RMF Systems CMS 2 - Analogue 4-20 Ma Modes

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As a policy of continual improvement, RMF reserves the right to alter the specification without prior notice.
201.028 REV 1 Date of Issue: 18 June 2018
6.4.2.2.3 CAN2.0A and CanOpen
The 11 bit format is designed to be compatible with the CanOpen standard. It can also be used with any system
that allows raw CAN-bus 2.0A identifiers to be received.
In order to use 11 bit identifiers (CAN 2.0A) set a value below 0x7ff for the ``Base Address’’.
For a CanOpen network, use a base address of 0x182 for example. This will result in message IDs corresponding to
the CanOpen ``pre-defined connection set’’.
6.4.2.3 Operations
6.4.2.3.1 CAN-bus Settings
CAN-bus physical layer
ISO-11898-2
Protocol type
CAN2.0B (29 bit identifiers)
CAN2.0A (11 bit identifiers)
Baud
User Set 1M/800k/500k/250k/125k/100k/50k/20k/10k
Identifier Range
User Set
6.4.2.3.2 Operation
Typically the installer will have configured the CMS to automatically start continuous testing. At the end of each
set test interval (e.g. 2 minutes) the CMS will emit a CAN ``Result Codes’’ message using the set CAN identifier
(e.g. 0x18FFB53F using hexadecimal notation). So a typical CAN message might be:
Byte
Identifier
1
2
3
4
5
6
7
8
0x18FFB53F
12
8
2
Details of the CAN-bus messages supported are in 11.2
See appendix 11.2 for more an example walk through and messages.
6.4.3 Analogue 4-20mA Modes
The CMS provides two analog 4-20mA current loop outputs, A and B. In order to provide the possibility of
transmitting more than two parameters, several different modes can be chosen to suit the application.
6.4.3.1 Fixed – NAS1638 and RH
The CMS result format must be set to NAS1638. The outputs then simply indicate the NAS1638 contamination
class and the RH level as follows:
Output A
Contamination Code
=mA-5
4mA NAS 00
5mA NAS 0
6mA NAS 1
…
17mA NAS 12
20mA OVERRANGE
Output B
RH%
=(mA-4)*100/16
4mA 0% RH
5mA 6.25% RH
20mA 100% RH