HC900 disabling a sensor input

Hi,

I have many thermocouple inputs linked to a min-max-avg block. If I allow a user to disable an input via a digital variable, the value goes to the default zero. In other words, a valid number. Same for the failsafe. Is there a way to get a sensor input's value taken out of a calculation when it goes disabled, warn or fail? In other control systems I'd generally find a way to pass an NaN or +inf or some invalid value that the calculation objects would ignore. As it is, these default sensor values get calculated into the min, max and avg of that block.

Any help is greatly appreciated!

archy

The 'max' reading will still be valid

If you know how many have been disabled then the average can be corrected by multiplying the average by the total number of sensors then divide by the number of valid sensors.

The minimum is more difficult. it will be zero. Unless you get a sorted list which you can search you will possibly have to roll your own, ignoring the invalid zeroes.

Thanks, Bernie. I looks like I should be okay, then, with the max and average. Does the HC900 have a sorted list object or would this have to be done in code? I guess I'll have to put some thought into finding the lowest non-zero number.

Thanks, again, for your input.

If looks like Honeywell has already done the work to throw out deviant data:

I see. This is terrific! Thanks for pointing it out to me, danw!