RSLogix 500 - Calculating Average

[laneslabaugh]

All -

I am writing a control panel program in RSLogix500 f/u/w a MicroLogix 1100 PLC controller.

I have 8 exhaust port temps stored in integer files and need to calculate the average.

The only catch is, I need to throw out any values in the event the measurement device (thermocouple) fails. i.e. our temp scanner sends a value of 1759 C in the event of a failed thermocouple.

Anyone have any tricks/ideas on an efficient way to do this?
I know I could use the brute force method of testing each value then summing the good values and counting the number of good values and then dividing, but I'm trying to write efficient code. Seems like there's got to be a better way....

 

[Mickey]

A little more info for the math gurus,would help.
Is this a running average? ( how long). 15 min, 1 hour, 1 month,average? etc.
How often do you want to take a sample?

Test the value before you add it to the sum. ( Less then or equal to its OK)

 

[laneslabaugh]

Sorry, it's a running average.

The values are read from MODBUS from the ECM. They update every second.

 

[Mickey]

See link below for a thread on the subject.

http://www.plctalk.net/qanda/showthread.php?t=37722&highlight=running+averag

 

[twdelectric]

Analog averaging

I have an application that is asking to average an analog signal based on the following:

72 hour averaging.
8 hour averaging.
Instantaneous average.

I will be using RS Logix programming software with a micrologix 1400 controller. Can I use FIFO instructions? I know I am limited with this to 128 words. This is a very slow control process so the sampling can be limited to taking a sample every 5 minutes.