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Using a Analog/Analog Compare channel with analog CAN inputs
Hi,
I have two modules that are external to IQAN. Each supplies a weight value via two independent J1939 CAN parameters. One module is at SA=0xEB and the second is at SA=0xEC.
I need to compare these and enunciate a fault if there is a difference in force that is > 25 LbF. I tried using the AAC channel to do a DiffCheck and it does not work. The AAC is always TRUE even when both channels are with 10 LbF of each other. I thought that maybe it's due to the startup delay of these modules so put a 1000mS delay on the AAC DiffCheck ENABLE input and it still comes up TRUE. I then set the Primary Input to be the same as the Secondary input and it still comes up TRUE, even through the two inputs to be compared ARE THE SAME. Note, this is in IQANdesign v6.08. Is it possible to use the AAC for this? If so how?
Customer support service by UserEcho
The AAC is True when you are within the diff check limit.
The AAC is False when the difference between the channels is larger than the diff check limit.
Gustav,
You must have missed the sentence where I stated I used the same input for both the Primary Input and the Secondary input, and it still goes TRUE (Faulted) even when it is comparing the same input!!! I am using these on actual analog inputs from joysticks and it works great. It is NOT WORKING when I use it with "analog inputs " that are derived from CAN parameters
Gustav,
Looks like I'm the one who missed it. For whatever reason I was thinking that when the AAC is TRUE, there is a fault. Thank you for the explanation, which forced me to look at things deeper.
One last comment in case anyone else ends up looking at this post. I did find that it takes 3000 mS before the external modules wake up and start outputting the two "analog" weight values I was trying to compare using the AAC. I have added a delay of 3500 mS for the AAC channel Enable to insure it is getting valid data to make the comparison with