For better or worse the project I am working on has specified several equipment elapsed time meters that are supposed to have their values displayed on an HMI, but don't have any hardware interfaces - so apparently they are meant to be purely software based.
So I am looking for ideas for a persistent software based elapsed time meter that runs on an Rx3i PLC and also has a Cimplicity based HMI.
My experience tells me that anything that is Rx3i based is subject to being written over when someone does a download. (yes, you could specify a policy of don't download initial values - but you can't enforce that). But it may be that I don't know everything about an Rx3i. So is there any hidden corner of operation that would allow for a persistant software defined elapsed time meter?
Another alternative is to leverage the database in the HMI to accumulate time. But that requires a working HMI system to record the data - And a working HMI is not a requirement for the equipment to operate.
Any suggestions on things I might have missed?
Yes I know you can buy Ethernet connected elapsed time meters for only relatively small $$$, and I suggested doing this when I understood the consequences of the requirements - but that idea was shot down (and stupidly too IMHO)
So I am looking for ideas for a persistent software based elapsed time meter that runs on an Rx3i PLC and also has a Cimplicity based HMI.
My experience tells me that anything that is Rx3i based is subject to being written over when someone does a download. (yes, you could specify a policy of don't download initial values - but you can't enforce that). But it may be that I don't know everything about an Rx3i. So is there any hidden corner of operation that would allow for a persistant software defined elapsed time meter?
Another alternative is to leverage the database in the HMI to accumulate time. But that requires a working HMI system to record the data - And a working HMI is not a requirement for the equipment to operate.
Any suggestions on things I might have missed?
Yes I know you can buy Ethernet connected elapsed time meters for only relatively small $$$, and I suggested doing this when I understood the consequences of the requirements - but that idea was shot down (and stupidly too IMHO)