HSC - any advantage using A/B pulse?

Hi!
I use a s7-1200 with a HSC single phase on input i0.0 100kHz, and input filter set to lowest 0,1uS. It is around 1300pulses on each step we use. On a micrologix 1400 we have the same setup but are using A and B pulse. Here we get 5500 pulses per step. Micrologix also seem to have 100kHz inputs. The only diffrence is that on the Micrologix we use A and B pulse. Is this the explanation?
/Tim

With a single phase input you have no direction signal so if your encoder happens to stop on an edge you may get counts due to vibration.

you should get x4, so maybe someone has mistyped 5200?
The keys are right next to each other on the numpad.

It seems you have setup the S7-1200 to only count with 1 channel.
S7-1200 can also be setup for A/B counting. Definitely go for A/B counting if possible.

JesperMP said:

It seems you have setup the S7-1200 to only count with 1 channel.
S7-1200 can also be setup for A/B counting. Definitely go for A/B counting if possible.

Click to expand...

Yes I only use 1 channel. Why is it better with two channel? The accuracy is enough with 1 channel.

AustralIan said:

you should get x4, so maybe someone has mistyped 5200?
The keys are right next to each other on the numpad.

Click to expand...

When should I get x4? I know for a fact that the two diffrent PLCs work and position correct

Hi Tim,

When using A and B pulses you can evaluate rising and falling edges of both the A and B phase.

Deppending on whether your HSC is setup to evaluate only rising or falling edge of your 1 phase input, using both A and B phases will give you 4 times the resolution. If your current setup evaluates both rising and falling edges, you can only double the resolution.

The reason that AustralIan is thinking there is a typo in your first post, is that 1300 x 4 = 5200 and not 5500.

Also another advantage of using both A/B phases is that you can determine the direction in which the encoder is turning, and hence check for wrong wirring on either the encoder or motor terminals.

The 2 phases are offset from eachother

A __|""|__|""|__|""|__
B"|__|""|__|""|__|""|__

So if your A pulse is high and you get a rising edge B pulse, you know that the pattern is read from left to right.
If your B pulse is high and you get a rising edge A pulse, you know that the pattern is read from right to left.

That is the advantages of A/B phases compared to a single phase encoder.

Ok I see, then I get what you mean. I was just taking the pulses from my remembering so it can be 5200 pulses I just knew it was over 5000.

So if I'm ok with the accuracy as it is and is only using the pulses in one direction, then it isn't any major advantage to add the B pulse also?