Studio 5000 totalizer

[Dodgers818]

Good morning,

I have a flow meter that has an output pulse configured to 378.541 liters per pulse.

My question is, do I just count the pulse per hour and multiply by 378.541 to get liters per hour based on the number of pulses?

What about the K-factor of 1.1918 and its relevance?

Thank you in advance.

 

[cardosocea]

Each rising edge means that a pulse, an absolute quantity of volume, has went past your flowmeter. Unless you measure time, the pulse itself won't tell you anything about flow.



I count pulses, then multiply by the liter per pulse. The k factor is usually liters/pulse, which instrument are you using??

I also run a timer and whenever it lapses calculate the volume per minute, hour, whatever.

I have in the past used frequency input cards to give me flow... they worked ok actually.

 

[drbitboy]

378.541l = 100USgal.

This would be easier in traditional units.

To answer your question, yes, multiply the pulses per hour by 378.541l/pulse to get l/h.

TL;DR

if this equation

    1 pulse = 378.541 litre

is true, then we can divide both sides of that equation by [1 pulse]:

1 pulse   378.541 litre
------- = -------------
1 pulse     1 pulse

Since quantity divided by itself is 1, the left-hand side reduces to 1:

    378.541 litre           litre
1 = ------- ----- = 378.541 -----
      1     pulse           pulse

So that means that, in the context of that flowmeter, the quantity [378.541 litre/pulse] equals 1.

Since multiplication by 1 is the multiplicative identity operation, we can multiply an initial quantity by 1 and the result is equal to the initial quantity.

     pulse

1000 -----

     hour



       pulse   

= 1000 ----- * 1

       hour



       pulse           litre

= 1000 ----- * 378.541 -----

       hour            pulse



                 litre

= 1000 * 378.541 -----

                 hour



          litre

= 378,541 -----

          hour

 

To summarize, we are not multiplying by 378.541, we are multiplying by unity i.e. by one. In my experience, 80-90% of practical engineering boils down to multiplying by unity, and the only hard part is determining the context-dependent, applicable value of unity.

Kudos to you for intuitively figuring out the right answer; harsh criticism to your past teachers and mentors that this was not taught to the point that you knew it in your bones and didn't have to ask the question in the first place.

Nevertheless, welcome to the forum.

 

[Aardwizz]

In my experience, 80-90% of practical engineering boils down to multiplying by unity.

I am forever grateful to my high school Chemistry teacher who taught us to multiply by unity when doing unit conversions, and that the same unit in the numerator and denominator cancel out, just like numbers do.

So much easier than that "cross-multiply" stuff they tried to teach when adding fractions: just multiply both fractions by (different) unities so that the denominator winds up the same, then the two fractions are added easily.

The way they teach it, you'd think that teachers want children to hate maths.

 

[parky]

First of all, that unit can be set at 0.0001 ltrs per pulse to 1cm3 per pulse so the range you select is up to you the more pulses per unit of measurement (volume) the better the accuracy.
Also why try calculating the flowrate it also has am analogue output to give you flowrate so the maths is done for you.
So... Use pulse for volume amount i.e. perhaps usage or batch, analogue flow for instant flowrate.

 

[cardosocea]

First of all, that unit can be set at 0.0001 ltrs per pulse to 1cm3 per pulse so the range you select is up to you the more pulses per unit of measurement (volume) the better the accuracy.

The caveat being "If the input can read that fast"... I've been bit by that before to the point of having to be swapping rotors in the flowmeter. (to have less pickup magnets).

 

[parky]

Yes normally use high speed inputs or interrupts, but 300+ litres a pulse is way out I would think even based on 20ms scan time you would probably not need those sort of scaling for pulses. also, it has analogue why not use that for flowrate.

 

[OkiePC]

I recommend counting the pulses, and only convert to volume when and where you need to. Don't accumulate totals by adding real numbers together or you will lose precision.

For the rate, I measure the time between rising edges of consecutive pulses and calculate rate from that. It give you the most rapidly updated rate calculation but can also create a signal that varies a lot and the application may benefit from further filtering of the result. Also, when the flow stops, you need a time limit for how long do you wait to "call it zero".

The rate calculation is entirely separate from the total..

If you can, it is cleaner and simpler to set up the device to make each pulse a whole unit of measure or a nice round multiple (like times ten, for example).

 

[Dodgers818]

The meter i am using is a truflo MF 1000 series magnetic flow meter.

 

[Dodgers818]

First off, Thank you everyone for your responses. They are greatly appreciated.

 

[Dodgers818]

So my logic is:

1) counting pulses for one hour
2) multiplying the pulse counts by 378.541 = A (liters/hour)
3) multiply A (liters/hour) by 0.264172 = B (gallons/hour)
4) divide B (gallons/hour) by 1.1918 (meter K-factor) = gallons/hour totalizer

How does that look, correct?

 

[drbitboy]

So my logic is:

1) counting pulses for one hour
2) multiplying the pulse counts by 378.541 = A (liters/hour)
3) multiply A (liters/hour) by 0.264172 = B (gallons/hour)
4) divide B (gallons/hour) by 1.1918 (meter K-factor) = gallons/hour totalizer

How does that look, correct?

Steps 1 and 2 and 3 look correct, assuming that one pulse is indeed 100USgal and "gallons" means USgal (= 231in³).

Step 3 could be "multiply the pulse counts by 100 = B (USgallons/h), but only if you care out to the fifth significant digit.

For step 4, I am not sure what the "1.1918 (meter K-factor)" is or the difference between "gallons/h" and "gallons/h totalizer." 1.1918 is close to the number of US gallons in an Imperial gallon, but it is off by one part in ~130 (~three-quarters of a percent).

 

[Steve Bailey]

1) counting pulses for one hour

If you're after a rate, why wait an hour? You can calculate a rate from the time between pulses.

2) multiplying the pulse counts by 378.541 = A (liters/hour)

OK

3) multiply A (liters/hour) by 0.264172 = B (gallons/hour)

Or you could multiply the original pulse counts by 100 and eliminate any round-off error arising from the calculation of A and B.

4) divide B (gallons/hour) by 1.1918 (meter K-factor) = gallons/hour totalizer

Using the total pulses to calculate a rate and then using that rate to calculate a total is guaranteed to introduce errors.

 

[Dodgers818]

I am looking for totalizer result.

The meter has a parameter (setting) that can be configured: Pulse Value (L/p) 378.541.

I'm looking for a totalizer not flow rate.

 

[Dodgers818]

I don't know how to respond to individuals, but I do want to thank everyone for their responses. they are very helpful.

Thank you everyone!!!