Panametrics XMO2 - Chapter 3. Startup and operation; 3.1 Introduction; 3.2 Powering Up the XMO2 transmitter; 3.3 Establishing a sample gas flow

Chapter 3. Startup and operation
3.1 Introduction
This chapter provides instructions for starting up and
operating the XMO2 system. The following specific topics
discussed:
• Powering up the XMO2 transmitter
• Establishing a sample gas flow
• Calibration of the analog output signal
If you have not already done so, read Chapter 2, Installation,
for details on mounting and wiring the XMO2 transmitter, the
sample system, and any other optional equipment.
3.2 Powering up the XMO2
transmitter
The XMO2 transmitter does not have a power switch.
It begins taking measurements and generating an
analog output signal in the 0-25 mA range as soon as it
is connected to a 24 VDC power source. To power up the
system, simply energize the 24 VDC power supply.
Because the standard XMO2 measurement cell is controlled
at a constant 45°C (113°F) operating temperature, allow
at least 30 minutes for the unit to warm up and reach
temperature stability before taking any measurements.
During this time, you can establish a sample gas flow
through the system, as described in the next section.
3.3 Establishing a sample gas flow
Usually, the XMO2 transmitter is factory-calibrated at
a sample gas flow rate of 1.0 SCFH (500 cc/min) and at
atmospheric pressure. Unless otherwise specified on your
XMO2 calibration sheet, optional sample system tagging, or
optional sample system instructions, your XMO2 should be
operated at atmospheric pressure and at the flow rate listed
in Table 4 below.
Table 4: Recommended sample gas flow rates
XMO2 Type Flow Rate in SCFH (cc/min)
Weatherproof 1.0 ± 0.5 (500 ± 250)
Explosion-proof 1.0 ± 0.2 (500 ± 100)
Pressure-compensated 0.5 ± 0.5 (250 ± 50)
Note: For optimum performance, operating the XMO2 at
conditions other than those used for the factory calibration
requires that the unit be recalibrated at the actual field
conditions.
To establish a flow of sample gas through the system,
complete the following steps (see Figure 5 on page 7 as an
example):
1. Set the sample system ball valves to direct only the
sample inlet stream to the inlet port of the XMO2
transmitter.
2. Use the sample inlet needle valve to regulate the flow of
sample gas until the flowmeter reads the same flow rate
listed for your unit in Table 4 on page 13.
3. Read the resulting system pressure on the pressure
gauge. Make sure that there are no unnecessary flow
restrictions downstream of the sample system.
IMPORTANT:
For atmospheric pressure-compensated units, the XMO2
outlet port must be vented directly to atmosphere with no
restrictions, by installing all sample system components
and tubing upstream of the XMO2 transmitter.
4. Take a reading of the XMO2 4-20 mA analog output.
In some applications, pressure changes due to flow
rate changes can cause noticeable errors in the oxygen
measurement. In such cases, consider the following
corrective measures:
• Reducing the flow rate to the minimum recommended
value minimizes flow rate sensitivity. A bypass flow type
sample system (speed loop) allows minimum flow
through the XMO2 yet maintains a fast transport of the
sample gas to the XMO2.
• For the fastest transport, minimize the sample line
length from the process.
• If you cannot shorten the sample line length, reduce the
sample line pressure to less than 5 psig.
Proceed to the next section to complete the initial XMO2
startup.
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