User Guide

PRESSURE PEN CALIBRATION for pressure ranges 2.5 bar to 40 bar

Mechanical calibration is concerned with the accurate setting of zero, span and linearity of the recording pen. The

adjustments detailed below must be performed in the order listed.

Unless a replacement mechanism assembly, bourdon or mechanical linkage is to be fitted it should not be necessary to make

coarse or linearity adjustments.

If it is not found possible to achieve one or more of the following settings, contact your nearest Rototherm Distributor or the

company itself.

1. Connect a suitable pressure regulator and calibrated test gauge to instrument pressure line.

2. Ensure all linkages are free to pivot and pens align and pass each other.

3. Fit a dummy chart plate and correct chart.

4. Radial red pen arm to ensure that pen nib tracks on chart time line.

5. Set pen to read zero on chart. Ensure pen zero adjust plate lies in-line with pen arm. Make small zero adjustment

using pressure take-off assembly on bourdon. Make large adjustments using horizontal link from pressure take-off

assembly to pen mechanism.

6. Overload the bourdon tube by 15% of the maximum pressure range before staring to calibrate and check for any

leaks. Release pressure.

7. Adjust the pressure so test gauge reads maximum pressure of the instrument range. If the recorder pen

does not read within ±1% full scale deflection of this maximum value, adjust the ratio post on the pen bracket

upwards to increase the scale length; downwards to reduce the scale length. Ensure to slacken and re-tighten the

ratio post-locking nut during any adjustment.

8. When the instrument is reading within tolerance for both minimum and maximum scale values adjust the pressure

to exactly half that of the pressure range of the instrument being calibrated.

9. Check the recorder accuracy is within ±1% full-scale deflection at this mid-point. If the instrument is reading low

the take-off assembly should be moved to the left by unlocking the centre fixing screw. If the instrument is reading

high at mid-point the take-off assembly should be moved to the right. Re-tighten the bourdon centre screw; adjust

the horizontal link to reposition the pen to mid-point and repeat steps 6 and 7.

10. When the instrument is reading correctly at all points make sure all links and screws are tight. Remove dummy

chart plate and replace with original.

11. Check calibration with recorder completely re-assembled before removing test gauge.

PRESSURE PEN CALIBRATION for pressure ranges 60 bar and above

1. Connect a suitable pressure regulator and calibrated test gauge to instrument pressure line or a certified