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Connecting a Flow Meter to LOGO! PLC

You're on the right track using a counter! LOGO! doesn't have a direct "comparator" block, but we can achieve the comparison using network outputs and logic.

Programming Steps:

1. Counter Block: Use a counter block (e.g., C1). Configure it to count pulses from your flow meter's input (I1). Set the counter's preset value to 100.
2. Counter Output (Q): The counter's output 'Q' goes HIGH when it reaches 100 pulses.
3. RAM Memory: Utilize a RAM memory (M1-M12) to store the '1 Liter' status.
4. Logic for Comparison & RAM Update: Connect the counter's 'Q' output to a network. Within this network:
   • Use a 'Set' coil to set the RAM memory bit (e.g., M1) HIGH when the counter 'Q' is HIGH. This indicates 1 Liter has flowed.
   • Use a 'Reset' coil connected to the same RAM memory bit (M1), triggered by a separate input or timer if you need to reset the '1 Liter' indication.
5. Output: Use the RAM memory bit (M1) to drive an output (Qx) to signal a completed liter.

Example Network:

I1 (Flow Meter Pulse) --> C1 (Counter, Preset=100)

C1.Q --> Set M1 (RAM Memory)

M1 --> Qx (Output - 1 Liter)

Important Resources:

• LOGO! 8 - How to use counters
• LOGO! 8 - RAM memory

For detailed programming guidance and to download the LOGO!Soft Comfort software, please visit the Siemens LOGO! webpage.

Calculating Flow Rate with a Hall Effect Flow Sensor and LOGO! PLC

You're on the right track using the high-speed counter input of the LOGO! PLC with your Hall effect flow sensor. Calculating flow rate requires converting pulse frequency to a flow rate unit (e.g., liters per minute, gallons per hour).

Here's the approach:

1. Determine Pulses per Unit Volume: This is critical. Your sensor's datasheet will specify how many pulses are generated per unit of fluid volume (e.g., 1 pulse per liter). Let's call this 'K'.
2. Measure Pulse Frequency: The LOGO! PLC's high-speed counter will give you the number of pulses over a specific time.
3. Calculate Volume: Volume = (Pulse Count / K). This gives you the volume that has passed during the counting period.
4. Calculate Flow Rate: Flow Rate = Volume / Time Interval. For example, if you count pulses over 1 second, the resulting volume is your flow rate per second. Convert to desired units (e.g., multiply by 60 for liters per minute).

LOGO! Programming:

• Use a high-speed counter block in your LOGO! program to count the pulses from the sensor.
• Configure a timer to define the time interval for your flow rate calculation (e.g., 1 second).
• Use mathematical blocks to perform the calculations described above.
• Display the calculated flow rate on a LOGO! display or transmit it via network.

Resources:

• Siemens Industry Online Support - LOGO!
• Refer to your flow sensor's datasheet for the 'K' factor.

Important Note: Ensure proper scaling and units in your LOGO! program to obtain accurate flow rate readings.