Detcon FP-100 - Manual (Page 20)

Model FP-100
FP-100 Instruction Manual Rev. 0.0 Page 16 of 30
second) of the magnet over PGM1 and PGM2 will change the reading slowly. Holding the magnet
over PGM1 or PGM2 will change the reading more quickly. Use PGM1 and PGM2 to adjust the
output to match the target gas set-point. Assuming 50% of full range was applied adjust the reading to
12mA (120mV on the DVM, or 50% of full range on the display.
NOTE: 12mA and 50% of full range are based on the use of a span gas concentration of 50%.
If a different concentration of span gas is used, the mA reading will need to be calculated. I.E.
if a 25% concentration span gas is used the reading would be 8mA and the display would be
25% of full range. Use the magnetic tool to adjust the mA reading to the target set-point.
7. When the correct adjustment has been made, wait 15 seconds without holding the programming
magnet over either PGM1 or PGM2. The display (if connected) will flash “CAL” three times then
return to the target reading. If a meter is attached, the reading will momentarily decrease about 20%
and then return to the target reading. This indicates that the span calibration point has been
successfully saved. If a lack of proper signal level change is internally detected the sensor will
immediately go into fault. The display (if connected) will show “Fxx” (where xx is the error code). If
a meter is attached, the reading will go to 0ma. Only a successful re-calibration will clear this fault.
(Refer to section 5 Troubleshooting Guide.)
8. Remove the span gas and calibration adapter (or calibration wind guard). If a display is installed the
display will report a live reading as the sensor clears toward “0”. On the DVM, the reading will fall
from the reported span level to 4mA (40mV). The sensor now allows 5 minutes for the reading to
clear below 10% of full scale range (5.6mA). If the reading does not meet the clearing test criteria the
sensor will go into fault. The display (if connected) will show “Fxx” (where xx is the error code). If a
meter is attached, the reading will go to 0ma. Only a successful re-calibration will clear this fault.
(Refer to section 5 Troubleshooting Guide).
9. Span calibration is complete. If the Splash Guard was removed for calibration, re-install the Splash
Guard.
3.3 Gas Calibration Factor
Because of the catalytic bead sensor’s almost universal response to combustible gases, the FP-100 sensor can
be calibrated to specifically detect any of the combustible gases listed in Table 2. This gas is referred to as the
“target gas”. In addition, the sensor can also be configured so that it can be calibrated with any of the listed
gases regardless of which target gas is selected. This gas is referred to as the “cal gas”. These two features,
allow a significant degree of flexibility in the detection and span calibration process.
When calibrating with one gas (Cal Gas) and scale sensitivity is required for a different gas (Target Gas) use
the following calculation to determine calibration adjustment requirements: Target Gas Cal Factor ÷ Cal Gas
Cal Factor * Cal Gas concentration = Required adjustment level. For example, calibrating with 50%LEL
methane when propane is the target gas: 1.81(Propane) ÷ 1.00(Methane) * 0.5 = 90.5%. The sensor response
is lower for propane than it is for methane. Therefore, the scale sensitivity should be adjusted higher when
methane is used as the Cal Gas.
The Gas/Cal Factor Table shows the Gas Factors for most combustible gases that can be measured. Locate the
target gas and use the corresponding value as the Gas Factor. For example, if butane were the target gas, the
correct gas factor would be 1.71. If there is a mixture of target gases, use a weighted approach to determine
the correct Gas Factor. For example, if the target gas was 50% butane and 50% methane, the correct gas factor
would be calculated and entered as 0.5 * 1.71(Butane) + 0.5 * 1.0(Methane) = 1.35.
When a sensor has been calibrated with one gas and another gas occurs in the area of that sensor, the scale
response is calculated as: Cal Gas K-Factor/Target Gas K-Factor. For example, when a sensor has been