Hello,
I need to control an Acid pump at a water treatment plant, Using an analogue output of a micrologix 1400. This PLC only has 0-10V analogue output card. So I installed a 500Ohm resister across the pair of my instrument cables, to get my 4-20Ma. So at 2Votls will be my 4mA and 10 Volts will be 20mA.
PLC Resolution (0-4095)
Acid pump 1
0-60 L/H
Acid pump 2
0-12000 strokes per hour
In The PLC. I'm using RXLogix micro developer, and I'm using the SCP instruction to scale
I tried using one SCP block, but the input number that is entered is much lower than what is display in the pump
Example:
F8:1
input: F8:1 --->> entered 7 l/h in the HMI
input min: 0
input MAX: 60
scale min: 819
Scale max: 4095
Output O:0/0 --->> Pump said about 12 l/h
I tried using two SCP block per pump, to scale input number from the HMI to 4-20 and the second would scale the 4-20 to the PLC 12 bit analog card (4095)
but I got similar results...
SCP 1
Input: F8:1 ---->> entered 15l/h in the HMI
input min: 0
input MAX: 60
scale min: 4
scale max 20
Output F8:2 ---->> 8 mA
SCP2
Input: F8:2 ---->> 8 mA
Input min: 4
input max: 20
scale min: 819
scale max: 4095
Output: O:0/0 ----->> 1638
The results for example
today I entered 30 L/H in the HMI the pump said 41.8
for the other pump I entered 6000 strokes per hour, pump would say 12000 strokes per hour.
PLEASE HELP, if anyone has ideas....
Thanks everyone
I need to control an Acid pump at a water treatment plant, Using an analogue output of a micrologix 1400. This PLC only has 0-10V analogue output card. So I installed a 500Ohm resister across the pair of my instrument cables, to get my 4-20Ma. So at 2Votls will be my 4mA and 10 Volts will be 20mA.
PLC Resolution (0-4095)
Acid pump 1
0-60 L/H
Acid pump 2
0-12000 strokes per hour
In The PLC. I'm using RXLogix micro developer, and I'm using the SCP instruction to scale
I tried using one SCP block, but the input number that is entered is much lower than what is display in the pump
Example:
F8:1
input: F8:1 --->> entered 7 l/h in the HMI
input min: 0
input MAX: 60
scale min: 819
Scale max: 4095
Output O:0/0 --->> Pump said about 12 l/h
I tried using two SCP block per pump, to scale input number from the HMI to 4-20 and the second would scale the 4-20 to the PLC 12 bit analog card (4095)
but I got similar results...
SCP 1
Input: F8:1 ---->> entered 15l/h in the HMI
input min: 0
input MAX: 60
scale min: 4
scale max 20
Output F8:2 ---->> 8 mA
SCP2
Input: F8:2 ---->> 8 mA
Input min: 4
input max: 20
scale min: 819
scale max: 4095
Output: O:0/0 ----->> 1638
The results for example
today I entered 30 L/H in the HMI the pump said 41.8
for the other pump I entered 6000 strokes per hour, pump would say 12000 strokes per hour.
PLEASE HELP, if anyone has ideas....
Thanks everyone
Last edited: