HI,

How do i compare the values of two (or more) channels in the Sensor Factory and alert if they return different numbers.

Details:

I have a checksum that runs on a database table, it returns a number, this checksum runs on what should be identical copies of this database.

so i have Channel Definition

#4:NS4SUM 
channel(5087,2) 
#5:NS5SUM 
channel(5088,2)

and i want to go into error state when channel(5087,2) <> channel(5088,2)

I tried

Status Definition

#1:Comparison
(channel(5087,2) - channel(5088,2)) = 0

or

Status Definition

#1:Comparison
(channel(5087,2) <> channel(5088,2))

or

Status Definition

#1:Comparison
(channel(5087,2) != channel(5088,2))

and none of them went into error state when the channels reported differnt values. How can this be done? Also, can i compare 4 channel values and go into error state if any of the values differ from the others?

Thanks,

-chuck

Article Comments

Hello,

the Status-Definition field can only handle expressions with the STATUS(...)-command, not the normal channel-definition formulas.

best regards.


Jun, 2012 - Permalink

Can you provide more details beyond "what you are doing is wrong" to help me solve my problem?


Jun, 2012 - Permalink

Okay, you cannot use the Status-Definition field for such calculations. So, why not creating a 3rd channel with

#3:Comparison
(channel(5087,2) - channel(5088,2))

and then setting Error-Limits on this channel so that everything below and above 0 sets the sensor into an Error state?


Jun, 2012 - Permalink

Thanks, that was helpful.

For documentation purposes:

I wanted to make sure a (small) mysql database table was being replicated properly, so i created a MySQL sensor on each database that did a query like this:

select SUM(name + content) from records

this returns a number that is used in a Sensor Factory channel definition where i compare the two values by subtracting.

The sensor numbers are 5099 and 5096 and the channels (as listed under mysql channels tab 'Value ID') were both 2.

  1. 1:Table1vsTable4 (channel(5099,2) - channel(5096,2))

This value should always be 0, so setting the sensor factory sensor to alert when channel Table1vsTable4 was greater or less than 0 worked great.


Jun, 2012 - Permalink