Tuesday, June 18, 2019

The Operating Principle of Thermocouples

When two dissimilar metal wires are joined together at one end, a voltage is produced at the other end that is approximately proportional to temperature. That is to say, the junction of two different metals behaves like a temperature-sensitive battery. This form of electrical temperature sensor is called a thermocouple:



This phenomenon provides us with a simple way to electrically infer temperature: simply measure the voltage produced by the junction, and you can tell the temperature of that junction. And it would be that simple, if it were not for an unavoidable consequence of electric circuits: when we connect any kind of electrical instrument to the thermocouple wires, we inevitably produce another junction of dissimilar metals. The following schematic shows this fact, where the iron-copper junction J1 is necessarily complemented by a second iron-copper junction J2 of opposing polarity:


Junction J1 is a junction of iron and copper – two dissimilar metals – which will generate a voltage related to temperature. Note that junction J2, which is necessary for the simple fact that we must somehow connect our copper-wired voltmeter to the iron wire, is also a dissimilar-metal junction which will also generate a voltage related to temperature. Further note how the polarity of junction J2 stands opposed to the polarity of junction J1 (iron = positive ; copper = negative). A third junction (J3) also exists between wires, but it is of no consequence because it is a junction of two identical metals which does not generate a temperature-dependent voltage at all.

The presence of this second voltage-generating junction (J2) helps explain why the voltmeter registers 0 volts when the entire system is at room temperature: any voltage generated by the iron-copper junctions will be equal in magnitude and opposite in polarity, resulting in a net (series-total) voltage of zero. Only when the two junctions J1 and J2 are at different temperatures will the voltmeter register any voltage at all.

For more information about thermocouples (or any temperature sensor), contact BCE. They can be reached by calling 510-274-1990 or by visiting their web site at https://bcemfg.com.

Reprinted from "Lessons In Industrial Instrumentation" by Tony R. Kuphaldt – under the terms and conditions of the Creative Commons Attribution 4.0 International Public License.

Friday, May 31, 2019

BCE Smart Flow: for OEMs Who Need Very Precise, Uniform Heat

The SMART FLOW liquid heater is designed for applications where fast heating of liquids is required. All parts exposed to liquid flow are constructed of 304/316SS (other materials available). All units have built-in Type J or K TC with potential of added adapter for outlet flow.

The Smart Flow is often customized to suit the exact power, electrical, and mechanical requirements of the application. BCE engineers are ready to provide application assistance to design and apply the perfect Smart Flow for your needs.

Smart Flow Heaters Applications Examples:

9 KW STEAM GENERATOR

BCE Smart Flow
9.0 KW (2 Zone 4500W each) (+/-10%), 240V, 23.5" Internal Length


7.5 KW STEAM GENERATOR


BCE Smart Flow
7.5 KW (2 Zone 3750W each) (+/-10%), 240V, 31.5" Internal Length


1.75 KW LUBE OIL HEATER


BCE Smart Flow
HEATER: 1750W(+/-10%), 120V, 22-23WSI, 31.5" Internal Length
SMART FLOW HEATER
  • Wetted parts constructed of 316 stainless steel standardly. Other materials available as options.
  • Liquid flow passes over an enclosed heated body, does not contact the heating element directly.
  • Multiple threaded fittings available: NPT, SAE, BSP & VCR
  • Heater designed to provide very uniform heating.
  • Made in U.S.A.
For more information about custom electric heating elements, contact BCE by calling (510) 274-1990or by visiting https://bcemfg.com.

Tuesday, May 28, 2019

Custom Coiled Cable Immersion Heater with Thermocouple and Thermal Cutout

Custom Coiled Immersion Heater
BCE Custom Coiled Immersion Heater
with thermocouple and thermal cutout.
A major US Aerospace company approached BCE in need of a custom heating solution.  

Their existing heating element failed to evenly distribute heat inside a water reservoir, leading to thermal stratification and hotspots. 

Additionally, while the customer's existing thermal system included temperature limiting devices, the new heater design required it's own thermal cut-out to ensure over-temperature protection and remove any possibility of a runaway condition.

The coiled immersion heater needed to satisfy the following:
  • Temperature uniformity throughout the heated section (± 3 C)
  • Hermetic seal 
  • Over-temperature heater failure
  • Thermocouple for additional temperature measurement
  • 275 Watt, 115 Volt
OUTCOME

Click for larger view.
BCE designed a highly effective coiled heater with exceptional heat uniformity.  An additional
thermocouple was welded to the sheath of the heater to ensure accurate temperature measurement. A thermal cutout was placed into the NPT bushing and potted with thermally conductive epoxy to allow for heater failure if all other safety systems fail. 

BCE was able to design, create 3D models/ drawings, and provide the custom heating elements within a 3 week timeframe.

Contact BCE:
510-274-1990

Monday, May 20, 2019

BCE Mini Clean Flow: An OEM Customizable Clean Gas and Fluid Heater

Mini Clean Flow
Click on Mini Clean Flow drawing image for a larger view.

The BCE Mini Clean Flow electric heater is a very compact, fast responding electric heating element for liquids and gases used in the fuel cell, bio-med, laboratory, food, and pharmaceutical industries. Typical applications include: Parts cleaning; Critical fluid heating; Solvent replacement; Biomass extraction; Bio reclamation; Semiconductor processing equipment; and photoresist materials.
Mini Clean Flow
Click on Mini Clean Flow drawing image for a larger view.

The Mini Clean Flow is often customized to suit the exact physical, mechanical and operational requirements of the application. BCE engineers are ready to provide application assistance to design and apply the perfect Mini Clean Flow for your needs.
Mini Clean Flow
Click on Mini Clean Flow drawing image for a larger view.

These examples are just a few of the many custom configuration BCE has developed for customers.
Mini Clean Flow
Click on Mini Clean Flow drawing image for a larger view.
For more information about custom electric heating elements, contact BCE by calling (510) 274-1990 or by visiting https://bcemfg.com.

Saturday, April 20, 2019

High Amperage Electrical Feedthrough

High Amperage Electrical Feedthrough
BACKGROUND

A customer involved in lithium ion research approached BCE in need of a high amperage feedthrough that also met their packaging (size) requirements.

While the customer had no problem finding high amperage feedthroughs, or feedthroughs that met their size requirement, they could not find an acceptable electrical feedthrough that satisfied both.

BCE is known for designing to customer specifications, allowing engineers the freedom to build their systems according to their plans, and not having to make design sacrifices because of hardware limitations. This application is an excellent example of BCE's capability.

OUTCOME

After a comprehensive application review with the customer, BCE went to work. Designs were completed in a few days and prototypes were completed in a few weeks. After preliminary tests and designs, a final prototype High Amperage Feedthrough was delivered for customer evaluation.

After thorough testing, the customer agreed that the application requirement was precisely met and the feedthrough functioned perfectly.

With the feedthrough now in production, all customer specified tests are performed prior to shipping and completed at BCE. Production and testing are controlled by a jointly developed standard operating procedure (SOP).

While this feedthrough was designed for a single, specific use, the underlying construction is designed to easily accommodate changes. Nearly every feature is customizable, including conductor type and gauge, flange type and size, component materials, and electrical rating.

The BCE High Amperage Feedthrough needed to satisfy these customer criteria:
  • 150 Amp 30 Volt
  • Custom KF50 Flange 
  • Vacuum rating: 10-6 ATM-cc/s 
  • Feedthrough Seal Temp: -10 C to 60 C
  • Able to withstand the weight of the heavy gauge wire
  • ALL TESTS PERFORMED AT ROOM TEMPERATURE