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Power
The AFM requires clean DC power of 11 to 28V at 1.4A (steady-state). During sensor
warm-up, the requirements are approximately 5A for a period of up to 1 minute. A good car
or motorcycle 12V battery can meet these specifications.
An AC/DC power supply is
available (P/N 1000A-7). The supplied wiring harness must be connected directly to the
power source. Do not modify the wiring harness without first contacting ECM.
Warm-up
After powering-up the AFM, it will take approximately 30 seconds for the control module to
bring the UEGO sensor to its operating temperature. It is okay to have the engine running
during this period. In fact it is recommended that a cold engine be started for a short period
(i.e. one minute) before the AFM is powered-up. The reason for this is to allow any
condensed water to be cleared from the exhaust system. Any liquid can thermally shock the
UEGO sensor.
For applications where the sensor is mounted in a tailpipe probe, it is especially important to
make sure that all condensed water is out of the tailpipe before the tailpipe probe is inserted
into the exhaust.
Analog Output
The AFM has a 0V to 5V linearized output suitable for input into a data acquisition or engine
control system. The analog output is available from the female BNC connector on the wiring
harness. For the AFM1000 only, the shell of the connector is signal ground and it is
electrically connected to the power source ground.
The measurement range for gasoline is 6.0 to 20.0 AFR. The relationship between the
1
analog output (Vout) and the AFR for gasoline
is:
[Equation 1]
AFR = 2.8 x Vout + 6.0 (gasoline only)
For example, if Vout is 1.0 V then the AFR is 8.8:1.
When the AFM is first turned on, the output passes through a sequence of three voltages.
Each voltage is held for five seconds. For the AFM1000, these three voltages are 0.0V,
3.06V and 5.0V, and correspond to 6.0, 14.56 and 20.0 AFR respectively.
For the
AFM1500, the three voltages are 0.5V, 3.06V and 4.5V, which correspond to 7.4, 14.56, and
18.6 AFR respectively.
The purpose of this sequence is to verify correct electrical
connection and signal conversion with the AFM and the data receiving device.
1
Assumes fuel H:C ratio of 1.85. For other fuels see the "Fuel Type Compensation" section.
5
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