Landcal Blackbody Source
Type R1500T
User Guide
Page 14
8 Maintenance
8.1 Routine servicing
The source is fully tested and evaluated before supply and should give years of
trouble free operation. No regular servicing or maintenance is required. The
outer surfaces may be cleaned with a damp cloth. Do not allow water to enter
the case. Do not clean with organic solvents.
In the unlikely event of a failure we would recommend the source is returned to
a LAND company direct or to one of the LAND distributors for repair.
Sections 8.2 to 8.4 provide information for the customer replacement of
consumable items.
8.2 The heating elements
Silicon carbide elements oxidise slowly during use, resulting in increasing
resistance. The effect is offset by re-adjustment of the power regulator.
A time will come when the resistance becomes so high that correct adjustment
is unobtainable. At this point the elements must be changed.
In the event of an element failure, replace it in the manner described in Section
5.2. It is advisable to replace all elements if only one or two fail, because
new elements have a lower resistance than used ones which have aged. The
elements are series connected and the lower voltage drop across a new element
will tend to cause premature failure of the remaining older elements. The good
older units can be saved to make up a set of part worn elements.
8.3 The control thermocouple (Pt 13% Rh/Pt)
Replacement of the control thermocouple is carried out as follows:
1) Make sure that the furnace is not connected to the mains supply.
2) Remove the lower side panel not containing the controller.
3) Disconnect the thermocouple assembly from the insulation cylinder.
4) Disconnect the thermocouple from the connector block.
5) Remove the thermocouple from its sheath.
6) Fit the new thermocouple, connecting the positive leg (Pt 13% Rh) to the
positive side of the compensating lead (coloured red) and the Pt leg to the
green lead.
7) Re-connect the thermocouple assembly.
8) Replace the cover.
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