ECM pmCAN Module Instruction Manual page 16

The procedure for the calculation of particulate matter is as follows:
1. IST current is measured and using factory calibration data stored in the memory chip in the
sensor's connector, the factory particulate density parameters PMR (mg/m3) and PNR
(M/cc) are calculated.
2. The parameters PMR and PNR are then modified by the Delta Tables located in the
module to give PM and PN:
The Delta Tables are delivered from the factory full of 0s (zeros) so initially, PM = PMR
and PN = PNR.
3. PM and PN are then modified by the ZERO and SPAN processes:
When delivered from the factory, Mm and Mn are set to 1 and Bm and Bn are set to 0.
Thus, PM = PMR + Delta Table for PM and PN = PNR + Delta Table for PN.
When the user performs a ZERO or SPAN, the new M and/or B is stored in the
sensor's memory chip and used in Equations [3] or [4]. The Configuration Software
is used to perform the ZERO and SPAN procedures and also supports the cancelling
of the user calibration and returning Mm to 1 and Bm to 0 (or Mn to 1 and Bn to 0).
Calibration is the matching of an instrument to a defined standard. Due to the complexity of
PM, there is no absolute standard and as such, what is called PM often depends on the
scientific principle and application of the instrument being used. This is not to say that
various PM instruments available do not trend and approximate each-other, it is just that they
will not all match each-other to the degree, for example, that various NOx instruments will
match.
ECM's factory calibration is performed so that users of common laboratory-grade PM
instruments will get results that generally match what they see on their instruments. For
closer matching, the user can deploy the ZEROs and SPANs and Delta Tables features.
Although both ZEROs/SPANs and Delta Tables can be used at the same time, it is expected
that either one or the other will be used. Consistent with other instrumentation that ECM
manufactures, ZEROs and SPANs travel with ECM's factory calibration in the sensor's
memory chip while Delta Tables are in the modules. The reason for this is that once a user
determines the Delta Table for one sensor, it is likely that all ECM sensors with a factory
calibration will give similar results when connected to the same module. In addition, these
Delta Tables can be downloaded into other pmCAN modules. When determining Delta
Tables, it is important that the user looks at the PMR (or PNR) parameters or the PM (or PN)
parameters with the ZEROs and SPANs cancelled. Otherwise, the Delta Table(s) may be
specific to just that sensor (i.e. the Delta Table(s) should be a modification of the ECM
factory calibration, not a ZERO'd or SPAN'd version).
10
PM = PMR + Delta Table for PM
PN = PNR + Delta Table for PN
PM (new) = Mm x PM (old) x Bm
PN (new) = Mn x PN (old) + Bn.
[1]
[2]
[3]
[4]