3/19/2022 11:38 AM | |
Joined: 9/8/2021 Last visit: 6/7/2022 Posts: 6 Rating: (0) |
Hello everyone! My name is Bill. I am building LOGO! based automation and monitoring for a 1kW AM transmitter. Logic-wise all is clear and working fine, but I want to be able to monitor transmission power. There is a Forward-Reflected power measurement system in the TX (transmitter from now on). It outputs from around 2.5VDC at 100W, trough 8.6VDC at 1000W, and I suppose (because as of this moment I don't have a powerful enough dummy load for 4kW, the peak output level of an AM 1kW transmitter), it will output up to 20VDC@4.5-5kW peak power. I will divide this voltage externally (scalable) to 0-10V, but the detector characteristic is not linear. I would like to be able at least to get a decent idea, I'm not looking for accuracy on this one. The transmitter receives (all signals 24VDC) a TX EN (enable), returns a contact closure on TX FAIL (for example something happens to the antenna system, and the reflected power rises above 20W - it shuts down and retries in a while). I have also built in 3 relays, that would allow me to set output power levels - when all are off, the TX pumps 100W carrier (default fold-back level after fail, to be able to check if all is OK at low powers safely), then sequentially, I have 500W, 750W and 1000W carrier. All these are fine. As I have a dummy-load/attenuator for up to 1000W, I have created an excel sheet with the detector output voltage at different levels, it's in the ZIP file, together with my program. I found an example from Siemens, (https://support.industry.siemens.com/cs/attachments/109783503/different_scale_analog_value.zip), added it to try to emulate a lookup table, but this bite is a bit too much for me - after all I am an RF engineer with very little experience in PLC's. Can someone help me to, at least, set the power reading coefficients properly at 1-2 low power levels, as soon I get the point I will deal with the rest? I need better accuracy up to 1kW, so I suppose using 4-5 of the available amplification branches there would make sense. I will use the rest up to the required 5kW max level. As soon as I get my hands on a powerful enough dummy load, I will build the detector characteristic up to this power level, but for now - let's focus on 0-1000W, where the biggest "bend" is and the accuracy suffers most. Thank you in advance! Bill 73 de LZ1SWE AttachmentLOGO PLC.zip (508 Downloads) |
3/19/2022 2:53 PM | |
Joined: 12/18/2014 Last visit: 10/5/2024 Posts: 33882 Rating: (4214)
|
Hello aetherlab, at first welcome to the forum. In attachment a solution. I hope this is what you need. AttachmentPAN TX_V2.zip (479 Downloads) |
3/20/2022 2:25 PM | |
Joined: 12/18/2014 Last visit: 10/5/2024 Posts: 33882 Rating: (4214)
|
You know how to use a linear equation to calculate a straight line segment? |
Follow us on