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Flow Meter Unit: Understanding Volumetric and Mass Display Increments
Quick Answer
Volumetric increments on a flow meter display totalised volume in units like litre, cubic metre, or gallon. Mass increments show totalised mass in kilogram, tonne, or pound. Both depend on the meter type, the engineering unit set in the transmitter, and whether the meter measures volume directly or calculates mass from density. Choose the increment that matches your custody transfer ticket, batch log, or local trade regulation.
What "Display Increment" Means on a Silver Instruments Flow Meter
Every Silver Instruments flow transmitter includes a totaliser function. The totaliser runs continuously in the background and shows accumulated flow as a decimal number on the LCD or through the 4-20 mA HART output. The increment is the smallest digit that the display can show or log. For a volumetric totaliser, increments are typically 0.01 L, 0.001 m³, or 0.1 US gallon. For mass totalisers, typical increments are 0.001 kg, 0.0001 t, or 0.01 lb. These values are not arbitrary. They come from the meter’s resolution class and the full scale range you selected during commissioning.
We have seen many sites where an incorrect increment setting creates a mismatch between the flow computer and the PLC. A water treatment plant in Indonesia once logged 0.1 m³ increments on an electromagnetic flow meter, but the SCADA expected 0.01 m³ resolution. The result was a 10x scaling error that took two days to find. After setting the totaliser increment to match the pulse output weight, the values matched exactly.
Volumetric Display Increments: Electromagnetic, Ultrasonic, Oval Gear, and Vortex Meters
Volumetric flow meters measure fluid volume directly. The display increment represents a fixed volume of liquid or gas that has passed through the meter. For a DN25 electromagnetic flow meter on a demineralised water line, the factory default is often 0.01 L per pulse or per count. That gives a totaliser reading like 1254.32 L. On a DN200 ultrasonic flow meter for river water in Peru, a typical increment is 0.1 m³, so the display reads 2356.1 m³. Oval gear flow meters for diesel fuel in a Ghanaian depot usually use a 0.001 L increment for small DN4 meters and 0.1 L for DN25 meters. Vortex meters on saturated steam at 10 bar show volumetric increments in m³, but engineers often prefer mass due to steam density changes. Still, a volumetric increment of 1 m³ per count is common for a DN80 vortex meter.
When you order, tell us your required minimum measurable volume per batch. We then set the increment in the converter before shipment. Silver Instruments electromagnetic flow meters with LT03 converters allow you to set totaliser resolution from 0.001 L to 1000 m³, depending on DN size. Ultrasonic clamp-on meters with TUF converter support increments as low as 0.001 m³ for liquids. Oval gear meters with OG-LCD displays ship with a fixed increment based on gear volume per revolution. You can still change the engineering unit on site, for example from litre to US gallon. The increment automatically recalculates. One Caribbean fuel distributor switched from litre to US gallon after a firmware update and kept the same 0.1 gallon increment without re-scaling the pulse output. Test runs confirmed accuracy within ±0.2%.
Mass Display Increments: Coriolis and Thermal Mass Flow Meters
Mass flow meters measure mass directly or calculate it from a known density. Coriolis mass flow meters from Silver Instruments, like the CMF series, handle both mass and volume on the same transmitter. The default factory increment for mass totalisation is 0.001 kg on a DN10 sensor for chemical additives. For a DN50 sensor on crude palm oil in Malaysia, we often set 0.1 kg or 0.001 t. The meter can display both mass increment and independent volume increment simultaneously, because the CMF measures density and mass in real time. The volume increment then derives from the mass divided by density at line conditions.
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Thermal mass flow meters, like our TMF series for compressed air and biogas, always totalise in mass or standard volume. Display increments for mass are typically 0.01 kg or 0.001 kg for small pipe sizes. For a DN100 meter on biomethane at 30°C and 2 bar, we set 0.1 kg. This matches the typical hourly consumption of 150 to 400 kg/h that a packaging plant in Mexico reported. The display increments step by 0.1 kg, and the 4-20 mA output scales to 0-500 kg/h. Both agree perfectly.
How We Set the Increment at the Factory and What You Can Change in the Field
Every Silver Instruments flow meter leaves our Nanjing calibration station with a default engineering unit and increment set according to the order. If you gave us flow range, fluid type, temperature, and pipe size, we match the increment to your batch requirement. If not, we use a standard increment based on DN size and meter type. You can change later via the keypad, HART handheld, or Modbus RTU. The parameter name varies: on LT03 converters it is "Totl Unit" and "Totl Resol". On CMF Coriolis transmitters, it is under the "Totalizer" menu, submenu "Mass Inc" and "Vol Inc".
Because some SCADA and flow computers count pulses instead of reading the digital totaliser, we also configure the pulse output weight. The pulse weight must be an integer multiple of the display increment to avoid rounding errors. A desalination plant in Saudi Arabia used a pulse output of 0.1 m³ per pulse and a display increment of 0.01 m³. The PLC accumulated pulses and showed a total that drifted 0.3% per day from the local display. After setting the pulse weight to 0.1 m³ and display increment to 0.1 m³, the numbers matched.
Increment and Local Trade Regulations in Key Markets
In Ghana and Nigeria, diesel and petrol custody transfer often require litres with 0.1 L resolution on oval gear meters. In Indonesia, water PDAMs require m³ with 0.01 m³ increment on electromagnetic meters. Australian LNG and compressed natural gas users trading in kg demand 0.01 kg mass increment on Coriolis meters. In Colombia, palm oil mills prefer mass in kg with 0.1 kg resolution. We have shipped meters to all these regions with the local increment preconfigured. Ask your local weights and measures inspector what increment is required for your trade certificate. Send us the specification together with your flow range, temperature, and pressure, and we lock the totaliser accordingly. The physical seal on the converter prevents unauthorised changes.
FAQ
Can one flow meter display both volume and mass increments? Yes. Coriolis meters and some vortex meters with integrated pressure and temperature compensation can show two independent totalisers on the same screen. Each has its own increment setting.
Does changing the unit from m³ to litre change the totaliser value? The totaliser resets to zero when you change the engineering unit on most Silver Instruments transmitters. Export the totaliser value via Modbus before making the switch.
What is the smallest mass increment available on a Silver Instruments Coriolis meter? 0.001 kg on DN10 and smaller sensors. Contact [email protected] with your fluid and density for an exact figure.
Why does the display increment not match my pulse output total? Usually because the pulse weight and display increment use different measurement units or resolutions. Set both to the same value and test with a known volume or mass.
Can you preconfigure the increment for my specific batch process? Yes. Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range. We ship the meter with the correct increment and pulse output. Tel: +86-25-68650347, Whatsapp: +86-25-52155837, WeChat: +86 15365082610.