ROC alarms Intouch

[cemass]

Hi guys,

I'm trying to configure a rate of change alarm on a setpoint tag so that when the operator types a number by error (exemple: 30 instead of 300) the alarm pops up and a with a confirmation message asking him if the setpoint he's trying to input is right. The problem i struggle with is once the ROC alarm pops up, i have no problem with acknoledging the alarm, but it never returns to normal.

I have linked a application script with my plc so that when i click a button it acks the alarm and another one that disables it but i want the alarm to return to normal (not just acked). Disabling it kind of works but then when i enable it the alarm comes back by itself even if the operatior hasn't put in a new setpoint

Might be a little stupid but i am not figuring it out

Thanks

 

[Steve Bailey]

That doesn't strike me as the most reliable way to prevent operator errors. There should already be maximum and minimum entry limits. You could also try adding logic to prevent changes greater than some percentage, You could also include logic to ramp from the existing setpoint to the new operator entry.

 

[drbitboy]

Show your code.

The State Coil/Fault Coil pattern is one way to implement an alarm circuit. In your case, the trigger should be the ROC event, but that event should be a one-shot i.e. when an ROC event occurs:

• the new value that caused the ROC event should be stored (in case the operator clicks the "yes I did meant that value" button to ignore the alarm),
• but the tag with the new value should be reset to the current setpoint.
  • So, if the operator clicks the "no I did not mean that value" to acknowlege the alarm, the ROC event will not reoccur, at least until another new value is entered.

 

[Bit_Bucket_07]

That doesn't strike me as the most reliable way to prevent operator errors. There should already be maximum and minimum entry limits. You could also try adding logic to prevent changes greater than some percentage, You could also include logic to ramp from the existing setpoint to the new operator entry.

One method that I have used to prevent unintended numerical data entries is to create a popup window to require the operator to enter the new value into two separate memory tags and only allow the new value to be accepted (and written to the IO tag) when the operator clicks the "accept" pushbutton if the two entries match.

This routine was not intended to replace the min and max limits, since the range of a valid entry varies with current plant conditions. It was only implemented to prevent the operator from accepting an accidentally mistyped numeric value, and was only used for a few critical data entries.

 

[robertmee]

Hi guys,

I'm trying to configure a rate of change alarm on a setpoint tag so that when the operator types a number by error (exemple: 30 instead of 300) the alarm pops up and a with a confirmation message asking him if the setpoint he's trying to input is right. The problem i struggle with is once the ROC alarm pops up, i have no problem with acknoledging the alarm, but it never returns to normal.

I have linked a application script with my plc so that when i click a button it acks the alarm and another one that disables it but i want the alarm to return to normal (not just acked). Disabling it kind of works but then when i enable it the alarm comes back by itself even if the operatior hasn't put in a new setpoint

Might be a little stupid but i am not figuring it out

Thanks

The ROC isn't clearing because the tag value doesn't have a new value to clear it. Stop trying to use Intouch scripting to solve logic issues. Use the PLC. Pretty simple logic to monitor a setpoint entry intermediate value, compare it to previous SP, and if it deviates, sets a bit. Use this bit in a condition script in Intouch to open your popup. Popup allows confirmation. Confirmation bit to PLC copies intermediate value to final value and clears the popup bit.