Troubleshoot USB Power Noise Causing Pressure Reading Drift on a Ralston Gauge

Troubleshoot USB Power Noise Causing Pressure Reading Drift on a Ralston Gauge

Problem

Unexpected pressure reading changes on an Ralston LC gauge when connected via USB.  

Root Cause

Electrical noise is introduced through a low-quality USB hub and power supply interference. 

  • Noise from switch-mode power supplies (SMPS) can travel through the AC mains, into the PC, through the USB cable, and finally to the gauge’s ground reference.

  • This noise introduces spurious voltages into the sensor circuit ground, resulting in a false pressure offset.

Recommended Actions

  1.  Always use the recommended Ralston model D-000410.  

  2. Avoid using low-quality or unpowered USB hubs. Connect directly to the PC whenever possible.

  3. Use a single, grounded AC circuit dedicated to test and measurement devices.

  4. Inspect external power supplies for noise or instability, replacing those that are failing or unshielded.

  5. Minimize shared connections between high-frequency devices (e.g., routers, chargers) and test instruments.

  6. If electrical noise persists, consider using a USB isolator or a filtered power source.

    • Related Articles

    • Calibrate the pressure sensor on a Field Gauge and Process Meter

      Do-it-yourself instructions for calibrating a Ralston digital gauge with the free FieldLab Desktop software. At the end of this process, FieldLab Desktop will automatically make any necessary adjustments to bring your Ralston gauge to acceptable ...

    • Adjust Power Settings on a Field Gauge

      Adjust settings for: Backlight Brightness, Backlight Auto Off , Auto Power Off Backlight The backlight on a Field Gauge makes it easier to read the information on the display when it is on. Because the backlight draws more power from the AA batteries ...

    • Adjust Power Settings on a Field Gauge LC20

      Adjust settings for: Backlight Brightness, Backlight Auto Off , Auto Power Off Backlight The backlight on a Field Gauge makes it easier to read the information on the display when it is on. Because the backlight draws more power from the AA batteries ...

    • Quick-Start Guide and User Manual for Field Gauge LC10

      Download in PDF format below.

    • Determine the max pressure for your Ralston gauge.

      Before applying pressure to your Ralston gauge, confirm that the gauge is rated for higher than the max pressure that will be applied. Gauges that have been overpressured above 33% of max rating will be unable to display or log accurate pressure ...

    • Recent Articles

    • Troubleshoot USB Power Noise Causing Pressure Reading Drift on a Ralston Gauge

      Problem Unexpected pressure reading changes on an Ralston LC gauge when connected via USB. Root Cause Electrical noise is introduced through a low-quality USB hub and power supply interference. Noise from switch-mode power supplies (SMPS) can travel ...

    • Adjust Damping on your Ralston Gauge

      Damping slows the visual updates of a pressure gauge’s reading. The goal is to minimize minor fluctuations of the pressure reading on the screen caused by subtle variations in pressure that may create unwanted visual noise. Ralston gauges are set to ...

    • Register your Ralston Gauge

      Register your Ralston gauge to access calibration certificates and install firmware updates. This article applies to: FieldLab, Field Gauge LC10, LC20, and Process Meter LC30, all models. Things you will need: A PC running Windows. FieldLab Desktop ...

    • Look Up Lead Time and Pricing for a Ralston Product

      Go to ralstoninst.com Sign in to your Ralston account Select "Look Up Pricing and Lead Time by Model Number" Enter the model number of the Ralston product View the search results For each model number in your search results, info will be provided ...

    • Download Current Price List

      Get current pricing for all Ralston products Price lists are available in PDF, XLS, and CSV formats. All file formats include the following fields: Product Family (e.g. "NPT Male Quick-test Adapters) Part Number (e.g. "QTHA-2MS1") Description MSRP ...