RotoFlow -155421 Paddle Wheel Flow Meter - Atlas Scientific

AtlasScientific 

Biology • Technology 

RotoFlow -155421 

Paddle Wheel 

Flow Meter 

Features 

• Ultra high accuracy Flow Meter 

• Paddle Wheel sensing unit 

• See through front panel for visual inspection 

• Minimum flow rate 378 ML / min 

• Maximum flow rate 20 L / min 

• Max operating pressure (40 psi) 275 kpa 

• Operating temperature 

(-20º F to 180º F) -29º C to 82º C 

• Max viscosity 200 ssu 

• Materials 

Body: Polypropylene 

Rotor Pin: Ceramic 

Paddle Wheel: Polypropylene Sulfide 

Front Panel: Polysulfone 

O-ring: Buna-N 

• Food safe 

• Diesel safe 

• Kerosene safe 

• Gasoline safe 

• 3 lead cable (35”) 88.9cm long 

Atlas-Scientific.com 

Copyright © Atlas Scientific LLC All Rights Reserved 

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Description 

The RotoFlow-155421 Paddel Wheel Flow Meter is an extremely accurate flow meter of 

moderate complexity. This flow meter requires specific timing and calculations to provide 

meaningful data. All of which is described in this datasheet. 

The RotoFlow-155421 provides the user with extremely reliable readings for flow rates from 

378 ml/min (0.1gpm) up to 75.7 L / min (20 gpm). 

Wiring 

The RotoFlow-155421 Flow Meter has an 71.1 (28”) 

cable that terminates with three tinned leads. 

PULSE 


VCC 

GND 

Lead Color Function 

BLACK GND 

RED 

VCC 3V to 24V 

White PULSE 



PULSE 

Microcontroller 

REVERSING THE POLARITY WILL 

DESTROY THE FLOW METER 

GND 


VCC 

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Pre-filter Requirements 



It is strongly recommended to use a pre-filter of at least 50 microns. Atlas Scientific has 

performed many tests on the RotoFlow-155421 Flow Meter and has concluded that 

reliable operation is not possible without one. The paddle wheel blades can easily 

become jammed with small particles that will (generally speaking) not damage the device, 

nor stop water flow; however the RotoFlow-155421 will no longer be accurate. To restore 

accuracy run water backwards through the RotoFlow-155421 until all the debris has been 

cleared. 

Data Output 

The White lead from the RotoFlow-155421 will output flow data in Hz from 0 to 200+ Hz. 

The RotoFlow-155421 Flow Meter does not simply convert pulses to volume. The pulse 

is only one part of the equation and cannot alone give meaningful flow data. 

EVENT EVENT 


A pulse from the RotoFlow-155421 

is a rising edge, followed by a falling edge. 


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Best Practices for Data Interpretation 

using a Microcontroller 

The RotoFlow-155421 Flow Meter is relatively simple to interface with any microcontroller. 

Reading the frequency output from the RotoFlow-155421 should be done in one of two 

ways. [ISR method or Counter method] 

DO NOT POLL THE PIN DIRECTLY, THIS WILL RESULT IN INACCURACY 

ISR Method 

Connect the pulse out lead (white) to an external interrupt pin on your microcontroller. 

Set the interrupt pin to be triggered on a rising edge. Create an ISR (interrupt Service 

Routine) in your code that ONLY incurs a variable. 

ISR(void) { 

pulse_count +=1; 

} 

Use a section in your main code to poll the variable pulse_count and 

to do the necessary math 

main(void){ 

while(1){ 

if (pulse_count){ 

total_flow+=pulse_count; 

pulse_count=0; 

} 

} 

Counter Method 

Enable the timer/counter on your microcontroller, and set it to counter mode. It is 

advised that you use a 16 bit or larger counter. The counter will have an internal registry 

variable that will count the pulses. How you then read and interpret that registry value is 

for you to decide. 



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Data Interpretation 

To turn the pulses into flow rate you must obtain the pulses per minute. It is imperative 

that your microcontroller has a reliable clock source that is capable of interrupting every 

one second. Using R.T.C. is not advised, unless the R.T.C. can interrupt your 

microcontroller every one second. 

A better option is to simply connect a 32.768 KHz crystal to the timer/counter of your 

microcontroller and use that to interupt every one second. 

Count the pulses that your microcontroller receives each second. After 15 seconds add 

up all the pulses received and multiply that by four. 

Example 

After 15 seconds the microcontroller has detected 25 pulses. 

25 x 4 = 100 

This is a simple way of deriving pulses per minuet without having to wait a whole minute 

before knowing the time pulses per minuet. 

(15 seconds x 4 = 60 seconds) 

Assuming that we stored the number of pulses in the variable “pulses_per_min” the 

following code shows how to derive pluses per minute to volume and volume per 

minute. 

pulses_per_min * = 4; //multipliying the pluses times four 

volume=0.6662338572e-2 + 0.1666328970e-2 * pulses_per_min; 

flow_rate=(volume*60); 




Atlas Scientific has determined these equations to be accurate 

in reading volume and flow rate for the RotoFlow-155421. 


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RotoFlow -155421 Paddle Wheel Flow Meter - Atlas Scientific

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