bambinorama
Member
Guys
This is not a strictly PLC question, but I figure we deal with a lot of sensors input signal so I think this would be a good place to ask.
I have a wind direction sensor with 4-20mA output. So 0deg = 4 mA, 360deg = 20mA.
When the wind sensor turns anticlockwise from 5deg to 355deg without going through 10deg, 90deg, 250deg, 300 deg... (happens only when the wind sensor turns clockwise):
I expect quantums reading from 4.6mA to 18mA like this:
4.6mA
18mA
But then i see something like this:
4.6mA
12mA (transition reading a flicker of about 0.2 second)
18mA
The PLC picks up the 12mA reading and gives a false impression of the wind sensor turning clockwise going through 170deg.
So, I tested all 4-20mA output wind sensor types and they behave the same way, so i am thinking that all 4-20mA signal module has a variable potmeter inside (or some old classical analog transistor inside) and the signal cannot quantum jump from 4 to 20mA, but need a very brief transition say 12mA like this 4mA,12mA, 20mA.
Am I correct?!
If yes, does 0-5V behave the same way?? It must behave the same way, right?
This is not a strictly PLC question, but I figure we deal with a lot of sensors input signal so I think this would be a good place to ask.
I have a wind direction sensor with 4-20mA output. So 0deg = 4 mA, 360deg = 20mA.
When the wind sensor turns anticlockwise from 5deg to 355deg without going through 10deg, 90deg, 250deg, 300 deg... (happens only when the wind sensor turns clockwise):
I expect quantums reading from 4.6mA to 18mA like this:
4.6mA
18mA
But then i see something like this:
4.6mA
12mA (transition reading a flicker of about 0.2 second)
18mA
The PLC picks up the 12mA reading and gives a false impression of the wind sensor turning clockwise going through 170deg.
So, I tested all 4-20mA output wind sensor types and they behave the same way, so i am thinking that all 4-20mA signal module has a variable potmeter inside (or some old classical analog transistor inside) and the signal cannot quantum jump from 4 to 20mA, but need a very brief transition say 12mA like this 4mA,12mA, 20mA.
Am I correct?!
If yes, does 0-5V behave the same way?? It must behave the same way, right?