Scalling for analog input channel

[ckchew666 0]

Guys, I'm checking on some of the analog input at the SLC 5/04, I couldn't understand some input (min & max) & scaled input (min & max) settings. 1) For example, I tried to inject 4-20 mA into one of the analog channels (completely remove all the 2 cables at the channel), I managed to get the below reading at RSLogix 500: Inject (mA) Value 4 3271 8 6545 12 9818 16 13094 20 16368 But at the SCP instruction Input = I:6.3 (3150) Input Min. = N7:56 (3175) Input Max. = N7:57 (9007) Scaled Min. = N7:66 (0) Scaled Max = N7:67 (5000) Output = N7:174 (-21) a) I taught the Input Min shall follow the inject value of 4 mA, which is 3271? b) The Input Max. value shall follow the inject value of 20 mA, which is 16368? The field device is a 4 - 20 mA pressure transducer. 2) while for another analog input module; Inject (mA) Value 4 3274 8 6551 12 9827 16 13106 20 16383 But at the SCP instruction Input = I:7.1 (0) Input Min. = N7:58 (1507) Input Max. = N7:59 (0) Scaled Min. = N7:68 (0) Scaled Max = N7:69 (5500) Output = N7:160 (5500) c) The Input Min. is larger than Input Max.? The field device is a pressure transducer using 4 - 20 mA. Both analog input module is 1746-NI4.

[finfin 0]

Yes, it looks like the input min and input max are wrong in both cases. You have the right Idea. The min should be 3277 and max should be 16383.

[bikerdude 0]

ckchew666, Looks like someone may have stepped on your N:56 thru N:69 values. Make sure they aren't being used in another rung/instruction. 4ma = 3277 is normal 20ma = 16383 is normal Of coures these numbers can be changed somewhat to allow for on site calibrations. BD

[finfin 0]

I wondered the same thing as Bikerdude. If you don't want them to be changed, you can enter the values instead of the addresses...tweeking at runtime becomes more difficult and in some cases impossible. I commonly use values values for the Input Min and Input Max and addresses for the scaled min and scaled max (so different sensors can be scaled from the HMI).