MAN0905_Issue 7_07/17
Searchpoint Optima Plus with optional HART
®
output
Operating Instructions
2108M0550
30
5. Operation
During normal operation, the 4-20 mA output represents 0-100 %FSD. The output is linear.
Analogue output below 4 mA represents diagnostic information. If the Searchpoint Optima Plus measures
a negative gas reading, the analogue output will remain at 4 mA until the negative gas warning threshold
is reached (-3 %FSD to -6 %FSD depending on the gas being measured) at which point it will signal a
Warning.
5.1 Default Configuration
Status
Current output
Fault
< 1 mA
Warning
3 mA
Gas Reading
4 – 20 mA
Overrange
21 mA
Inhibit
2 mA
The tolerance on the nominal current output value is ± 0.2 mA.
During Warning status, the Searchpoint Optima Plus will continue to monitor gas, and will revert to Gas
Reading status if a gas reading is detected.
If a Warning is indicated, schedule maintenance to investigate and rectify the cause. If left unattended, the
unit is likely to enter Fault status, when it will be offline.
The Warning, Inhibit and Overrange signal levels can be configured using the HART
®
communications, or by
a Honeywell Analytics Field Service Engineer as follows: -
Parameter
Range
Warning*
0 mA to 6 mA
Inhibit
1 mA to 3 mA
Overrange
20 mA to 21.6 mA
* For ATEX compliance, the warning value should not be set > 3 and < 5 mA. If the warning value is set
higher than 4 mA, the output signal will toggle between the warning value for 1 s and the current gas
reading for 9 s.
5.2 HART
®
Operation during Fault
HART
®
communication requires > 1 mA current output for transmission, therefore if the HART
®
version of
the Searchpoint Optima Plus goes into Fault the HART
®
communications will not work.
It is possible to configure the Fault output level of a Searchpoint Optima Plus unit with HART
®
to be 1 mA.
This can be done during commissioning (see Commissioning using HART
®
Communications, Configure
HART
®
Operation during Fault).