Plastic Paddle-Wheel Flow Transmitter – DPL

The KOBOLD DPL is an all-plastic low flow paddle-wheel sensor (a low volume rotating vane flow meter) designed for low cost, accurate measurement of water and other transparent liquids from 0.4 to 400 GPH. All wetted parts are synthetic, so the sensor resists aggressive media, and the compact body is designed for tight installations, including the interior of larger systems. It is suited to industrial, commercial, and laboratory flow applications and is made in the USA, with BABA (Build America, Buy America) compliant models available.

How the DPL paddle-wheel flow sensor works

A jet of liquid is directed at a free-running turbine inside a specially shaped chamber. As the turbine spins, its blade interrupts an internal infrared beam, and the electronics convert those interruptions into a pulse output with a frequency directly proportional to the flow rate. The vane runs on sapphire bearings for high linearity and long service life.

Nominal output frequency at maximum flow is 272, 471, 505, 265, and 399 Hz for the five measuring ranges.

DPL flow ranges, accuracy, and ratings

The DPL is offered in five measuring ranges: 0.4 to 8.0, 0.8 to 28, 3.0 to 95, 6.0 to 190, and 16 to 400 GPH. Accuracy is ± 2.5 % of full scale (± 5 % of full scale for the OEM version), linearity is ± 1 % of full scale, and the maximum pressure rating is 145 PSIG (10 bar).

Media temperature: -40 to 158 °F (-40 to 70 °C)
Ambient temperature: -22 to 140 °F (-30 to 60 °C)
Maximum differential pressure at full flow: 10 to 19 PSI, depending on range
Protection rating: IP 65

Materials, process connections, and dimensions

The housing and rotating vane are polypropylene (PP), the axle and bearings are sapphire, and the vane mount is polysulfone. Gaskets are NBR, FKM, or EPDM. Process connections are G ½ male thread or hose barbs for ½ inch PVC hose.

The body is 75 mm (2.95 in) long between connection ends with 24 mm (0.94 in) wrench flats.

DPL output, electronics, and wiring options

A pulse frequency output is standard on every DPL; a 4-20 mA analog output and a digital display are optional. Six electronics versions are available. M12x1 versions use pin 1 for +Vs, pin 3 for GND, and pin 4 for the signal.

..K000: frequency output, NPN open collector (max. 10 mA), 4.5 to 12 VDC supply, 5 ft 5-wire cable, OEM version without CE mark
..F300: frequency output, PNP open collector (max. 20 mA), 24 VDC ± 20 % supply at 40 to 50 mA, M12x1 plug
..L343: 4-20 mA 3-wire analog output, max. load 500 Ω, 24 VDC ± 20 % supply, M12x1 plug
..L443: 4-20 mA 3-wire analog output, max. load 500 Ω, 24 VDC ± 20 % supply, DIN 43 650 plug; accepts the optional AUF-3000 4-digit LED plug-on display, powered through the analog output
..C30R: compact electronics with 3-digit LED display and two PNP open collector switching outputs, M12x1 plug
..C34P: compact electronics with 3-digit LED display, 4-20 mA output, and one PNP open collector switching output, M12x1 plug

Compact electronics (..C3xx) run on 24 VDC ± 20 % at approximately 100 mA, 3-wire; switch contacts are programmable as normally open or normally closed and are set with two buttons. Mating connectors with 6 ft cable: part 807.037 (4-pin) for ..F300 and ..L343, part 807.007 (5-pin) for ..C30R and ..C34P.

Installing and maintaining the DPL

Install the DPL with flow in the direction of the arrow on the body; any mounting orientation is permitted. Support the inlet and outlet piping about 50 mm (2 in) from the connection joints, avoid pressure, tensile, or torsion loads on the joints, and allow a minimum straight run of 5 × DN upstream and 2 × DN downstream.

Do not exceed the measuring range: overranging the vane can damage the axle bearings and cause significant measurement errors. With clean media the instrument is maintenance-free, and an upstream filter is recommended. If cleaning is necessary, the sensor can be opened; take care not to damage the vane, and reinstall it in the correct position and direction. Electronics work is reserved for the manufacturer.

Ordering the DPL and specifying flow direction

Order codes follow the example DPL-1PU1 G4 K000: the letter after 1 selects the gasket (P for NBR, V for FKM, E for EPDM), U1 through U5 select the measuring range from smallest to largest, G4 is the G ½ male thread and S4 the ½ inch PVC hose barb, and the final code selects the electronics.

Models with compact electronics (..C30R and ..C34P) require the flow direction to be specified when ordering, read as if facing the meter (for example, vertical flow, bottom to top); orders that omit it may be delayed.

Common Questions about DPL - All-Plastic Low Flow Paddle-Wheel Sensor

The DPL is designed for water and other transparent liquids. Wetted parts are polypropylene, polysulfone, and sapphire, with NBR, FKM, or EPDM gaskets chosen by model code, which is why it tolerates aggressive media. Select the gasket material and the measuring range to match the liquid and the expected flow.

The smallest range starts at 0.4 GPH and runs to 8.0 GPH. Four more ranges extend coverage to 400 GPH. Choose the range that contains your maximum expected flow, because running above the top of the range can damage the sapphire axle bearings and degrade measurement.

The DPL is rated to 145 PSIG (10 bar). Liquid temperature can be -40 to 158 °F (-40 to 70 °C) and ambient temperature -22 to 140 °F (-30 to 60 °C). Pressure drop across the meter at full flow lies between 10 and 19 PSI across the five ranges.

Yes. Three versions provide a 4-20 mA signal: ..L343 with an M12x1 plug, ..L443 with a DIN 43 650 plug, and the compact ..C34P, which adds an LED display and a switching output. All three are 3-wire, operate from 24 VDC ± 20 %, and drive loads up to 500 Ω.

The ..F300, ..L343, ..L443, and compact ..C3xx versions use 24 VDC ± 20 %; the ..F300 draws 40 to 50 mA and the compact electronics about 100 mA. The OEM ..K000 version runs on 4.5 to 12 VDC at about 7 mA with an NPN open collector pulse output rated 10 mA maximum.

Yes, two ways. The ..C30R and ..C34P compact electronics include a 3-digit LED display with two setting buttons and switching outputs. The ..L443 analog version accepts the AUF-3000, a 4-digit LED plug-on display for the DIN 43 650 connector that takes its power from the analog output.

A minimum straight run of five pipe diameters upstream and two pipe diameters downstream is recommended. Fasten the inlet and outlet piping roughly 50 mm (2 in) away from each connection joint so the fittings carry no pressure, tensile, or torsion loads, and check the joints for leaks.

With clean media, yes. Installing a filter upstream is recommended to keep debris away from the vane. If cleaning becomes necessary, the housing opens for access to the internals; the vane must not be damaged and must go back in correctly, oriented the right way. Electronics repairs are performed only by the manufacturer.

The DPL is made in the USA, and Build America, Buy America (BABA) compliant models are available. Compliance depends on the model configuration, so request confirmation for your specific part number when you ask for a quote. Note that the OEM ..K000 version carries no CE mark.

Only for the compact-electronics versions (..C30R, ..C34P). State the direction as seen facing the meter, such as vertical bottom to top or horizontal left to right, with the part number. Orders for these versions that arrive without a flow direction may be delayed until it is confirmed.