Precision Temperature Sensors for the Aerospace, Satellite Communications, and Space Industries

Duro-Sense Corporation
310-533-6877
https://duro-sense.com

Thermocouples Used in The Plastics Molding and Forming Industry

The term "plastics thermocouple" refers to a thermocouple used in the plastics, packaging, and rubber industries. Plastic thermocouple installations include injection molding, thermoforming, vacuum forming, and extruding machines to precisely measure the temperature of the plastic molds and nozzles. While plastic thermocouples come in various configurations such as bayonet, washer style, shim style, nozzle, and right angle, their essential components remain the same. 

Plastic thermocouples are typically calibrated to ANSI types J or K. Thermocouples lead wire comes in a variety of insulation and protection options, including high-temperature fiberglass, PVC, stainless steel braided fiberglass, and stainless steel flexible armor cable. Bare leads, male thermocouple jacks, female thermocouple plugs, or spade lugs are the most common electrical connections. 

Bayonet designs are straight or right-angle configurations, with industry-standard bayonet fittings easily retrofitted to most injection molding and plastics processing equipment. These fittings have adjustable depth and are spring-loaded to contact the media. The thermocouple sensing junction is welded or crimped directly to the washer or shim in washer and shim thermocouples. 

Bayonet thermocouples have a tube and wire design with stranded thermocouple cable running the length of the probe, and a metallic sensor is a stainless steel from the 301, 304, or 316 series. The thermocouple has either a grounded or an ungrounded junction. While the probe has a speedy response, a grounded T/C junction welded to the probe's tip can conduct electrical noise back to the instrumentation. An ungrounded junction is isolated from the metallic sensor and prevents the transmission of electrical noise. On the other hand, Ungrounded T/C junctions are slightly slower to respond to temperature changes.

Engine, Turbine and Compressor Thermocouples

A lot of electricity is needed to run complicated equipment on offshore oil and gas installations. Some of the things that need power in the drilling and processing area are pumps, valve operators, critical communications, turntables, engines, safety devices, and more. Like that used by a small town, much electricity gets consumed. Heating, air conditioning, water desalination, food storage, and even trash processing all use electricity from electric generators that run on gas or electricity. 

The conditions on offshore sites can be challenging. Equipment and parts must be robust to work correctly and cut down on regular maintenance. 

Temperature is one of the most critical measuring factors in a compressor, and its accuracy directly impacts compressor efficiency. According to the findings, temperature calculation errors account for more than 80% of efficiency errors. More information about compressor temperature measurement, as well as improved temperature measurement methods, are needed. Thermocouples measure the temperature of the interstage gas compressor and the temperature of the exit gas. 

In these cases, a unique temperature sensor called an "engine-compressor thermocouple" is used to measure temperature. These are temperature sensors that can tell you about many things, like how hot the exhaust gases are and how hot the lubricant is. Such sensors have been used for a long time and built to withstand the extreme mechanical and climatic conditions found in offshore maritime environments. If the thermocouple has exposure to a lot of vibration and chemicals, it needs to be durable and accurate at the same time. 

Engine-compressor thermocouples give oil and gas platform workers precise measurements, high precision, and quick responses to changes in the engine's temperature and compressor. As a bonus, engine-compressor thermocouples are easily calibrated, removed, and replaced if needed.

Duro-Sense Corporation
310-533-6877
https://duro-sense.com

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Protecting Against Noise in Thermocouple Installations

Thermocouples are widely used to measure temperature because they are durable, affordable, and have a wide temperature range. A thermocouple is formed by the joining of two different metal alloys at a common point referred to as the measuring or hot junction. Thermocouple lead wires attach to a temperature measuring instrument at a second connection point called the reference or cold junction. When the hot junction is heated, the thermocouple generate a very modest DC voltage. The tiny voltage signal is detected by the temperature measuring instrument and converted to a temperature reading. 

Thermocouples produce voltages in the millivolt range, with microvolt changes per degree C temperature change.  The signal (voltage) of a standard thermocouple is low, on the order of 10 mV, and the signal-to-noise ratio can rapidly drop in the presence of the types of electrical noise seen in most industrial situations. A small amount of noise can have a significant impact on precise measurement. 

There are numerous sources of noise that can interfere with thermocouple measurements.  The three most typical sources of noise are as follows: 

Common Mode Noise from Ground Loops  

Common mode noise generates an undesirable voltage on both leads of the thermocouple. Common mode noise is typically induced by a ground loop, which occurs when a system has a potential difference between two grounds. Because the tip of a thermocouple is a bare wire junction, a ground loop might form. If the tip is grounded where it is detecting temperature and that ground is at a different potential than the ground at the thermocouple's measuring end, a ground loop forms and current flows. 

Normal Mode Noise from Electromagnetic Fields  

Normal mode noise generates a current that flows in the opposite direction as the measuring current. This form of noise is often created by massive alternating current current sources, such as power lines, which generate a magnetic field. The magnetic field, in turn, generates a current in the measurement path. Motors, lights, and power lines are examples of high-current devices. Normal mode noise is typically at 50/60 Hz line frequency. The normal mode error current is proportional to the field intensity, the size of the loop, and the loop's orientation to the field. 

Electrostatic Noise from Rotating Equipment

Stray capacitance introduces electrostatic noise into the measuring path. Electrostatic noise is created by rotating equipment, which generates an alternating current (AC) current that is capacitively connected into the measurement route. Electrostatic noise can be coupled by stray capacitance through the tip of a thermocouple. 

The following procedures will significantly reduce thermocouple susceptibility to electrical noise in an industrial setting. 

• Twist and foil shield the extension or lead wires from the thermocouple to the measurement instrument. Twisting wires together minimizes both outgoing and incoming noise caused by electromagnetic interference. Each wire in the circuit carries voltages that are both equal and diametrically opposed. The voltages on the two lines are the same, but the polarity is reversed. The polarity of the magnetic field formed around the wire is determined by the polarity of the electric voltage going through the wire. Not only is the polarity of the electric voltage on each wire opposite, but so is the polarity of the magnetic fields radiating from each wire. When equal but opposing forces collide, they cancel each other out. 
• Ground the measurement junction at the point of measurement. The grounding is typically to the inside of the stainless steel sheath that covers the actual thermocouple. The advantage of grounding the measurement junction is that the electrical noise is distributed equally on each wire of the thermocouple.
• Use a transmitter with excellent common mode voltage rejection and position it as close to the thermocouple as possible.

Duro-Sense Corporation
310-533-6877
https://duro-sense.com

Critical Electricity Generation on Offshore Oil Platforms Rely on Robust Engine-Compressor Thermocouple Design

Powering a wide range of complex equipment on offshore oil and gas installations necessitates a considerable amount of continuous electricity. Pumps, valve operators, critical communications, turntables, engines, and safety devices are just a few examples of the drilling and processing environment that require a dependable power source. A vast amount of electrical power, comparable to that of a small town, is needed. Heaters, air conditioners, water desalination, food storage, and even trash processing need electricity from electric generators. 

The circumstances on offshore sites are challenging. Equipment and components must be sturdy to perform correctly and reduce the need for routine maintenance.

Temperature is one of the most crucial measuring factors for a compressor, and its precision directly impacts compressor efficiency. According to the findings, temperature calculation errors account for more than 80% of efficiency errors. More aspects of compressor temperature measurement, as well as improved temperature measurement methods, are required. Thermocouples measure the temperature of the inter-stage gas compressor and the temperature of the exit gas. 

In these applications, a specialized temperature sensor called an 'engine-compressor thermocouple' detects temperature. These are heavy-duty temperature sensors that detect several factors, such as exhaust gases and lubricant temperatures. Such sensors have been time-tested and built to survive offshore maritime environments' extreme mechanical and climatic conditions. The thermocouple must be robust enough to endure high vibration and corrosive environments while being accurate and fast responding. 

The engine-compressor thermocouple offers oil and gas platform personnel precise measurements, high precision, and quick response times. Additionally, engine-compressor thermocouples are easily calibrated, removed, and replaced if necessary.

Duro-Sense Corporation
310-533-6877
https://duro-sense.com