Instruction Manual
Model 755A
If desired, the recorder output may be set for a fullscale range of 0 to 100% oxygen. Alternatively, a desired portion of this overall range may be selected for fullscale presentation on the recorder. The selection is made by an appropriate combination of scale expansion and zero suppression.
Scale Expansion
Fullscale oxygen span for the recorder is switch selectable for 1%, 2%, 5%, 10%, 20%, or 100% oxygen.
Zero Suppression
The desired zero suppression is obtained as the sum of (a) a jumper selectable fixed value of 0%, 20%, 40%, 60% or 80% oxygen and
(b)a continuously adjustable value of 0% to 25% oxygen. Thus the electronic circuitry provides the capability of setting the total zero suppression for any desired value from 0% up to a theoretical maximum of 105% oxygen.
However, the maximum usable zero suppression is 99%, which is used in establishing a range of 99% to 100%.
The effective zero suppression, in volts, may be read on the digital display by placing the front panel TEST Switch in position 4 and the Reorder Oxygen Span Selection Switch in 1 X gain position (i.e., 100% oxygen)
Example:
Desired oxygen range for recorder output: 99% to 100% oxygen.
Required span is 1% oxygen, obtained by jumper position.
Required zero suppression is 99% oxygen. Thus, fixed zero suppression of 80% oxygen is selected by jumper position, and adjustable zero suppression is set for 19% oxygen.
Voltage Outputs (Standard)
Provided a standard is a jumper selectable voltage output of 0 to 10 mV, 0 to 100 mV, 0 to 1 V, or 0 to 5 V DC.
Isolated Current Output (Option)
An isolated current output is obtainable with the optional Current Output Board, either included with the Model 755A or added at a later date in the field.
This option provides a current output of either 0 to 20mA or 4 to 20mA for a maximum of 850 ohms.
Refer to Section 8 Replacement Parts, for the part number of the Isolated Current Output option.
NOTE
Voltage and current outputs may be used simultaneously, if desired.
The oxygen readout is automatically corrected for pressure variations within 3% of the target value, which may be set anywhere within the range of - 2.7 to 3.3 psig ±3 psig
a.Alarm
The analyzer has an alarm relay assembly consisting of two
b.Case Mounting
The analyzer is supplied, as ordered, with hardware for one of three mounting arrangements: Panel, wall, or pipe stanchion.
c.Electrical Power
The analyzer is supplied, as ordered, for operation on either 120 VAC, 50/60 Hz, or 240 VAC, 50/60 Hz.
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