3000.doc Iss. 2/00
15
Probe Connection
THERMOCOUPLE INPUTS
When measuring thermocouples (Models 3000 & 3001) care should be taken to achieve the best
results. The inputs are via 4mm sockets and a range of thermocouple plugs are available for
connection. The input sockets are copper and behind the front panel to avoid the external effects of
draughts. The reference junction may be set in three different modes, the first is automatic (INT) and
Pt100 sensors are attached to the upper input sockets and monitor their temperature automatically
applying the corrections. The accuracy of the internal reference is approximately ±0.3°C to achieve
more accurate results, an external reference may be used (Ext), when using an external reference the
Pt100 input is used to sense the external reference temperature. The accuracy of this is as for Pt100
measurement ±0.01°C in addition to this there will be some errors due to the configuration of the
external reference, but generally with care, it is possible to achieve better results when using the
external reference mode. Finally, the reference junction may be switched off (OFF) and in this mode
the thermometer assumes a reference junction temperature of 0°C. This mode of operation is used
when an external automatic reference is used such as our RJ## series. Again using this mode of
operation gives slightly better results than will be achieved when using the internal reference.
CAUTION
When measuring thermocouples with the 3000 thermometer it should be remembered that the
temperature may be read to 0.01°C and this is equivalent to approximately 0.4µV per digit with a type
K thermocouple. Care must therefore be taken to avoid exposing the instrument inputs to draughts or a
heat source such as sun shining on the front panel. To obtain the best results the instrument should be
placed in a temperature controlled room and switched on for at least half an hour before measurements
are made. Running on battery power without the mains supply connected will also be of benefit.
When connected to the mains the batteries will be charged and additional heat generated inside the
instrument. Great care should also be taken to ensure that the correct materials are used when making
connections and avoid unnecessary joints of different materials as these again will cause small errors.
We offer a range of thermocouple connectors for use with the 3000 thermometer as well as a range of
automatic reference junctions and an external reference enclosure with integral Pt100 sensor, please
ask our sales staff for more information.
CALIBRATION
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