FAQ

    Why should I be interested in SVS, what can it do for me? 

If you are responsible for the performance of processes that rely on accurate temperature measurement for quality, safety, emission control, maintenance, and equipment life, the SVS will generate more bottom line revenue and make your life easier. There is an abundance of research documentation demonstrating the all thermocouples and RTDs are subject to drifting or decalibration when under thermal stress. 

The onset of decalibration is unpredictable in timing, direction and magnitude. Without removing your current thermocouples or RTDs from service for testing you don’t know for sure when they drift out of limits, all you know for sure is when they stop working altogether. Incorrect sensor data can be very costly. The SVS will not only give you the reliable temperatures you need (traceable to a NIST standard for the life of the sensor), but also provide advance warning of sensor decalibration so you never have to worry about whether the temperature is correct. It also provides greater operational life. Drift free measurements and timely preventative maintenance equals significant savings and increased profits. 

   Why is SVS better than redundancy or process modeling?

Many process control engineers use redundancy, and modeling such as energy and material balances to try to determine if sensors are reading correctly. Redundancy and modeling both require choosing from among several uncertain measurements. Sensor of the same type can fail in the same way so redundancy does not eliminate the uncertainty. Knowing for sure that one of the process control variables is correct (temperature) can significantly reduce that uncertainty in models, making them more effective Redundant or bundled thermocouples are somewhat better than single thermocouples. Averaging may identify a renegade TC that decalibrated rapidly. 

However, bundled or redundant TCs are usually of the same type and material and in some cases from the same lot of material, which exposes them to common mode failure. These bundles can drift collectively, usually in the same direction and at about the same rate resulting in an average drift or decalibration. Furthermore, the sensors in a bundle never measure the temperature at exactly the same point. This advanced technology (SVS) is similar to the word processor that was being introduced to office management community in the 1970s. They were very satisfied with IBM electric typewriters until they realized that there was a much better way. 

   Where has this been used and what results have others seen? 

The SVS technology has been used in very large scale brazing furnaces, verification of high-energy atomic waste process, safety interlocks in hydrogen cyanide converters, glass industry melters (combustion gasses and molten glass) and research laboratories, to mention a few.

Customers claim pay back of weeks and yields and performance enhancements in the millions of dollars annually. 

   How much longer with your device last in my operation?

In laboratory test SVS useful life is about twice the useful life of conventional thermocouple. You should see about the same multiple in your operations. Thermocouples constructed with AccuTru’s Mi-Dry dielectric have demonstrated 4X the life of thermocouples made with MgO. 

  Is SVS design to work only in very hot processes?

No, the SVS models cover temperature ranges from -200°C to +1750°C. Most of the early adaptors of this technology have been for higher temperature applications because drifting and other signal impairments usually occur more rapidly at higher temperatures. But accurate “calibrated” measurements are also required for processes operating at low temperature. 

  What is the concept behind Self-Calibrating and Self-Validating sensors?

Self-Validating Sensor technology is based on the ability to measure multiple, mutually exclusive thermoelectric properties of thermally sensitive materials contained in the tip of the sensor probe. The sensor probe is constructed like a thermocouple or RTD but is specially designed so that the thermal response of each element of the sensor can be monitored using independent combinations with multiple other elements. 

The signal conditioner/transmitter multiplexes these measurements and monitors the health of each individual thermal element using at least two of its electrical properties. This concept makes it possible to continuously monitor and “validate” each of the measuring elements inside the sensor while it is in service so that no element can drift without detection. If an individual element begins to drift or de-calibrate for any reason, the system eliminates the data for that element while still providing an accurate NIST traceable temperature with the remaining “healthy” elements. Using information about the number of “healthy” elements in the sensor, the transmitter then provides the operator or control system with sensor health status and notifies of impending loss of sensor validation before it occurs. Therefore an accurate and reliable temperature is reported for the life of the sensor. 

  How does the response time of the sensor compare to other thermocouples?

SVS probes have at least the same response time as thermocouples of the same size and sheath material. 

  Will the SVS transmitter work with my standard control?

Yes. The output signals can be configured in a variety of ways to interface with your standard controls. You will want to provide for use of the sensor health, however, as well as the temperature signal. 

  What does the SVS cost?

Temperature measurement systems vary widely in cost depending on the service. Initial cost of SVS will be higher that typical thermocouples, extension cables and signal conditioners by 2 to 5X depending of the size of the project. In applications where yields have been increased, false trips and unnecessary shut downs reduced or eliminated, fuel efficiency increased or emissions reduced, the cost of ownership have been significantly less.

  Can we lease your equipment?

In most cases, yes. 

  I don’t see my sensor configuration on the data sheet, are other options available?

Yes, contact AccuTru Customer Support 1.800.594.5737 for assistance. 

  Where do I get support?

AccuTru Customer Support 1.800.594.5737 for assistance.

  Can I try an evaluation unit?

Our evaluation units are in high demand and often in long term testing. We will be glad to provide you with one when they become available. Or we will lease you one or two units if you would like. 

  We do not have field mounted signal conditioners, the TC leads go directly into our control unit, can we do the same thing with the SVS?

The SVS sensor requires an SVS Transmitter. It provides your control system with the already linearized signal. Several options, either analog or digital are available for you to receive this signal into your control system. 

 

AccuTru's ExL Extended Life Sensors

  Aren't all thermocouples the same, what's different about the AccuTru AT ExL and AT ExL-C thermocouples?

All thermocouples are not the same. The majority of thermocouples in use today are metal sheathed (usually Alloy 600 or SS 316), mineral insulated (usually MgO) construction (MIMS). High purity alumina is most often used as sheath material for very high temperature applications. The quality of the materials used and quality of construction has a large effect on the thermocouple's performance and life. 

AccuTru's AT ExL metal sheathed thermocouples are constructed using very high quality materials and workmanship, plus the use of a proprietary dielectric (that replaces MgO or Al2O3) that has demonstrated greater signal stability and more than 4 time the life than similar sensor made with MgO. 

AccuTru's ExL-C is a high temperature Type R, B or S enclosed in AccuTru's proprietary closed end Al2O3 tube has demonstrated quality performance and longer life in closed end configuration. 

  Do I have to make modifications in my existing measurement and control system to use the AT ExL thermocouples? 

No.  AT ExL Extended Life thermocouples are installed exactly as your present TCs. 

  Exactly what is the difference between thermocouples made with MgO, your AT ExL TC made with Mi-Dry and the SVS? 

Features	T/C w/ MgO	T/C w/ Mi-Dry AT ExL	SVS
Self-validating, calibrating, in-service for the life of the sensor	NO	NO	YES
Readings traceable to NIST reference for the life of the sensor	NO	NO	YES
Advance warning, onset of decalibration or other signal impairments	NO	NO	YES
Longer life than T/C w/MgO in same environment	STD	YES, Up to 4X	Yes, 2X  (SVS/411 & 2311)
Greater stability than T/C w/ MgO in the same environment	STD	YES	YES