Hofmann PMH-2, Руководство пользователя

Страница: 20 / 28

input. ‘Rotate’ until 7.00 shows on the display and ‘SAVE’. Offset is now
calibrated.
An offset calibration can only be performed if the pH is between 6.00
and 8.00. The display shows Err if a value outside these parameters is
present. ‘PUSH’ two times, the display shows “live” pH to allow the
operator to correct for a valid offset pH value. ‘PUSH’ now returns to the
offset calibration menu to repeat the procedure.
Rotate ‘CCW’ goes to End then ‘PUSH’ to exit. Rotate ‘CW’ proceeds
to the slope calibration.
SLOPE calibration.
Set the simulator lower than pH 5.50 or higher than pH 8.50‘
PUSH’ turns on the slope LED. ‘PUSH’ again, the slope LED now
flashes and the display shows “live” pH input. ‘Rotate’ until the correct
slope value shows on the display and ‘SAVE’. Slope is now calibrated.
An accurate slope calibration can only be performed if the pH is lower
than 5.50 or higher than 8.50 The display shows Err if a value inside these
parameters is present. ‘PUSH’ two times, the display then shows “live”
pH to allow the operator to correct for a valid pH value. ‘PUSH’ now returns
to the slope calibration menu to repeat the procedure.
Rotate ‘CCW’ two times goes to End then ‘PUSH’ to exit. Rotate ‘CW’
proceeds to mA calibrations. (See 4-20mA output)
Redox electrodes
Contrary to pH electrodes, redox (metal electrodes) do not exhibit
changes in slope or zero point. Nevertheless one may occasionally
experience wrong redox measurements, most frequently the cause being
a contaminated electrode. Cleaning and/or regeneration of the electrode
will cure the problem. It is very unusual to get wrong readings with redox
electrodes when using redox buffer solutions. The use of redox buffers
therefore is restricted to a simple function test of a redox electrode.
The mV offset and mV slope calibration modes of the PMH-2 are mainly
used to correct minor instrument offset or gain errors of the input section.
PAGE 20 PMH-2 Instruction manual