GE 90-30 374CPU Forcing AI's

Ok I am having issues forcing analog values in a GE 90-30 374 CPU. The "!" Enable/Disable Force is greyed out. When ever I do a write to the current value it just gets rewritten.

I keep reading in the help files about enabling the Change Management????? I am using Proficy Machine Edition 6.5 if that makes any difference.

You can only force discrete memory, not analog.

You could add a rung to ladder logic to move a value into the %AI memory.

Condition______

---] [--| Move |

        |      |

 %Rxxx  |      | %AIyyy

        |      | 

        |______|

When you need to force the %AI value, turn on the "Condition" bit and write a value to %Rxxxx. Put the rung at the beginning of the _MAIN program block.

Steve Bailey said:

You can only force discrete memory, not analog.

You could add a rung to ladder logic to move a value into the %AI memory.

Condition______

---] [--| Move |

| |

%Rxxx | | %AIyyy

| | 

|______|

When you need to force the %AI value, turn on the "Condition" bit and write a value to %Rxxxx. Put the rung at the beginning of the _MAIN program block.

Click to expand...

Can not force Analog's WTF?????? Man that means testing is going to be a pain. Obviously wanted to be able to force values so that we can see values on the HMI screens, to verify things are pointed to the right points. Oh well, guess that just means that I'll have to do something like what you mentioned for our testing.

Thanks for the response.

Oh one more thing since we are talking analog, scaling. From what I can see I am going to have to do all my scaling in the PLC code, ie there is no scaling instruction (I tried putting the SCALE_INT in my code but it will not let me)? Also my customer is using the IC693ALG223 cards, 4-20mA transmitters, with the low engineering units being 0. Based on all that I show the scaling be 0-4000counts = 4-20mA, and then have to scale according to what the transmitter's upper range is.

The 90-30 platform doesn't support the SCALE instruction. You will have to write ladder logic to scale the %AI value to engineering units.

Some 90-30 analog modules support scaling to engineering units in hardware configuration. The ALG223 is not one of them. If you select 4 - 20 mA range in hardware configuration, the raw data values will range from zero at 4 MA to 32000 at 20 mA. If you select 0 - 20 mA range in hardware configuration, the raw data values will range from zero at 0 MA to 32000 at 20 mA. If you select enhanced 4 - 20 mA range in hardware configuration, the raw data values will range from -8000 at zero MA through zero at 4 mA to 32000 at 20 mA.

Steve Bailey said:

The 90-30 platform doesn't support the SCALE instruction. You will have to write ladder logic to scale the %AI value to engineering units.

Some 90-30 analog modules support scaling to engineering units in hardware configuration. The ALG223 is not one of them. If you select 4 - 20 mA range in hardware configuration, the raw data values will range from zero at 4 MA to 32000 at 20 mA. If you select 0 - 20 mA range in hardware configuration, the raw data values will range from zero at 0 MA to 32000 at 20 mA. If you select enhanced 4 - 20 mA range in hardware configuration, the raw data values will range from -8000 at zero MA through zero at 4 mA to 32000 at 20 mA.

Click to expand...

Thanks Steve! That's what I was reading in the manual and just wanted to confirm. Luckily this is a small facility, so there are not a lot of Analog points, only about 25 total.