Analog input with ML1500

[308 0]

I'm using a ML1500 with a 1769-IF4 analog input card. I need to use two ultrasonic sensors to measure the level of two storage tanks and the sensor have to indicate if either tank is full. These sensors have 4-20mA output. My problem is that I have no idea whatsoever in programming analog inputs. What should I do and how do I write the program to meet the application needs? How do I connect the sensors to the analog card? Thank you in advance.

[BobLfoot 301]

This almost sounds like a request for help with a first year electronics project, but I'll assume that it sounds that way because Englich is not your native tongue in Malayasia. I'd offer the following advice. 1. List out in some fashion what you want to happen when the tank is empty? A. Does the sensor give 4ma or 20 ma? B. What valves will be opened, what will be closed? C. What motors will turn on and which will turn off? 2. List out in some fashion what you want to happen when the tank is full? A. Does the sensor give 4ma or 20 ma? B. What valves will be opened, what will be closed? C. What motors will turn on and which will turn off? 3. List out in some fashion what you want to happen when the tank is 1/3 full? A. Does the sensor give 9.3 ma or 14.7 ma? B. What valves will be opened, what will be closed? C. What motors will turn on and which will turn off? 4. List out in some fashion what you want to happen when the tank is 2/3 full? A. Does the sensor give 9.3 ma or 14.7 ma? B. What valves will be opened, what will be closed? C. What motors will turn on and which will turn off? THis should give you the bulk of the program you have to write in plain language, then the next step is to convert it to PLC logic. ALso check out the manual for the PLC Analog card http://literature.rockwellautomation.com/i...um002_-en-p.pdf It even ahs some drawings you might find useful. Hope this helps to start things off. Most all of us here will be glad to review any code your write as our time permits.

[Rod_Hackney 2]

I would take a look at the ultrasonic application and make sure you have it configured for the correct tank dimensions. If it is a cylindrical tank with a flat bottom, little setup should be needed but if bottom is angular in shape, you will need to take that into consideration with the configuration of the transmitter. Most ultrasonic transmitters allow for taking this into consideration but the actual way they input the calibration data varies widely. Your vendor should be able to provide assistance, if needed.

[pabeader 0]

yall might be overthinking this a little. all the OP asked was how to use Analog Card. I bet the rest of the post was for General information on working with Analog cards. I might be wrong. It did happen once a long time ago :)

[The Turkey Slayer 5]

Analog programming is quite simple. Analog input values are represented in the PLC by a range of integers, usually somewhere from 0 to 32767 or 0 to 16384. You need to refer to the manual of your analog module to find out what range of numbers correspond to the voltage or amp analog signal coming into the card. The 1769-IF4 card you're using uses a 4-20mA input signal. In the program, the Raw Data is represented by a range of the numbers 6241 (4mA) to 31206 (20mA) in it's corresponding input. So if your card is in "Slot" 2 and the ultrasonic sensor is in the first input, you will see the raw data number at I:2.0, the next sensor on the second input will be I:2.1, and so on. If it's in Slot 3, the inputs will be I:3.x and so on If your sensor is properly configured, it will read 4mA with an empty tank, and 20mA with a full tank, or 6241 empty and 31206 full. Of course, these numbers are meaningless in a real application, so you need to use the SCP (Scale with Parameters) Statement. It will first ask you for your raw input, which will be the I:x.x address, then the "Input Min" and "Input Max", which will be 6241 and 31206 respectively. The next three parameters will be the scaled min, scaled max, and output you would like to store this number in. Let's say your tank is 5000mm tall, so you would want enter 0 and 5000 in the scaled min and max, respectively. Then for your output, choose an unused F8 or N7 address, and you will have the actual level of the tank. For full and empty warnings, use compare statements like EQ, LEQ, or GEQ to turn on warning bits. Hope this helps.

[308 0]

pabeader, u read my mind. :) thanks turkey slayer man, u've actually helped a lot. i appreciate it. i really do. i'll keep bugging u guys if i get stucked on the way. thank u all Edited 27 Jul 2007 by 308

[Bob O 8]

all the OP asked was how to use Analog Card. I wouldn't be too sure about that one......:) What should I do and how do I write the program to meet the application needs?

[pabeader 0]

sometimes we ask more then we want. i do it all the time and can usually spot it in others