ECM pmCAN Module Instruction Manual page 15

battery). Grounding the case of the pmCAN module to the vehicle can sometimes help as
well. A good noise test is to mount the sensor in an exhaust with no flow (i.e. engine off) and
to collect 0.5 minutes of parameter "IST" (sensor current) data at a sample rate of 10 ms and
an averaging alpha of 1 (i.e. no averaging). This can be easily performed using the supplied
Configuration Tool software and plotted using Excel. IST should have less than ±0.5 nA of
noise.
Cleaning: Occasionally the sensor will get fouled with PM. When this occurs, the electrodes
will be shorted and the VHV parameter 1000V±100V potential will be unable to be
maintained. When this occurs, take the sensor out and blow it out with air for about 10
seconds. Sometimes blowing the sensor out won't clear it so it has to be disassembled and
cleaned. This takes only a few minutes. See Appendix G. Keep in mind that after blowing
out or cleaning the sensor, it will be need to be operated in an engine for a period until it
reseeds.
Indicator Light: On the front of the pmCAN is an indicator light which tells the status of
pmCAN. When the light is solid red (ie. not flashing), the high voltage electrode is turned
off and the sensor can be removed. When the light is solid green, the high voltage electrode
is at 1000 V. The meanings of the light when it is flashing is explained in Table 3. PM, PN,
PMR, and PNR are set to -1 if there is an error.
Calibration: All PM Sensors supplied by ECM are factory-calibrated. This calibration is
stored in a memory chip in the sensor's connector and is read by the module. Fortunately, the
sensor's calibration is robust and will not change with age or disassembly/cleaning. Sensors
can be sent back to ECM for a calibration check and repair if they are damaged.
The user may recalibrate or modify the output of the pmCAN in two ways: ZEROing
and SPANing, and using Delta Tables.
ZEROing and SPANing: PM (units: mg/m3) and PN (units: M/cc) can be individually
ZERO'd and SPAN'd. The results of the ZEROs and SPANs are stored in the memory chip
in the sensor's connector along with the factory calibration. A ZERO and SPAN can be
cancelled, returning to the sensor to the factory calibration. Always perform a ZERO before
a SPAN.
Delta Tables: The purpose of the Delta Tables is to allow the user to modify the factory
calibration of the pmCAN to match another PM analyzer. With Delta Tables, the user
recurves the calibration of the sensor by different amounts at different PM levels.
Interpolation is performed between the points in the tables. Unlike the ZEROs and SPANs,
the Delta Tables are stored in the pmCAN module and are applied to any sensor attached to
that module. The Delta Tables are entered and programmed into the pmCAN module
using the Configuration Software.
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