Temperature Calibrators

Calibration equipment is used in calibrating different Temperature units like: RTD, Thermocouple, pyrometer etc. The major applications are in:

• Black body Calibrators are used to minimize the emissivity errors in pyrometer.
• Black Body Furnace is used to calibrate non-contact IR thermometer.
• Reference Units are used in Industries, Laboratories and instrument shop.
• High temperature block furnace is designed for high temperature range calibration and finds application in the glass, electrical, power, automotive & material processing industries and laboratories.
• High Stability Block furnace has been designed for high temperature range calibration and finds application in the glass, electrical power, automotive & material processing industries and laboratories.
• Portable Calibrator is designed for medium range temperature calibration and find applications in the glass, electrical power, automotive and material processing industries.
• Liquid Calibration Bath is used in Laboratory.

Temperature Uniformity Surveys commonly referred to as a TUS, establish objective evidence of the heat distribution characteristics throughout an oven or furnace system. It also identifies the qualified work zone within the oven or furnace system. TUS’s can also be an effective way of determining the efficiency of the furnace system and to monitor furnace performance over time.

System Accuracy Test, commonly referred to as an SAT, is another critically important and often required test. System Accuracy Tests are performed to determine the error within the temperature control system (temperature control device/lead wire/thermocouple). Regardless of the application, knowing the error that exists in your temperature control system allows for more consistent control of quality.

Need of Furnace Calibration

The purpose of the uniformity survey is to determine the range of temperatures present at different locations in the furnace under normal operating conditions standards. It will cater the needs for uniform heating inside the furnace to match the product quality as well as process parameters.

• To achieve the highest possible accuracy, a sensor should be calibrated according to the system where it will be used.
• Even in manufacturing, same type of sensors yield slightly different readings from one another. Therefore, calibration is required to identify error.
• The sensor may give different output during storage, shipment, delivery and assembly.
• The sensor may give different output during storage, shipment, delivery and assembly.
• Sensor is subject to heat, shock, cold and humidity and may give a different output which is not acceptable.
• Sensor gets deviate with age which in turn does not give accurate reading. In order to get correct deviation, the sensor should be re-calibrated time-to-time.

• It provides the recognition to competent laboratories so that the customers can identify and select the reliable calibration, measurement and testing services for their needs.
• Labs are re-evaluated by accreditation body periodically to ensure that their standard of operation is maintained. The labs may also be required to participate in relevant proficiency testing programs between reassessments, as a further demonstration of technical competence.
• Accredited labs issue a test or calibration reports bearing the accreditation body’s symbol or endorsement, as an indication of their accreditation.
• Clients are encouraged to check the laboratory as to what specific tests or measurements they are accredited for, and for what ranges or uncertainties.

• Industrial thermometers come in a variety of forms and types, calibrating them can be quite complicated.
• To calibrate industrial sensors the laboratory must compare them to standard thermometers whose characteristics have been defined and are traceable to National Standards. Such thermometers that are traceable to national standard are known as ‘Master Sensors’.
• Master sensor is used as a reference sensor in comparison type calibration process.
• Master sensor is put in the highly stable temperature zone along with sensor under calibration, their reading is compared and error is calculated.
• Master should have high accuracy, and repeatability and should be recalibrated after certain period of time (generally time period suggested by calibration Laboratories).

A practical industrial or laboratory Thermocouple consists of only a single (measuring) junction; the reference is always the terminal temperature.

Possible measures are:

• Measures the terminal temperature accurately and compensate accordingly in calculating the measured value.
• Locate the terminals in a thermally controlled enclosure.
• Terminate not in copper cable but use compensating or actual thermocouple wire to extend the sensor termination to the associated instrumentation (compensating cable uses low cost alloys, which have similar thermoelectric properties to the actual thermo element). On this basis, there is no thermal voltage at the thermocouple termination. The transition to copper then occurs only at the instrument terminals where the ambient temperature can measure by the instrument; the reference junction can then be compensated for electronically.
  
• Use a temperature transmitter at the termination point. This is effectively bringing instrumentationclose to the sensor where electronic reference junction techniques can be utilized. However, this technique is convenient and often used in plant; transmitter produces an amplified (corrected) signal, which can be sent to remote instruments via copper cable of any length.