CM4 Four-Point Continuous Monitor
CM4 Technical Manual
E-14
Get Fault History - 0x3D
This command will query the unit for the latest fault(s). There can be
as many as four and as few as zero faults. General system faults are
indicated by bit 0 of the point status byte. If bit 0 is set to 1, bits 1-2
should be ignored. The point status byte is invalid for Fault 17 (Voltage
Fail) and Fault 18 (Relay Fail).
Command packet to instrument:
Command Code (0x3D) - 1 byte
Response packet from instrument:
Command Code (0x3D) - 1 byte
CM4 Date - 2 bytes
CM4 Time - 2 bytes
# of faults - 1 byte (0-4 maximum) (fault data, maximum of four
possible)
Date of fault - 2 bytes
Time of fault - 2 bytes
Fault # -1 byte
Point Status -1 byte
bit 0: General fault bit
0 = point specific
1 = general
bits 1-2: Point # where fault occurred
(ignored if bit 0 is 1 and for Flts 17 and 18)
00 = Point 1
01 = Point 2
10 = Point 3
11 = Point 4
bits 3-5: Undefined
bit 6: Previously Read
0 = new (not previously read)
1 = old (previously read)
bit 7: Instrument Fault
0 = maintenance fault -- the CM4’s ability to monitor is
not compromised.
1 = instrument fault -- the CM4’s ability to monitor is
compromised.
Get K-Factor - 0x3E
This command will inquire about K-Factor settings for all points. An
individual point is assigned with a K-Factor times 1000 (a K-Factor of
1.000 is sent as 1000). The K-Factor is used to change the sensitivity
of a point in the range of 0.200-5.000. This adjustment is made after
the calculation of concentration.
Command packet to instrument:
Command Code (0x3E) - 1 byte
Response packet from instrument:
Command Code (0x3E) - 1 byte
CM4 Date - 2 bytes
CM4 Time - 2 bytes
K-Factor (x 1000) Point 1 - 2 bytes
K-Factor (x 1000) Point 2 - 2 bytes
K-Factor (x 1000) Point 3 - 2 bytes
K-Factor (x 1000) Point 4 - 2 bytes
Status
0x00 = Point read
0xff = Read problem
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