We use AC450 & S100 in our plant. Very often we received signal error in the AI loop and it is back normal by itself in 0.1-1 second. This is happening very randomly JUST in AI signals.

Description our system (HMI ABB Advant OCS & Process Portal A).
Current loop 4-20 mA:
- transmitter 4-20 mA
- power supply 24 VDC
- barrier IN 4-20 mA/ OUT 4-20 mA(for anti surge controller)
- connection unit on DCS (alarms go by MODBUS)
- connection unit DSTA131 (was replaced)

Analog input for AC450 (from DSTA131):
- cable DSTK221L3 (was replaced)
- AI card DSAI130A (was replaced)
- cross card DSBB172B
- 2x bus extension cards DSBC174
- 2x terminator cards DSTC176
- 2x CPU cards PM511V (in AC450)

We lose the signals (by trends) ONLY on HMI Advant, on DCS - nothing. We have alarm signals on HMI Advant, local panel, printer (sometimes), DCS (sometimes).

Can You help Me?

 

Hi Dima,

I was wondering if you had been able to resolve the issue.

> We use AC450 & S100 in our plant. Very often we received signal error in the AI loop and it is back normal by itself
> in 0.1-1 second. This is happening very randomly JUST in AI signals.

> Description our system (HMI ABB Advant OCS & Process Portal A).
> Current loop 4-20 mA:
> - transmitter 4-20 mA
> - power supply 24 VDC
> - barrier IN 4-20 mA/ OUT 4-20 mA(for anti surge controller)
> - connection unit on DCS (alarms go by MODBUS)
> - connection unit DSTA131 (was replaced)

> Analog input for AC450 (from DSTA131):
> - cable DSTK221L3 (was replaced)
> - AI card DSAI130A (was replaced)
> - cross card DSBB172B
> - 2x bus extension cards DSBC174
> - 2x terminator cards DSTC176
> - 2x CPU cards PM511V (in AC450)

> We lose the signals (by trends) ONLY on HMI Advant, on DCS - nothing. We have alarm signals on HMI Advant, local panel,
> printer (sometimes), DCS (sometimes).

 

It seems the 4-20ma loop fault and not the DCS.
The 4-20 loop is fluctuating.