201.028 REV 1 Date of Issue: 18 June 2018
6.4.1.2.4 AS4059E-2
AS4059E Table 2 also has some similarities to NAS1638. In terms of the representation in Modbus registers, the
main differences are an extra 4-6μm(c) size range and the addition of an extra ``000’’ class. This is represented
using the number -2. If the user program interprets this as a positive number it will appear as 65534 (0xFFFE hex).
6.4.1.2.5 Temperature and Water Content Measurements
These are contained in the TEMPERATURE register 33 and the RH (relative humidity) register 34. These are scaled
by a factor of 100, so that values of 12.34°C and 56.78% RH would be represented by values of 1234 and 5678
respectively. The temperature can go negative, in which case the usual ``twos complement’’ representation is
used. Most controllers should have a facility for reading ``signed integers’’ encoded in this way (these will appear
as large positive numbers if interpreted instead as positive numbers, for example 65535).
The special value -32768 (0x8000 hex) is again used to indicate ``No result’’, as per the contamination result
codes. This could be due to a sensor failure or to the unit still in the process of powering up.
6.4.1.3 Performing Tests
6.4.1.3.1 Commanding Test Start
If the CMS is monitoring a single machine, it will normally be configured to test continuously and automatically, so
that the contamination measurement can be read out at any time as described above. However some
applications need a defined test start and test end, for example end-of-line production testing, where each result
relates to a separate item being tested.
These applications can simply use a push button (or relay) wired to the CMS start signal, or the front panel push
button, or can be commanded programmatically via Modbus.
To start or restart a test, write the value 1 to the command register 21. The test duration can be set using RMF-
View before installation, or alternatively write the required test time (in seconds) to the TEST DURATION register
18.
6.4.1.3.2 Test Status
A test status code is available in register 30. This contains a number indicating the current state of the CMS,
according to section 7.2.2, table 7A. This allows a system to remotely monitor the CMS operation, if desired,
allowing more specific diagnostics.
NOTE: the fault conditions are also indicated on the front panel LED, while ``No Result’’ in the case of a fault is
indicated using special result values as previously described.
6.4.1.3.3 Test Completion
The TEST COMPLETION is indicated by register 36. This contains a number between 0 and 1000 indicating the test
progress (this is also used by RMF-View to drive the test progress bar).
6.4.1.4 Particle Counts
Some quantities are (or may become) too large to fit into a single 16-bit register. For example the 4μm particle
count could easily be more than 65535. These items are represented using two consecutive registers; the
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