Detcon FP-524D INSTRUCTION MANUAL - Manual (Page 26)

Model FP-524D
FP-524D Instruction Manual Rev. 1.4 Page 22 of 39
Set Cal Factor is used to make the appropriate signal sensitivity adjustment when the cal gas is a gas other
than methane. This is necessary because the catalytic bead sensor has different signal strengths for each
combustible gas and all reading calculations are made based on a reference to methane. The cal factor value is
adjustable from 0.2 to 5.0. It represents the translation between the cal gas and methane gas, where methane
has a normalized cal factor = 1.0. For example, the cal factor for butane is 1.71 because the signal strength of
butane is 1.71 times lower than methane. The current setting can be viewed in View Program Status.
Table 2 shows the cal factors of most combustible gases that will be used as span calibration sources. Find the
gas of interest and enter that value the cal factor. For example, if propane were used as the cal gas, the correct
cal factor would be 1.81.
The menu item appears as: “Set Cal Factor”.
From the Set Gas Factor text scroll, hold the magnet over PGM1 or PGM2 until the “▼” prompt appears and
continue to hold the magnet in place for an additional 3-4 seconds (until the display starts to scroll “Set
Factor”). The display will then switch to “X.XX“(where X.XX is the current cal factor). Swipe the magnet
momentarily over PGM2 to increase or PGM1 to decrease the gas factor level until the correct value is
displayed. Hold the magnet over PGM1 or PGM2 for 3-4 seconds to accept the new value. The display will
scroll “Factor Saved”, and revert to “Set Cal Factor” text scroll.
Move to another menu item by executing a momentary hold, or, return to Normal Operation via automatic
timeout of about 15 seconds (the display will scroll “Set Cal Factor” 4 times and then return to Normal
Operation).
3.5.5 Set Bridge Voltage
Each Detcon plug-in combustible gas sensor requires a one-time setting for optimal bridge voltage. This is set
automatically during the “Set Bridge Voltage” sequence. The “Set Bridge Voltage” sequence determines the
required bridge voltage such that every plug-in sensor operates at exactly 200mA current. This technique
provides for tremendous uniformity in sensor-to-sensor operational performance, and it is notably better than
sensors that are operated on a common fixed bridge voltage platform. The range of bridge voltages required
for Detcon sensors is generally between 2.5 – 2.9VDC.
NOTE: The “Set Bridge Voltage” function is executed during factory calibration of every FP-
524D sensor. In the field, this menu item is only needed when a replacement plug-in sensor is
being installed, when mating a new FP-524D transmitter with an existing plug-in sensor or
when remote mounting the sensor away from the transmitter.
The menu item appears as: “Set Bridge Voltage”.
From the Set Bridge Voltage text scroll, hold the magnet over PGM1 or PGM2 until the “▼” prompt appears
and continue to hold the magnet in place for an additional 7-8 seconds (until the display starts to scroll
“Setting Bridge”). The transmitter will then display “WAIT”. During the 1-minute sequence, the transmitter
will display the three-digit number that corresponds to the bridge current as it is being adjusted.
At
conclusion, display will scroll “Set Bridge Voltage”. The new bridge voltage can be viewed in the “View
Sensor Status” menu.
Move to another menu item by executing a momentary hold, or, return to Normal Operation via automatic
timeout of about 15 seconds (the display will scroll “Set Bridge Voltage” 4 times and then return to Normal
Operation).