Model 755A
Instruction Manual
NOTE:
The Zero and Span adjustments on the analyzer door are used only for the calibration of the digital readout for 0 to 100% oxygen.
The suppressed recorder ranges may only be set up after the digital readout has been calibrated. When setting up a suppressed recorder range, use only R41, R104 (setpoint) and R88 (Span) for adjustments. DO NOT
Example 2, Selection of a Zero- Suppressed Recorder Oxygen Range.
•Desired oxygen range for recorder output: 90% to 100%.
•Required span of 10% oxygen (100% - 90%) is selected when Recorder Oxygen Span Jumper is placed in the 10X gain position.
•Required zero suppression is 90% oxygen, thus Recorder Zero Suppression Jumper, is placed in 80% position, the highest setting below the zero suppression level, and R41, Recorder Zero Suppression Coarse Adjustment, and R104, Recorder Zero Suppression Fine Adjustment, are adjusted for the additional 10% required to reach the desired zero suppression level (90% desired level - 80% zero suppression Jumper).
b.Readout of Applied
In order to establish the precise zero suppression required for the desired recorder oxygen range, the actual applied zero suppression voltage may be read on the digital display.
Procedure:
1.Verify that Recorder Voltage Output Jumper is in the position appropriate to the recorder: 10 mV, 100 mV, 1 V or 5 VDC.
2.Place the front panel TEST switch in position 4, thus disconnecting the signal input to permit display of the
3.Temporarily place Recorder Oxygen Span Jumper in 100% oxygen (i.e.,
1X gain) position. The digital display will now read the applied zero suppression voltage in the range of
0.00volt (equivalent to 0% oxygen) to
10.00volts (equivalent to 100% oxygen).
4.Obtain the required zero suppression by appropriate combination of settings on the Recorder Zero Suppression Jumper and Recorder Zero Suppression Adjustments R41 and R104, as indicated by an exactly correct reading on the digital display.
5.Return the Recorder Oxygen Span Jumper to the normal operating position for the selected range.
6.Set the front panel TEST switch to position 1.
Example: With a highly expanded scale such as the 99% to 100% oxygen range of this example, a slight readjustment of R104 may be required to set the recorder pen at the precisely correct position on the chart.
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