Delay in FP-RLY-420

[Nuts]

I am using the FP-RLY-420 with lookout to control a process. The process
requires interventions that are less than a second. I could not make
anything work, so I did a TREND of a latch that sets the relay on and off,
and on the same graph the status of the relay.

There is a lag of about one second from the time the latch sets on and the
relay goes on, and about 3/4 of a second on turning it off.

The manual says the responses are 8ms and 4 ms MAX.
What is wrong?
I am getting the runaround from the NI people.

Does anyone know the truth about how this works?

If we cannot rely on the NI written specs, what are they doing to us?

[Green_Rives]

Hello,

There are a couple of things that affect the speed of a system that uses an FP-1000. These include:

1. How often your application is polling the bank.
2. The time it takes to poll the bank (i.e. network latency, number of channels being polled, etc.).
3. The module�s reaction time to the command (i.e. the 6 ms typ. Spec.).

The default polling time for the FieldPoint object is 1 second. If you are using that object, it will write to the bank and then read from the bank at 1 second intervals. If you use the FieldPointOPC object (the preferred method), the system continuously polls the bank and will have a little bit faster reaction time.

The time it takes to poll the bank depends on the number of channels that you have. The document located
at ftp://ftp.ni.com/support/fieldpoint/Server/fp16_rates.pdf discusses how to calculate the time it takes to poll the module.

Last is the module�s actual reaction time. This is the 6 mS typ. time. When using an FP-1000, this time is much slower than the rest of the system, so it does not have much effect on your speeds. However, if you were running an embedded system, a write takes less than 1 mS, the speed of the module would have a greater impact on the system

For a Lookout system using an FP-1000, your worst case speed will be:

Polling time + network latency + relay operate time.

Sincerely,

Green Rives
FieldPoint Product Support Engineer
National Instruments