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5.0CALIBRATION______________________________________________
5.1INTRODUCTION
Calibration should be performed after any servicing involving the printed circuit boards. After calibration, perform a performance check as outlined in § 6.0.
Note: For instructions on disassembly of the unit, refer to § 7.0.
Calibration is facilitated by entering a special Calibration mode. See Appendix A1.
There are only two adjustments VR4 (the 41 °C comparator stage) and VR5 ( setting of the span of the A to D converter).
This calibration procedure may be carried out if the unit is thought to be out of calibration (E0x to E7x error messages in the display) or if any of the circuit boards have been replaced or repaired. In particular any repair that may have altered the potential of the ± 5 V rails or component change associated with the A to D converter would require a calibration check.
Calibration should be checked and performed after the unit has been running for at least twenty minutes; ie after the unit has warmed up.
5.2EQUIPMENT REQUIRED
♦41 °C calibration probe, available in MR700 series calibration kit (Fisher & Paykel part no. 900MR548).
For models with Revision D PCB and earlier:
♦Heater Wire module.
♦For MR480 only - jumper connector cable, which consists of two easy hooks connected in series with a 100mm length of cable and a 22 kΩ resistor.
5.3CALIBRATION PROCEDURE FOR MODELS WITH REVISION D PCBS OR EARLIER
(Before Serial Number 92XXAAA05495) (See § 9.0 for change history).
1 With models MR730/720/700 ensure that a Heater Wire module is connected, and that the Heater Wire switch is on (Heater Wire On LED should be on).
2Plug in the 41 °C calibration probe.
3Gain access to the adjustment potentiometers VR4 and VR5, by removing the control board from the humidifier front panel.
4With model MR480 only connect the jumper cable from pin 7 of U10 to the cathode end of D7 on the control board.
5With the Chamber Temp button held down turn on the power switch. Display should show
6Using the Chamber Temp button step through to number
7Adjust VR4 slowly so the display just changes from vertical to horizontal bars ( to ===). Back off VR4 and recheck that VR4 is not rotated past this display transition point.
8Using the Chamber Temp button step to number
9Remove the 41 °C calibration probe.
10Adjust VR5 for a display reading of zero. ( 0)
(This value may drift over time. A deviation of up to ± 2.0 will not affect circuit performance.)
11Calibration is complete; do performance check (§ 6.0).
5.4CALIBRATION PROCEDURE FOR MODELS WITH REVISION F PCBS OR LATER
(See § 9.0 for serial number details)
Ref. 185040646 MR730/720/700/480 Technical Manual ¯ Revision F ¯ Issued March 2001
