Setting Up a Precision Digital Liquid Level Control System

Benefits of This System

  • Programmable set-points and alarms
  • Display of the current level, including programmable units
  • Incredibly simple installation

What We'll Need

  • Precision Digital Process Meter & Controller, with relay outputs and transmitter power (or a separate 24v power supply for the sensor). We'll be using a PD6000 ProVu with two relays
  • Submersible level transmitter. We will use the Ametek model SDT level transmitter with 4-20mA output. However, there are many other sensor options such as ultrasonic or continuous level floats with 4-20mA output that would also work.
  • Enclosure with 1/8 DIN cutout
  • Pump contactor. The relays in this controller are too small to switch a pump directly, so we need to use an external contactor. In this case, we are using a B/W Controls 1500 Series relay to switch the current.
  • Phillips screwdriver
  • Small slotted screwdriver
  • Wire stripper
  • Wire for controls and pump

Mounting

Mounting the controller in a housing is very simple. It fits in a standard 1/8 DIN cutout.

  1. Locate the mounting brackets on the sides of the unit.
  2. press these brackets firmly toward the front of the controller, and they will pop out
  3. Slide the meter into its cutout, and replace the brackets, pressing them back in the opposite way in which they were removed. They should snap back into place.
  4. Tighten the mounting screws until the meter is snug; however, do not over-tighten.

Installation

Install the sensor in the tank according to its specifications. In this case, to install the sensor, we simply place it at the bottom of the tank. For a real installation, we would probably want to secure the cable to the top of the tank.

Wiring

  1. Provide power to the controller. Connect the two power leads to the power contacts on the controller. Polarity does not matter for this meter
  2. Connect the 4-20mA hydrostatic sensor to the controller. To do so, remove the sensor terminal block from the controller, and make the connections. In this case, we will:
    • Jumper the COM and P- terminals
    • connect the red wire to P+
    • Connect the green to COM
    • Connect the black to the mA+ terminal
  3. Connect the pump contactor to the connector block. To do so, select a relay on the controller. In this case, we will be using Relay 1.
    • Connect the contacts on the relay to switch the current to the contactor. For most contactors, this would be wired inline with the power to the coil.
    • For most pump-up or pump-down configurations, use the N.O. (normally-open) terminal. For certain applications, the N.C. (normally-closed terminal may be more practical; however, in this case, we will use the N.O. terminal.

Programming the Controller

We can program the controller either from the front panel, or from a computer via the USB port.

Programming from the Front Panel

  1. Power on the controller. It will initialize, and then read out the raw mA signal. If it does not show the raw mA signal, check the connections.
  2. Make a note of the mA reading as well as the number of gallons or level in the tank. We will use this for scaling the reading later.
  3. Press the Menu button to enter Programming Mode.
  4. Press the Enter key to select Setup.
  5. Press the Enter key again.
  6. Use the Up arrow key to select an input type. In this case, we will press the Enter key to select mA input.
  7. Press the Enter key again.
  8. Use the Up arrow to choose Yes or No for Dual-Scale functionality. In this case, we will select No.
  9. Press Enter again to select Units configuration.
    • Enter the display units. Scroll through characters with the up arrow and move to the next digit with the Right Arrow key.
    • In this case, we will label our units as gallons.
    • Press Enter to confirm the unit selection
  10. Press enter to choose the decimal point placement for display.
    • Use the Right Arrow to move the decimal point, and Enter to select it.
  11. Press Enter to set the display scale for the meter.
    • Input the mA reading corresponding to an empty tank, and press Enter.
    • Press Enter again to set the display reading for that input value.
    • Input the display reading, and press Enter.
    • Input the mA reading for the current tank level that we recorded earlier, and press Enter.
    • Press Enter again to set the display reading for that input value.
    • Input the display reading. In this case, we have 4 gallons in the tank. Press Enter.
  12. Press the up arrow and Enter to set Relay configuration
    • Press Enter to configure Relay 1.
    • Use the Up Arrow key to select a Relay Action. In this case, we will merely press Enter to select Automatic Reset.
    • Press Enter, and input the relay Set Point. This is where the pump will turn on. We will have the pump turn on when the level drops below 4.5 gallons.
    • Press Enter, and input the relay Reset Point. This is where the pump will turn off. We will have the pump turn off when the level reaches 5 gallons.

Programming via Software

Programming can be done in fewer steps using the included MeterView Pro software.

  1. Plug the meter in to a Windows computer via the included Micro USB cable. A file explorer window will pop up.
  2. Double click on "MAStart" and follow the instructions to install the MeterView software. Be sure to "Allow" the program to make changes when prompted.
  3. When the installation is finished, check the box to launch MeterView Pro, and close the window.
  4. You should now see the MeterView Pro software open, with your meter type displayed. In this case, it shows PD6000.
  5. Click the "Configure" button.
  6. Choose your units to be displayed on the meter. In this case, we will type GAL for gallons.
  7. Click the "Programming" tab at the top of the software.
    • Here we will configure the display scale for our units. In this case, 4 mA, the low end of our scale, will correspond to zero gallons of water in the tank.
    • Similarly, we saw earlier that it read 5.15 mA with 4 gallons of water in the tank.
    • Next, choose the position for the decimal point. We will leave it at 3 digits of precision.
  8. Next, click the "Relays" tab. Here we will configure the action of the on-board relays.
    • In this case, we will leave the action at "Automatic."
    • Next, choose a set point. This will be where the relay turns on. We will set it to turn on when the water level reaches 4.5 gallons.
    • Next, choose a reset point. This will be where the relay turns off. We will set it to turn off when the water level reaches 5 gallons.
    • Since our set point is below our reset point, we have this relay configured for pump-up. For pump-down control, the set point should be above the reset point.
  9. There are many additional settings available, but we are now finished programming the controller for our application. Click "Send Meter Data" to write the configuration to the controller, then Exit the program.
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