Getting two (or more) pulses per dial rotation
Posted: Sun Jun 18, 2017 12:14 pm
I have a new EKM 3/4" water meter (SPWM-075) which I'm connecting to an Arduino, and I'm trying to figure out the pulse output.
It seems like each rotation of the 0.1 cu. ft. dial generates at least two pulses: a short pulse lasting ~5% of the rotation, then a gap of ~2%, then a longer pulse lasting 45% of the dial rotation. Sometimes the long pulse also has a very brief gap (~0.2%) about 5% of the cycle into it.
[EDIT: this turned out to be a bad multimeter -- not a problem with the water meter.]
Here's a picture of the pulses from two dial rotations (at a flow of ~43 cu. ft./hr): Two questions:
1. Is this normal? I understand reed switches can be bouncy, but the gaps are well after the initial closure of the contacts.
2. Any suggestions for getting an accurate pulse count from this? I'm having trouble figuring out how to reliably ignore the short pulses or the gaps.
This is for a multi-zone irrigation system, so the flow rate won't be constant. At 5GPM, the short pulses are half a second long, and the gaps 0.15s. Also, it would be relatively easy for the water to shut off in the middle of a short pulse. (All of the de-bouncing approaches I can think of would get confused by that.)
Thanks for any info and assistance.
Mike
P.S., Here's an audio recording of my continuity meter hooked up to the water meter pulse output, covering several more rotations of the dial. The extra pulses and gaps are really easy to hear.
It seems like each rotation of the 0.1 cu. ft. dial generates at least two pulses: a short pulse lasting ~5% of the rotation, then a gap of ~2%, then a longer pulse lasting 45% of the dial rotation. Sometimes the long pulse also has a very brief gap (~0.2%) about 5% of the cycle into it.
[EDIT: this turned out to be a bad multimeter -- not a problem with the water meter.]
Here's a picture of the pulses from two dial rotations (at a flow of ~43 cu. ft./hr): Two questions:
1. Is this normal? I understand reed switches can be bouncy, but the gaps are well after the initial closure of the contacts.
2. Any suggestions for getting an accurate pulse count from this? I'm having trouble figuring out how to reliably ignore the short pulses or the gaps.
This is for a multi-zone irrigation system, so the flow rate won't be constant. At 5GPM, the short pulses are half a second long, and the gaps 0.15s. Also, it would be relatively easy for the water to shut off in the middle of a short pulse. (All of the de-bouncing approaches I can think of would get confused by that.)
Thanks for any info and assistance.
Mike
P.S., Here's an audio recording of my continuity meter hooked up to the water meter pulse output, covering several more rotations of the dial. The extra pulses and gaps are really easy to hear.