WIKA 70-8xx - Manual (Page 12)

GB
12
11472988.02 04/2013 GB/D/F/E
WIKA operating instructions expansion thermometer, model 70
7. Indicator check
Indicator checks should only be carried out in comparison with a more accurate
instrument or, if possible, with a calibrated instrument. The temperature during the check
must remain constant.
Fluctuating temperatures can lead to reading errors caused by the different response
times of the sensors.
With thermometers without thermowells, with a full and correct insertion length, a
minimum waiting time of 5 minutes must be maintained for temperature equalisation.
Temperature checks using thermometers with sensors assembled with thermowells can,
in many cases, only result in a reference temperature at the instrument under test, due to
permanent heat dissipation caused by the thermowell. In temperature applications fitted
with static checking thermometers (e.g. pipeline systems), permanent offsets in reference
temperatures can also be caused by the measuring path. Ambient temperatures around
the indicator case which differ substantially from room temperature can lead to steady
indication errors with constant ambient temperatures and to varying indication errors with
fluctuating ambient temperatures.
Permanent indication errors caused by the ageing of the measuring system can be
ignored, as they only account for a fraction of the indication accuracy.
8. Zero adjustment
WARNING!
Any interference with or modification to the instrument will invalidate the
warranty!
A zero adjustment may only be carried out by the manufacturer or in adequately equipped
workshops by qualified persons.
„ The electrical connection must only be made by qualified skilled personnel.
„ Connection of the switch via terminal box
„ Conductor cross-section max. 1.5 mm 2
„ The terminal assignment is stated on the connection label of the thermometer
7. Indicator check / 8. Zero adjustment