain gauges.
HART Protocol HART, Highway Addressable Remote Transducer.
Heat Thermal energy. Heat is expressed in units of calories or Btu`s.
Hook Load The total force pulling down on the hook. This total force includes the weight of the drillstring in air, the drill collars and any ancillary equipment, reduced by any force that tends to reduce that weight. Some forces that might reduce the weight include friction along the wellbore wall (especially in deviated wells) and, importantly, buoyant forces on the drillstring caused by its immersion in drilling fluid. If the BOPs are closed, any pressure in the wellbore acting on the cross-sectional area of the drillstring in the BOPs will also exert an upward force.(Schlumberger, 2015)
Hysteresis Deviation in output within the transducer range when first approaching this point with increasing pressure and then with decreasing pressure.
Indicator A device which monitors and displays the condition of a process variable without exerting any control action. Indicators may be equipped with alarms or other auxiliary outputs.
Input and Output Resistance The resistance measured across the input (excitation) and output (signal) terminals of an unamplified transducer.
Input Fail Safe Direction in which signal is driven in the event of a sensor failure. Upscale will drive the signal fully upscale, and downscale will drive the signal fully downscale. The control output will respond as if the sensor has not failed.
Insulation Resistance The resistance measured between specified insulated portions of a transducer when a specific DC voltage is applied at room conditions.
Integral PID parameter (also called reset) which monitors and corrects the error signal between the setpoint and the process variable.
Intrinsically Safe An instrument which will not produce any spark or thermal effect, under normal or abnormal conditions, that will ignite a specified gas mixture.
ISO The International Organization for Standardization, a worldwide federation of national standards bodies from some 140 countries. Equivalent to ASTM.
ISO 9000 Family of standards concerned with "quality management". This means what the organization does to enhance customer satisfaction by meeting customer and applicable regulatory requirements.
ISOTROPY The situation where properties are independent of the direction in which they are measured.
Jumpers Wire links that allow for changes to be made in input and output hardware configurations.
K-Value of PVC A measure of the molecular weight of PVC based on measurements of viscosity of a PVC solution. It ranges usually between 35 and 80. Low K-values imply low molecular weight (which is easy to process but has inferior properties) and high K-values imply high molecular weight, (which is difficult to process, but has outstanding properties).
Kelvin (Symbol K) The units of absolute or thermodynamic temperature scale based upon the Celsius scale with 100 units between the ice point and boiling point of water. 0°C = 273.16K (there is no degree [°] symbol used with the Kelvin scale).
Linearity (End Point or Terminal) Linearity as referring to a straight line between end points.
Linearity (or Nonlinearity) The maximum deviation of the transducer output from a defined straight line during increasing pressure in a calibration cycle.
Loop Gain The product of the gains of all the elements in a loop.
Loop or Transmitter Power Supply 24 Volt DC (nominal) supplied by an indicator or controller power 2 or 4 wire transmitters.
Lower Range Limit The lowest value of the measured variable that the analog output of the transmitter is capable of measuring. Lower Range Limit, LRL, is factory set and not modifiable by the user.
Lower Range Value The lowest value of the measurand that the analog output of the transmitter is currently configured to measure. Lower Range Value, LRV, is a user settable entity.
Master The communication device which controls the operation of slave devices in a communications environment. In a Master-Slave operation, the Slave device can only respond when requested by the Master device.
Master The communication device which controls the operation of slave devices in a communications environment. In a Master-Slave operation, the Slave device can only respond when requested by the Master device.
Maximum Diaphragm Temperature The maximum temperature of the process media to which the transducer tip below the mounting threads can be exposed. Maximum strain gage temperature is the maximum environmental temperature at which the strain gage housing should be exposed.
Maximum Pressure Pressure that may be applied to a transducer without changing the transducers` performance beyond specified tolerances.
Measurand A physical quantity, property or condition which is measured. The term measurand is preferred to "input", "parameter to be measured", "physical phenomenon", "stimulus", and/or "variable.
Modem The error resultant from installing the pressure transducer, both electrical and mechanical.
Mounting Error The communication device which controls the operation of slave devices in a communications environment. In a Master-Slave operation, the Slave device can only respond when requested by the Master device.
Multidrop A mode of operation for HART transmitters. Establishes a communication system where more than two devices are connected together on a single transmission line. In such system, each device must have a unique address. The HART protocol can be operated in multidrop mode, with up to 15 slave devices on one pair of wires. The analog (4-20 mA) signals cannot be used in this mode since they would simply add together in this mode. With HART multidrop mode, each slave device assumes a fixed output current value of 4 mA.
NEMA-4 A standard from the National Electrical Manufacturers Association, which defines enclosures for indoor or outdoor use primarily to provide a degree of protection against windblown dust, rain, and/or splashing water.
Newtonian Fluids Fluids which exhibit constant viscosities independent of the shear rate. Water, glycerin, oil and other small molecule fluids are Newtonian.
Noise An unwanted signal which can contribute to errors in measurement. Examples are hum (power lines), radio frequency interference (RFI), electromagnetic interference (EMI), and broadband or white noise.
Non-Newtonian Fluids Fluids having viscosities that depend on the shear rate. Polymer solutions and melts are non-Newtonian fluids. They also exhibit other non-Newtonian properties such as stress relaxation and normal stresses.
Normally Closed The state of a switching device (relay or SSR) whose non-powered state is connected.
Normally Open The state of a switching device (relay or SSR) whose non-powered state provides no connection.
Off-Line Configuration Those procedures and data exchanges which do not have a direct impact upon the Analog Signal which the transmitter outputs or reports and which do not effect the measurement data transmitted digitally by the transmitter. They typically refer to operations which can be performed on a transmitter on a bench with the transmitter removed from a process control system.
On-Line Configuration Any operation which is performed on a transmitter which characterizes the response of the transmitter or which modifies its configuration parameters, values, or settings.
Output The electrical signal, which is produced by a pressure applied to the transducer sensor.
Parallel Parallel communications provides a multipath avenue for the transmission of several, often as many as 8 bits, bits simultaneously. Serial communications is the transmission of digital information from one device to another on a single transmission path one bit at a time. The HART protocol uses serial asynchronous communications.
Parity Parity refers to the appending of an additional bit to a byte of information for the purposes of error detection. Parity can be ODD or EVEN by agreement between the communicating parties. For ODD parity the extra bit is a 1 or a 0, so as to make the total of the ones in the byte add up to an odd number. For EVEN parity the total would add up to an even number. HART protocol appends an ODD parity bit to each byte transmitted.
PID The control algorithm providing proportional control with automatic Integral and Derivative terms. Mathematically determines the control action to be performed.
Polarity In electricity, the quality of having two oppositely charged poles, one positive and one negative.
Polling Address A unique number in the range 0 to 15 used to identify a transmitter. In multidrop operation, the allowable range of values is 1 to 15. In analog operation, the only allowable value is 0.
Positive Feedback A closed loop in which any change is reinforced until a limit is eventually reached.
Potentiometer A variable resistor often used to control a circuit.
Power Supply A separate unit or part of a circuit that supplies power to the rest of the circuit or to a system.
Pressure Range The pressure values over which a transducer is intended to measure, specified by their upper and lower limits.
Primary Loop The outer loop in a cascade system.
Proof Pressure The maximum amount of pressure that can be applied to a pressure transducer without changing any specification. See maximum pressure.
Proportional Band The PID parameter which determines the area in which the proportional control algorithm is operative.
Proportional Control (1)Current or Voltage: Control algorithm which determines a continuous linear relationship between the input and the output. (2) Time proportioning: Control algorithm that determines the time that a control output remains in the "ON" condition in a finite cycle. In this case, when the output is "ON", it is fully on.
Protocol A set of rules used in generating or receiving a message to insure reliable digital or other communications. It may involve transaction rules, message structure, coding, and physical signal characteristics.
PSIA Pounds per square inch absolute. Pressure referenced to a vacuum.
PSIG Pounds per square inch gage. Pressure referenced to ambient air pressure.
PV-Process Variable This is the controlled variable in a control situation or the monitored variable in an indicated situation.
Range The upper and lower pressure limits that a transducer is required to measure.
Rate Time The time interval over which the system variable is sampled for the derivative function.
Reference Junction The cold junction in a thermocouple circuit, which is held at a stable known temperature. The standard reference temperature is 0°C (32°F); however, other temperatures can be used.
Regrind Waste material that has been reclaimed by shredding or granulating.
Remote Setpoint An analog input to a controller which allows the setpoint to be changed by a remote device. This can be another instrument (cascading), a PLC, or computer or it can be done manually.
Repeatability The ability of a transducer to reproduce output readings when the same pressure value is applied to it consecutively, under the same conditions, and in the same direction.
Reranging A procedure allowing the modifications of configuration values and parameters that change the transmitter 4-20 mA output settings in response to input pressure readings.
Retransmission Output An analog output from an indicator or controller directly proportional to the value of the PV. Also called the recorder output.
Reverse Acting Control output that decreases as the process variable increases. In the case of an alarm, the reverse acting alarm has its relay activated in the non-alarm state. This is also called fail-safe alarm.
RFI Radio Frequency Interference.
Room Condition Ambient conditions used for test purposes.
RS-232-C RS-232-C is perhaps the most widely used standard for serial asynchronous communications. It was originally designed for interconnection of computer equipment, terminals, and modems over distances less than 50 feet. It is specified by the Electronic Industries Association, EIA. It defines the connectors, signal types, signal voltage characteristics used and provides a standard for the handshaking and control lines. Most implementations do not make use of all of the control lines or handshaking features. The RS-232-C port on most computers can be used for connection to a Bell-202 modem to provide HART communications.
Safe Overexposure The maximum pressure that can be applied to a transducer without changing its performance beyond specified tolerances.
Self Heating Internal heating of a transducer as a result of power dissipation.
Self Regulation The property of a process or machine which permits attainment of equilibrium, after a disturbance, without the intervention of a controller.
Self Tuning Generic term for algorithms from a number of manufacturers which more or less succeed in tuning the PID parameters of controllers and control systems automatically. The term is non-specific, and individual manufacturers should be consulted regarding their algorithms
Sensing Element The part of a transducer, which reacts directly in response to the pressure.
Sensitivity The ratio of the change in transducer output to a change in the value of the pressure.
Sensitivity Shift A change in the calibration slope.
Sensor Trim A digital trim procedure which permits the adjustment of a digital process variable to a precisely known input pressure. Zero Trim and Full Trim are the two Sensor Trim functions.
Serial Serial communications is the transmission of digital information from one device to another on a single transmission path one bit at a time. Parallel communications provides a multipath avenue for the transmission of several, often as many as 8 bits, bits simultaneously. The HART protocol uses a serial asynchronous communications.
Setpoint An input variable which sets the desired value of a controlled variable.
Shear Stress A tangential force divided by the area (FORCE/AREA) on which it is applied. The shear stress is equal to the viscosity multiplied by the shear rate (measured in units of pressure, i.e., MPa or psi). At the die lips under usual production conditions, the shear stress may reach values of 0.2 MPa (29.0 psi) or more. The usually accepted value for the onset of sharkskin in capillaries is 0.14 MPa (20.3 psi), although higher values are reported in industrial production. With additives the critical shear stress value might be pushed up to 0.5 MPa (72.5 psi).
Shear Viscosity The ordinary viscosity that is the ratio of shear stress to the shear rate (see also VISCOSITY).
Shield A protective enclosure surrounding a circuit or cable which is to protect it from an electrical disturbance such as noise.
Shunt Calibration/Rcal A method of generating an electrical output to match the electrical output that would be given in response to an applied pressure. This is accomplished using a resistor to unbalance the bridge electrically rather than with strain introduced by applied pressure. With standardized shunt or Rcal, the same point (generally 80%) is chosen on the calibration curve so that all similar transducers calibrate at the same point to facilitate interchangeability.
Signal Conditioner An electronic network that permits adjustments to match a particular transducer to a readout device. Generally included are provisions for adjusting for zero balance and span or sensitivity.
Signal Conditioning To process the form or mode of a signal so as to make it intelligible to, or compatible with, a given device, including such manipulation as pulse shaping, pulse clipping, digitizing, and linearizing.
Slave The communication device which is controlled by a Master device in a communications environment. In a Master-Salve operation, the Slave device can only respond when requested by the Master device.
Smart A term used to describe any instrument which is microprocessor controlled and features advanced communications capabilities.
Span The algebraic difference between the upper and lower range values.
Span Turndown The ability to re-range a transmitter to lower ranges. The re-ranging allows the 20 mA signal to be adjusted to the lower range which provides improved resolution.
Stability The ability of a transducer to retain its performance characteristics for a period of time and under a variety of conditions.
Static Calibration A calibration recording pressure versus output at room temperature.
Static Error Band The error band applicable at room temperature.
Static Pressure The pressure of a fluid or gas at rest.
Strain A technical term synonymous with deformation.
Strain Gauge A measuring element for converting force, pressure, tension, etc., into an electrical signal.
Surging An instability of melt pressure and flow rate in an extruder, which can be detected by a pressure gage at the tip of the screw (or at the die adapter), or by dimensional product variations.
Tag An 8 character text field used to identify a transmitter. The Tag is stored in the transmitter and is capable of being user modified.
Temperature Effect on Span The percentage change in rated output per degree change in ambient temperature.
Temperature Effect on Zero The percentage change in zero balance due to a change in ambient temperature.
Temperature Range, Compensated The range of ambient temperature for which Thermal Zero Shift is applicable (temperature error). Operation outside this range may require re-calibration.
Temperature Range, Operable The range of ambient temperature, given by their extremes, within which the transducer is intended to operate.
Temperature Range, Storage The range of ambient temperatures, given by their extremes, at which a transducer may be stored or transported.
Thermal Effect on Sensitivity The change in transducer full scale output due to the effects of temperature only.
Thermal Effect on Zero The change in transducer zero pressure output due to the effects of temperature only.
Thermal Mechanical Analysis In this technique, a sample is deformed under a static load as its temperature is being changed. Glass transition and softening points can be measured. The amount of orientation can also be measured by TMA.
Thermal Sensitivity Shift An instability of melt pressure and flow rate in an extruder, which can be detected by a pressure gage at the tip of the screw (or at the die adapter), or by dimensional product variations.
Thermal Zero Shift An error due to changes in ambient temperature in which the zero pressure output shifts. Thus, the entire calibration curve moves in parallel displacement.
Thermosets Materials that undergo chemical reaction and can be hardened by application of heat and pressure. They cannot be softened again to make them flowable. Typical plastics in this family are melamine, urea, epoxies and phenolics.
Transducer In the broadest sense it is a device (or medium) that converts one energy form to another. Therefore, items such as a windmill, electric light, or an automobile engine could be called a "transducer" - but, in common practice, the term is generally applied to devices that take a physical phenomenon (pressure, temperature, humidity, flow, etc.) and converts it to an electrical output.
Transmitter A device which translates the low-level output of a sensor or transducer to a higher level signal which is suitable for transmission to a site where it can be processed further.
Upper Range Limit The highest value of the measured variable that the analog output of the transmitter is capable of measuring. Upper Range Limit, URL, is factory set and not modifiable by the user.
Upper Range Value The highest value of the measurand that the analog output of the transmitter is currently configured to measure. Upper Range Value, URV, is a user settable entity.
Write Protect Mode A security feature employing password access to the transmitter's configuration values that can prevent accidental or deliberate changes to the transmitter's configuration data.
Zero Adjustment Means of adjusting the zero pressure output of an amplified transducer.
Zero Balance (Offset) The measured transducer output under room conditions with no pressure applied to the pressure port. For absolute pressure transducers, this value is measured at 0 psia. Gage and sealed pressure transducers have this value measured at atmospheric pressure.
Zero Shift Any parallel shift of the input/output curve.
Zero Trim A zero-based, one-point adjustment, typically used to compensate for mounting position effects of zero shifts caused by sensor drift with age.

Manuals