I'm planning to utilize an analog output card, specifically the 1762OF4 model, to transmit a 4-20 mA signal to a variable frequency drive (VFD) for precise speed control. My configuration will set the VFD's 4-20 mA scaling, with 4 mA corresponding to 0 Hz and 20 mA corresponding to 100 Hz. Additionally, I'm going to configure the SCP input range, setting the minimum to 0 and the maximum to 1000. The scaled minimum will be set to 6240, while the scaled maximum will be 31200. I'm intending to store the input value in an N7 data file using an implied decimal. For instance, if I want to achieve a speed of 72.4 Hz, I would record a value of 724 in the N7 data file. Does this setup seem sufficient, or have I overlooked any important details?
I don't have the exact values for what 4mA and 20mA correspond to on that specific analog output card right now. However, if we assume that 6240 represents 4mA and 31200 indicates 20mA, then your description is accurate.
According to ASF, while I don't have the exact values for the corresponding outputs of 4mA and 20mA from that specific analog output card readily available, I can confirm that if we assume 6240 represents 4mA and 31200 signifies 20mA, then your understanding is indeed accurate. These figures are documented in the AB KBase technical note. Is there a method to indicate to future users reviewing the program that the decimal value is implicitly understood within the SCP instruction and its associated N7 data files? Or is the sole option to clarify this through a Rung Description?
JZerb inquired: Is there a method to indicate to future users of the program that the decimal is implicitly understood within the SCP instruction and the associated N7 data files? Or is the only solution to provide this information through a Rung Description? To elaborate, you could add a rung comment for clarification. Alternatively, consider utilizing a float data type instead of an integer to explicitly display the decimal point.
When it comes to Rung comments, they're essential for clarity. If I were to review your program and noticed a scaling from 0-1000 correlating to a drive output, along with an input value of 742, I would likely deduce the functionality accurately. To enhance understanding, it would be beneficial to label the N7 register with a clear comment like: Motor ABC Speed Reference (% * 10). This practice not only improves code readability but also aids in troubleshooting and maintenance.
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