I want to include a control loop in my CR1000 to check for certain changes of state (e.g., door opening) and conditionally collect transient data at a relatively fast interval. I have two AM16/32 mutiplexers that measure at total of 56 temperature sensors, and normally would only be scanning these at 60 second intervals.
What is the minimum (fastest) scan rate that I would be able to use in my transient code to reliably collect data from the multiplexers? And how long could I allow this to run at this fast rate?
A sample of my code follows, for the first multiplexer only. The variable MUX_Interval is usually set for one minute (60 sec), but conditionally set to a lower value for a fixed period of time during a transient event.
If (TimeIntoInterval (0,MUX_Interval,sec)) Then
PortSet (6,1)
Delay (0,150,msec)
i = 1
SubScan (0,usec,16)
PulsePort (5,100000)
Therm107 (T(i),3,1,1,0,_60Hz,1.8,32)
i = i + 1
NextSubScan
PortSet (6,0)
Delay (o,150,msec)
EndIf
You may look in the Status table of the datalogger and find MeasureTime and MaxProcessTime. Those numbers are in microseconds. You program will be running in sequential mode, so just add those two numbers together to know how much time all the measurements and processing take.
What about the effect of mechanical cycling on the AM16/32 switches? Is there a physical limitation, or any recommendations on this?
Contact life rating is 5 x 10^7 operations. You can divide that by the number of scans you do in a day to estimate the life of the relays.