Tuesday, May 17, 2016

Magnetostrictive Level Transmitter for Process Measurement & Control

Magnetostrictive liquid level transmitter for industrial process measurement and control
Liquid Level
Physical properties of certain materials can be applied using ingenuity and creativity to create useful appliances. Magnetostriction, a physical property of ferromagnetic materials, produces a change in shape or dimension in the subject material when it is magnetized. This basic principle is integrated into a liquid level transmitter by extending a sensing wire along the interior length of a tube immersed in a process tank or other vessel containing the liquid to be measured. The transmitter pulses the sensing wire with an electrical current, creating an electromagnetic field. A magnetic float, travelling along the outside of the sensing tube, rises and falls as the liquid level in the tank changes. As the float moves along the length of the sensing tube, it creates a torsional stress in the sensing wire, starting at the position of the float, which matches the level of liquid in the tank. A sensing element converts the torsional stress in the wire to an electrical pulse. The transmitter measures the time differential between the initial pulse it sent down the sensor wire and the pulse resulting from the torsional stress and then calculates the position of the float and the liquid level.

These devices are very accurate and operate on a standard 2-wire loop. There are numerous options and variants that allow configuration for each application.

More information is included in the data sheet below. Your best source for current product and application information is a product specialist. Combining your process knowledge with their application expertise will produce the best outcomes.

Wednesday, May 11, 2016

Temperature Sensors for Process Measurement - Thermocouple, RTD, Thermistor

straight tube thermocouple, RTD or thermistor for temperature measurement
Simple RTD, thermocouple, thermistor
straight tube assembly
Courtesy Smart Sensors, Inc.
This post explains the basic operation of the three most common temperature sensing elements - thermocouples, RTD's and thermistors.

A thermocouple is a temperature sensor producing a micro-voltage from a phenomena called the Seebeck Effect. In simple terms, when the junction of two different (dissimilar) metals varies in temperature from a second junction (called the reference junction), a voltage is produced. When the reference junction temperature is known and constant, the voltage produced by the sensing junction can be measured and a corresponding temperature derived.

Thermocouples are widely used for industrial and commercial temperate control because they are inexpensive, exhibit appropriate accuracy for many applications, have a fairly linear temperature-to-voltage output curve, come in many “types” (different metal alloys) for many different temperature ranges, and are easily interchangeable. They require no external power to work and can be used in continuous temperature measurement applications from -185 Deg. Celsius (Type T) up to 1700 Deg. Celsius (Type B).

Common application for thermocouples are industrial processes, the plastics industry, kilns, boilers, steel making, power generation, gas turbine exhaust and diesel engines, They also have many consumer uses such as temperature sensors in thermostats and flame sensors, and for consumer cooking and heating equipment.
wire wound RTD
Coil wound RTD element
(image courtesy of Wikipedia)

RTD’s (resistance temperature detectors), are temperature sensors that produce a measurable change in resistance as the temperature of the RTD sensing element changes. They are normally designed as a fine wire coiled around a bobbin (made of glass or ceramic), and inserted into a protective sheath. They can also be manufactured as a thin-film element with the pure metal deposited on a ceramic base much like a circuit board.

thin film rtd
Thin-film RTD element
(image courtesy of Wikipedia)
The RTD wire is usually a pure metal such as platinum, nickel or copper because these metals have a predictable change in resistance as their temperature changes. RTDs offer considerably higher accuracy and repeatability than thermocouples and can be used up to 600 Deg. Celsius. They are most often used in biomedical applications, semiconductor processing and industrial applications where higher accuracy is important. Because they are made of pure metals, they tend to more costly than thermocouples. RTDs do need to be supplied an excitation voltage from the control circuitry.

The third most common temperature sensor is the thermistor. Thermistors work in a similar fashion to RTDs, in that they are a resistance based device, but instead of using pure metal, thermistors use a very inexpensive polymer or ceramic material as the element. The practical application difference between thermistors and RTD’s is the resistance response curve of thermistors. It is very non-linear, making thermistors useful over a narrower temperature range than RTDs.

Thermistor bead with wires
(image courtesy of Wikipedia)
Thermistors however are very inexpensive and have a very fast response. They also come in two varieties, positive temperature coefficient (PTC - resistance increases with increasing temperature), and negative temperature coefficient (NTC - resistance decreases with increasing temperature). Thermistors are used widely in monitoring temperature of circuit boards, digital thermostats, food processing, and consumer appliances.

Temperature sensors are available in an almost infinite number of assemblies and configurations to accommodate every conceivable application. Share your application with a product specialist and take advantage of their application knowledge and experience.

Friday, May 6, 2016

New Generation of Mettler Toledo M300 pH/ORP, Dissolved Oxygen, Conductivity, & Ozone Transmitters

M300 Process
M300 Process Transmitter
METTLER TOLEDO Process Analytics has released a second generation of M300 transmitters for pH, Conductivity, Oxygen, and Ozone sensors in April 2016. This release simplifies both the Process and Water M300 portfolio through the reduction of 26 unique model numbers down to ten. This is possible through new mix-mode functionality providing compatibility of both analog and digital Intelligent Sensors Management (ISM®) sensors to the latest generation. New M300 transmitters are easily identified by their high-contrast touchscreen display and advanced ISM diagnostic capabilities providing significant advantages to the product line.

The multi-parameter M300Process transmitter line for pH/ORP, dissolved oxygen, conductivity and ozone measurements offers exceptional measurement performance as well as excellent user ergonomics.

The high contrast black and white touchscreen together with the harmonized menu structure for all parameters, facilitates navigation and ensures easy and user friendly operation.

On-line diagnostics information allows you to schedule sensor maintenance or replacement. The clearly visible diagnostic information lets you know when it’s time to do maintenance or calibration of sensors equipped with Intelligent Sensor Management (ISM) technology.

The integrated USB interface allows you to use it for data logging or to store the configuration on a USB stick.

Second generation M300 transmitters are direct replacements to first generation products.

For more information, contact:
Alliance Technical Sales
312 Park Avenue Unit 145
Clarendon Hills, 60514-0145
Phone: 630-321-9646
Fax: 630-321-9647

Tuesday, May 3, 2016

Safeguarding CO2 Measurements: How Intelligent and Automatic Sensor Protection Increases Performance

Instrumentation uptime and accurate measurement values are core requirements of in-line dissolved CO2 measurement systems used in carbonated soft drink facilities, breweries and boutique beverage producers. The stability and protection of the wetted sensor along with the instrument air supply are core requirements to ensure reliable measurement data. Instrument damage, incorrect CO2 readings, and poor quality can result from an unknown or undetected failure of the sensor.

The following paper, courtesy of Mettler Toledo Ingold explains how intelligent and automatic sensor protection increases reliability, quality and performance.

For more information on CO2 measurement, contact:
Alliance Technical Sales, Inc.
312 Park Avenue Unit 145,
Clarendon Hills, 60514-0145
Phone: 630-321-9646
Fax: 630-321-9647

Sunday, May 1, 2016

Welcome to the Alliance Technical Sales Blog

This site is intended to provide interesting and helpful information about process control systems and control instrumentation.

We will be contributing weekly posts of information regarding process analyzers, measurement & control, fundamentals of process control, and will present interesting applications.

We hope up enjoy this site and make it a habit to check back each week.