The display screen of a liquid turbine flowmeter not lighting up could be caused by several factors. You can troubleshoot the issue by following these steps:

1. Power Supply Issues

• Check power connection: First, verify that the power supply is properly connected. If an external power source is used, inspect the power cable for any looseness or damage, and ensure the power plug is securely connected.
• Measure voltage: Use a multimeter to measure the power voltage and confirm that the supply voltage meets the flowmeter's requirements. If the voltage is too low or there’s no power, the display screen won’t function.
• Battery-powered devices (if applicable): If the flowmeter is battery-powered, check if the battery is depleted. Replace the battery if necessary.

2. Display Screen Malfunction

• Check for damage: Prolonged use or physical impact could damage the display screen. If there is visible physical damage or signs of wear, the screen may need to be replaced.
• Connection issues: Check the connection between the display screen and the main control circuit board to ensure that there are no loose wires or connectors.

3. Signal Transmission Issues

• Sensor malfunction: If the turbine flowmeter’s sensor is damaged or the signal transmission is unstable, the display might not light up. Check the sensor’s working condition and signal transmission. If faulty, the sensor may need to be replaced or repaired.
• Wiring inspection: Examine the internal signal wires for any disconnections or poor contact, which are common in harsh working environments.

4. Main Control Board or Circuit Issues

• Main control board malfunction: The main control board is responsible for processing sensor signals and driving the display. If the control board fails, the display will not function. You can check the indicators or signals on the control board to determine if it needs to be repaired or replaced.
• Aging components: If the flowmeter has been in use for many years, components such as capacitors may have aged, causing circuit issues and preventing the display from lighting up. Inspect the board for any burnt or aging components.

5. Software or Program Issues

• Reset or restart the device: Sometimes, software or program faults can cause the display screen to malfunction. Try resetting the device or restarting it after turning off the power.
• Check settings: If the flowmeter has parameter settings, ensure that the display settings have not been turned off or misconfigured, which could prevent the screen from showing.

By following these steps, you can systematically troubleshoot the issue with the liquid turbine flowmeter’s display. If the problem persists, it’s advisable to contact the manufacturer or a professional technician for further inspection and repair.