Seaward DP6 - Manual (Page 13)

Operating Instructions Thermocouple Calibrator Type DP6
12
APPLICATIONS
THERMOCOUPLES
A thermocouple consists of two conductors of dissimilar material which have a
common junction at which the conductors are in good thermal and electrical
contact. This point of connection is known as the measuring or hot junction. The
other ends of the conductors are connected to an instrument which will measure
electromotive force and the point of connection is known as the reference or cold
junction. If heat is applied to the measuring junction, an emf will be generated which
can be measured. The magnitude of this emf is dependent upon the difference in
temperature between the measuring and the reference junction. Consequently, when
using thermocouples or calibrating thermocouple measuring instruments, it is
necessary to determine the temperature of the reference junction and then add or
subtract its value to or from the temperature difference according to whether
positive or negative temperatures are being measured or simulated. The concept
seems very complicated, but when using the DP6 to measure or simulate
temperature, all the above is automatically taken into account and the user can
proceed with confidence.
MEASUREMENT OF TEMPERATURE
The DP6 is an accurate and versatile instrument for the measuring of temperature
using thermocouples as the sensing element.
It can display the temperature in degrees Centigrade, Fahrenheit or absolute Kelvin.
Connect the thermocouple to the terminals at the rear of the DP6 (ensure the correct
polarity). The red-based terminal is the positive and all-black terminal is the negative
connection. For those thermocouples terminated with a miniature thermocouple
plug, an all-copper connection socket is provided as an accessory. This plugs
straight into the DP6 terminals and may be used with any thermocouple type.
The thermocouple type and measure mode must be now configured using the right
hand display, and the value measured will be shown in the left hand display. The
resolution will be 0.1 degrees for Centigrade, Kelvin and Fahrenheit. The cold
junction compensation is automatic and the temperature displayed is the true
temperature at the thermocouple hot end. It should be remembered that whilst the
DP6 is an extremely accurate measuring instrument, when assessing the overall
accuracy of the measurement the uncertainty of the thermocouple used should
be included.