Servomex 07931001B, Operator'S Manual

Page: 129 / 221

07931001B revision 6 © Servomex Group Limited. 2020
115
The analyzer now checks that the measurement is stable. The criteria for judging
that the measurement is stable are as follows:
Both the concentration standard deviation and transmission standard deviation for
the measurement being validated must be below a certain level and must remain
below that level for a continuous period of time.
Both the threshold levels and the stability times are settable parameters. If the
stability criteria are not met within a timeout period, the auto validation process
continues regardless. This is different from manual validation where an unstable
measurement will cause validation to be aborted.
For the concentration, the stability threshold parameter is a standard deviation value
expressed as a percentage of the target measurement. For the transmission, the
standard deviation is just a raw value that is the standard deviation of the current
transmission ADC count.
So for example a concentration standard deviation threshold value of 5.0, a
transmission standard deviation threshold value of 15.0 and a stability time of 60
means that the standard deviation of the concentration must remain below 5% and
the standard deviation of the transmission must remain below 15 continuously for 60
seconds.
The registers are
•
concentration standard deviation
•
transmission standard deviation
•
Set Stability Time
•
Set Flush Time
•
Set Timeout Time
Refer to the Modbus map in section 12.1.14 for the register address.
The analyzer will now ask for the zero-gas to be turned on. Just to reiterate, the
Laser 3 Plus does not have the ability to control the external gas valves, so control
of the zero and span-gas valves must be done by the HMI / purge panel. The Laser
3 Plus will indicate on particular Modbus registers whether the valves should be
turned on or off.
Reading a 1 on a register means the valve should be turned on. Reading a 0 means
the valve should be turned off.
The HMI should monitor these registers every few seconds so that it knows when to
activate the valves
The registers are
•
Required zero-gas valve state