User Guide

18
TEMPERATURE PEN CALIBRATION
Mechanical calibration is concerned with the accurate setting of zero, span and linearity of the recording pen in comparison
with a known temperature read with a certified thermometer traceable to national calibration standards.
The adjustments detailed below must be performed in the order listed and the instrument must be allowed to settle before
readings and adjustments are made.
Unless a replacement mechanism assembly, temperature system or mechanical linkage is to be fitted it should not be
necessary to make coarse or linearity adjustments.
If it is not possible to achieve one or more of the following settings, contact your nearest Rototherm Distributor or the
company itself.
1. Allow the recorder to stabilise with the measuring element in a low temperature just above scale minimum.
2. The temperature recording pen should read within ±1% of full span at the correct temperature value.
3. If necessary, adjust pen fine zero adjust screw to bring the pen to the correct reading.
4. If the pen reading is significantly out i.e. more than 5 angular degrees, adjust the pen fine zero screw to bring the
pen arm in-line with the pen arm bracket and loosen the coarse zero adjustment screw holding the compensator
arm to the temperature bourdon tube centre. Adjust the pen to record true value, making a fine adjustment on pen
fine zero adjustment screw after the coarse zero adjustment screw has been re-tightened.
5. Allow the recorder to stabilise with the measuring element in high temperature just under scale maximum.
6. The temperature recording pen should read within ±1% of full span at the correct temperature value.
7. If necessary, adjust the pen reading by moving the link connecting the compensator arm to the ratio post on the
mechanism pen bracket.
8. In order to move the link, slightly loosen the locknut of the ratio post and by raising the pivot will increase the pen
movement whilst lowering the pivot will decrease the pen movement. Re-tighten the lock nut after adjustment.
9. Repeat steps 1 to 8 until no further adjustment is necessary.
10. Allow the recorder to stabilise with the measuring element in temperature equal to middle of chart span.
11. The temperature recording pen should read within ±1% of full span at the correct temperature value.
12. If necessary, adjust the pen linearity by loosening the coarse zero adjustment screw holding the compensator arm
to the temperature bourdon tube centre and moving the pen upwards if the reading is low and downwards if the
reading is high by a factor of 8 times greater than the reading error. Re-tighten the coarse zero adjustment screw.
13. To return the pen reading to the correct chart reading, adjust the linkage length between the compensator arm and
the ratio post pivot by loosening the two locking screws and sliding the links until the pen reads correctly.
Re-tighten the two screws.
14. Repeat steps 1 to 8 to check zero and span readings and steps 10 to 13 until all readings are correct to within
±1% of span at measured values.
Clearscan™ Recorder Series - Operating and Service Manual