Oldham WX16, User Manual

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WX16 User Manual | 33
jumper into 4-20mA position and installing the associated precision 100 ohm socketed
resistor allows 4-20mA signals to be applied to its C & A terminals. The 10-0192
sensor modules are not required for channels accepting 4-20mA.
Channels receiving input data from this board should have the Data From: menu set
for Sensor, as described in section 2.2.4. This activates Cal Mode menus described in
section 2.2.7 needed to zero and span sensor readings. After performing the one-time
only Initial Setup as described below, all subsequent calibrations are by the WX16’s
electronic Cal Mode menus.
*Catalytic sensors connected directly to the WX16 should be limited to ranges of 0-
1000ppm.
3.1.4 Catalytic Bead Sensor Initial Setup
Catalytic bead sensors vary widely in power requirements and sensitivity. It is therefore
important to configure each channel to match the sensor with which it will operate.
1. Prior to connecting sensors, apply power to the system. Note this PCB
requires 24 VDC power be connected to its TB2 terminals 1 & 2 as shown in
Figure 3.5. Suitable fused power is available from the Main I/O board’s TB2
terminal 10 & 12 (see Figure 3.1). Measure the voltage between each
channel’s A and R terminals and set the
Voltage Adjust potentiometers for the
correct sensor excitation voltage. This may range from 1.5 volts to 7.5 volts
depending upon sensor specifications.
Sensors may be damaged by
accidental over voltage conditions. It is recommended the Voltage
Adjust potentiometer screws be covered by a dollop of RTV or similar
material after completion of this procedure to avoid accidental over-
voltage conditions.
2. Remove system power and connect sensor wires to the R-C-A terminals.
Reapply system power and confirm correct voltage across each sensor’s A &
R terminals. Note: If sensor wires are long, it may be necessary to measure
the excitation voltage at the sensor end to compensate for I
2
R losses in the
wiring.
3. With the minus voltmeter lead on TB2-2 (common), connect the plus lead to
the channel’s test point. With zero air on that sensor, adjust its
Balance
potentiometer for .4 volts at the test point.
4. Apply 50% LEL combustible span gas to the sensor and allow the test point
voltage to stabilize. Two volts = 100% input to the A – D Converter and .4
volts = 0%. Therefore, 1.2 volts = 50%. Place the 3 position
Coarse LEL Gain
jumper into the position which reads between .8 volts and 1.2 volts on the test
point with 50% LEL gas on the sensor. Gain settings for each jumper position
are as follows: no jumper = 1, LOW = 7, MED = 21, HI = 41. Multiple jumpers
have an additive affect upon gain, so the LOW and MED jumpers together
provide a gain of 28.