Calibration System

In Response to the 2006 revision of the Aerospace Material Specification AMS2750D MICC Limited has designed a purpose built Automatic emf Calibration System.

AMS2750D Specification Covers pyrometric requirements for thermal processing equipment. The specification is used as a basis for the NADCAP certification programme.

The specification covers the following;

  • Temperature sensors
  • Instrumentation
  • Thermal processing equipment
  • System accuracy tests
  • Temperature uniformity surveys

Many First Class MI thermocouple manufacturers are seeking inclusion on the Qualified Manufacturers List (QML) within the NADCAP programme.

In order to do this company’s have to increase their calibration facility at least fourfold and seek to improve the relevance, accuracy and delivery of calibration data and to improve the archiving and retrieval of relevant data for analytical purposes.

AMS2750D requires suppliers to show evidence of conformity and accuracy of material. For MI Cable manufacturers this is achieved by sampling coils of cable prior to conversion into thermocouple sensors and producing calibration evidence for a number of stated reference points across the temperature range.

The MICC Limited Automatic Calibration System uses four furnaces fixed at four different temperatures and each furnace can accommodate up to 8 samples and a Reference Standard.

The four furnaces are controlled using Industry Standard temperature controllers. Each incorporates an EIA-485 interface allowing individual addressing and adjustment under computer control. The Temperature controller protocol ensures safe and secure digital communication.

The calibration system uses an individual Type R Standard Thermocouple in each furnace. For traceability this thermocouple requires its own calibration to National Standards, which must be carried out at predetermined intervals. The program therefore allows for entry of the calibration curve for each Standard thermocouple during the time it is being used in the furnace.

MICC Limited has designed this system to stay as close to the Physics of Thermocouple Calibration as practical in a production environment. Every piece of equipment used is either chosen or built to meet this criterion. Principally this involves keeping errors introduced into the measuring path as insignificant as possible.

Each furnace has 8 thermocouples and these are connected to a common block of gold-plated terminals.

The connector block can be disconnected from the cable and moved complete with its thermocouple load to another furnace, this simplifies the calibration process, as each furnace load only needs to be entered once.

For convenience the terminal boxes are held in place magnetically so they remain effectively fixed but can be lifted and easily moved.

The switch box is a purpose built instrument designed by TET Limited. It uses very low thermal emf and high insulation resistance reed relays. The box will switch any one of the 4 x 8 test thermocouples and 4 Standard thermocouples to the digital Multimeter. A microprocessor-based interface drives the relays and is commanded by a USB-2 input.

The system uses a 6-½ digit Digital Multimeter that can read 50-triggered readings per second via its USB-2 remote interface. The resolution is 0.1 microvolts on a 100.0000 mV range. The software runs on a standard 64-bit pc with four additional USB-2 ports. The operating system is 32-bit Windows XP Pro, which is most suited to this type of application.

Additional hard ware includes a bar-code scanner, a label printer, an external hard drive for data back up and a monochrome laser printer for test certificates.

This system is purpose built to suit the individual customer. We can change the presentation, the data manipulation and the language. Temperatures can be represented in Degrees C, Degrees F or K.

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