Instrumentation Blog

 

 
When choosing a pressure sensor for process control and monitoring in a gas flow system or a distillery component, plant operators are faced with an array of choices.

Modern pressure sensors are equipped to provide accurate measurements under arduous operating conditions, providing outstanding resistances to a range of industry-specific corrosives. Absolute, differential, and temperature-compensated pressure measurements can be acquired for containers and pipelines containing: pharmaceutical solvents; flue gas; heated crude oil; and more.

This vast range of pressure sensors represents an industrial problem of choice. The suitability of many pressure components is likely to intersect with multiple applications and sectors, yet there are unique attributes to consider when choosing a pressure sensor for your own facility.

This article will outline four key things to consider when choosing a pressure sensor.

1. Pressure Sensor Type

The primary consideration for selecting a pressure sensor is the type of component that your application requires. For example, negative pressure values cannot be quantified by a gage transmitter, while temperature-compensated pressure measurements can only be carried out by a multivariable pressure sensor or an array of separate pressure and temperature monitors. Pressure transmitters can typically be broken down into four distinct types:

  • Absolute pressure measurement sensors use full-vacuum conditions as a reference point, quantifying the pressure levels of a container as a value over 0 bar;
  • Differential pressure sensors measure the difference in applied force at two points within a flow system or a process container;
  • Gauge pressure measurement instruments use atmospheric pressure of 1.01325 bar (15 psia) as a reference point;
  • Multivariable pressure sensors measure the differential and absolute pressure, then compensate that with temperature measurements.
2. Pressure Sensor Range

The pressure range is a superficially simplistic consideration for choosing a pressure sensor. Operators typically depend upon pre-determined application pressure ranges and select a transmitter that matches those values. However, density changes or abrupt pressure variations can reduce the efficacy of measurement equipment, and in extreme cases can damage the component. In such instances, it is advisable to select a sensor with a higher pressure range and calibrate it accordingly.

3. Atmospheric / Process Conditions of Application

Prior to component selection, it is paramount that you consider the corrosive influences that your pressure sensor could be subjected to during operation. Seals may need to be wetted to withstand solvent corrosion in laboratory applications, while special considerations should be taken to protect a pressure sensor’s internal electronics. Corrosive process media or incident humidity can damage transmitters, reducing measurement accuracy and increasing the risk of premature component failure.

4. Onboarding Times

Installation of new components usually impacts a facility’s throughput due to mechanical downtime during integration and reduced efficacy from onboarding processes. For example, the pressure-sensitive diaphragms of a transmitter must be welded to measurement sites to acquire force values and convert them into electrical signals. Ease of weldability and low wiring footprints are critical for rapid and efficient component integration in applications where extended periods of component inactivity are not an option.

Pressure Sensors from ABB

ABB provides a robust range of sensors for customers all over the world. Our range has provided unique measurement solutions for facilities in the oil and gas, energy, laboratory sectors, and more.

 

 
A temperature transmitter is one of the electronic components in an industrial or laboratory thermal measurement array.

They act as the interfaces between a control system and a temperature sensor, converting analog thermal readings into scaled digital output signals with reduced background noise to enable accurate temperature monitoring with low degrees of interference. This complex system enables analysts to understand the thermal conditions of a process chamber or flow system as a value of degrees Celsius or degrees Fahrenheit in real-time.

Temperature transmitters can be manufactured as stand-alone devices that are attached to one or more temperature monitors in a process control system or integrated into a component’s connection head. The latter arrangement reduces the wiring requirements and the instrument footprint with an improved mechanical connection that is less susceptible to corrosion from process gases, vapors, or temperatures. Although the functionalities of a temperature transmitter are typically dictated by the application requirements.

Each of these component styles may be required to make signals available as an immediate digital reading and to transfer the data further down a measuring chain for additional processing. This article will explore the types, capacities, and applications of temperature transmitters in more detail:

 
Field-Mount & Head-Mount Temperature Transmitters

A field-mount temperature transmitter is an external component with an optional indicator and an encapsulating housing of die-cast aluminum or stainless steel. This protects the sensitive electronic components of the system from humidity, moisture, and other corrosive media.

Head-mounted temperature transmitters are integrated into the connection head of a temperature sensor with a direct connection to a thermowell via the extension tube and the process connection.

These are both connected with conventional Two-Wire technology, which uses the same wire connections for the power supply and signal outputs. With this technology, the temperature values are acquired by a measuring inset and converted into a thermal voltage, which is scaled into a load independent 4-20mA direct current (DC) signal. This signal can be immediately displayed on the digital indicator integrated into the transmitter’s housing, and transferred for further process control and analysis.

 
Temperature Transmitters from ABB

ABB has over 125 years’ experience in the field of temperature measurement for some of the most demanding industrial environments. Their range of temperature transmitters has been adapted for distinct application requirements, with field-mount and head-mount temperature transmitters suitable for difficult, often hazardous environments. This range includes:

  • TTH200 head-mount temperature transmitter with a universal sensor input for RTD probes and thermocouples, and an accuracy of 0.1%. This integrated devices is tested to multiple compliances for explosion protection, corrosion monitoring, and extended diagnostics.
  • TTF200 field-mount temperature transmitter with an optional LCD display and several configurable arrangements. It features the same outstanding accuracy of the TTH200 and is also tested to numerous specifications for industrial safety requirements.