What Is the KME Inline Thermal Flow Meter?
The KME is a modular inline thermal mass flow meter for compressed air and technical gases. The transmitter mounts in a gauge mounting block and can be removed without disassembling the pipework. It covers ½" to 2" pipe (DN15 to DN50), is rated to 232 psi (16 bar), and measures standard volume flow, mass flow, flow velocity and gas temperature.
The KME is designed for long-term and short-term installations. Its thermal measuring principle and hot film sensor element are designed for long-term stability and fast response (t90 under 2 s). A multi-point factory adjustment at 102 psi (7 bar) absolute is designed to provide accurate measurement even in the lower measuring range, which supports leak detection and related energy savings.
How the KME Measures Gas Flow
The KME operates on the thermal mass flow principle and measures volume flow at standard conditions, factory set to 14.7 psi (1013.25 mbar) and 32°F (0°C) per DIN 1343 and configurable by the user. Accuracy is quasi-independent of process pressure, so for normal requirements no additional pressure or temperature compensation is required.
Pipe Sizes, Measuring Ranges and Accuracy
One transmitter serves three pipe diameters, and two versions cover six sizes: KME-715/-720/-725 for ½", ¾" and 1" (DN15, DN20, DN25) and KME-732/-740/-750 for 1¼", 1½" and 2" (DN32, DN40, DN50). The pipe diameter setting must match the mounting block.
Measuring ranges in air:
- ½" (DN15): 0.12 to 44.88 SCFM (0.2 to 76.3 Nm³/h)
- ¾" (DN20): 0.24 to 79.77 SCFM (0.4 to 135.6 Nm³/h)
- 1" (DN25): 0.36 to 124.71 SCFM (0.6 to 212 Nm³/h)
- 1¼" (DN32): 0.52 to 202.06 SCFM (0.9 to 347.4 Nm³/h)
- 1½" (DN40): 0.81 to 315.71 SCFM (1.4 to 542.8 Nm³/h)
- 2" (DN50): 1.22 to 493.35 SCFM (2.2 to 848.2 Nm³/h)
Accuracy in air at 102 psi (7 bar) absolute and 73°F (23°C) is ±3% of reading plus ±0.3% of full scale. Gas temperature is measured over -4 to 140°F (-20 to 60°C).
Compatible Gases, Operating Limits and Materials
The KME is rated for compressed air, nitrogen, CO2 and argon and is intended for non-corrosive, non-flammable gases; consult us at the factory before using it in wet or dirty gases. Maximum operating pressure is 232 psi (16 bar), PN16. Medium and storage temperature is -4 to 140°F (-20 to 60°C), and humidity is 0 to 100% rH, non-condensing.
Ambient temperature is 32 to 122°F (0 to 50°C) with the display and -4 to 140°F (-20 to 60°C) without it. The housing is polycarbonate, rated IP65. The sensor tube is stainless steel 1.4404, the sensor head and element are stainless steel 1.4404 and glass, and the mounting block is anodized aluminum.
Outputs, Power, Display and Totalizer
The KME has two configurable signal outputs on a 4-pin M12x1 plug. Output 1 is a scalable 0-20 mA or 4-20 mA analog output (load below 500 Ω) or a switching output; Output 2 is a pulse or switching output. Power supply is 18-30 VDC at up to 120 mA (2.5 W) with display or 60 mA (1.6 W) without.
Switching outputs are DC PNP, maximum 100 mA, voltage drop below 2.5 V, configurable as N/C or N/O with hysteresis or window mode. EMC conforms to EN 61326-1 (industrial environment) and EN 61326-2-3.
An optional LCD shows current measured values and overall consumption, with push-button setup and menu guidance, and rotates in 90° increments. Without the display, the KME is configured over USB with the free KME-AFK configuration software (see the downloads on this page). An integrated consumption meter stores the total every minute and retains it if the supply voltage is interrupted, and a low flow cut-off suppresses flow below a user-set threshold.
Installation Requirements
The gauge mounting block has BSP (Rp, EN 10226) or NPT internal threads; the 1¼" (DN32) block is BSP only. The block is symmetrical and installs irrespective of flow direction, but the arrow on the transmitter must match the flow direction or an additional error of ±3% of reading can result. Depressurize the pipeline before mounting or removing the transmitter.
Allow 5.9" (150 mm) of clearance around the block, and tighten the transmitter mounting screws to a maximum of 4.4 lbf·ft (6 Nm) with the included 4 mm hex key. With the transmitter removed, the included sealing plug closes the block so the gas network keeps operating.
In compressed air networks, install the KME after the air dryer, or after the condensate separator and appropriate filters where there is no dryer. Air purity should meet ISO 8573-1:2010, at least Class 3.4.4, with non-condensing medium and ambient conditions. Mount vertically, or horizontally with the transmitter at the top or on its side; transmitter at the bottom is not recommended. Locate the meter before valves, as far as possible from flow disturbances, observing minimum inlet and outlet runs.
Common Questions about KME - Compact Inline Flow Meter
A hot film sensor element in a stainless steel sensing head uses the thermal mass flow measurement principle. The reading is volume flow at standard conditions (DIN 1343, factory set and adjustable), and the transmitter also calculates mass flow in kg/h or kg/min and standard flow velocity in Nm/s, and reports gas temperature to within ±1.26°F (±0.7°C).
An example code is KME-715R0L1NQ2: mounting block material (7 = aluminum), pipe size (15 to 50), thread (R = BSP, N = NPT), display (0 = none, 1 = with display), gas type (L = air, N = nitrogen, C = CO2, A = argon), units (1 = SI, 2 = US), each output's measurand, and the output combination.
Ordering option 4, the standard, pairs a 4-20 mA analog output with a counting pulse output. Option 3 uses 0-20 mA with pulse, option 2 switching with pulse, option 1 two switching outputs, and options 7 and 8 pair 0-20 mA or 4-20 mA with one switching output. Every output remains reconfigurable by the user afterward.
Not normally. The meter leaves the factory adjusted at an absolute pressure of 102 psi (7 bar); the pressure coefficient is +0.5% of reading per bar (14.5 psi) away from that pressure, and entering the actual system pressure in the menu or software corrects the error. The temperature coefficient is ±0.25% of reading per °C away from 73°F (23°C).
Minimum inlet runs: 15 × DN after an expansion or reduction, 20 × DN after a 90° elbow, 25 × DN after two elbows in one plane, 30 × DN after two elbows in two planes or a T-piece, and 50 × DN after a valve or slider. Outlet run is 5 × DN; light gases need longer inlet runs.
For a ½" (DN15) unit the analog output is scaled 0 to 75 Nm³/h, the switch point is 50 Nm³/h with 5 Nm³/h hysteresis, and the low flow shutdown is 0.15 Nm³/h. Pulse defaults are 0.1 s duration and 1 m³ per pulse, with measured value averaging set to 10. Each pipe size has its own table in the manual.
Pulse duration can be set from 0.02 to 2 seconds and pulse value from 3.5 to 35,315 ft³ (0.1 to 1,000 m³). The pause between pulses must be at least twice the pulse duration, and the minimum time between two pulses is 2 s. The manual gives a formula tying the minimum pulse value to the maximum expected flow.
Yes. The analog output averages between 1 and 50 measured values, each taken at a 0.1 second measuring rate. The specified t90 response time of under 2 seconds applies with averaging below 10 values; at the maximum setting of 50 values the response time rises to 5 seconds. The averaging value is set in the display menu or software.
A flashing green LED alone means no error. Code 1 (EEPROM fault) loses the totalizer and min/max values but keeps all outputs working. Code 2 is a display fault with outputs working normally. Code 4 is a sensing head fault: display values freeze at their lowest value and the analog output goes to 21 mA. All three need factory service.
Ordering numbers cover an M12 female connector for self assembly in plastic (ZUB-KAB-12 D500) or Quikon (ZUB-KAB-12 Q000), 2 m and 5 m PUR connecting cables (ZUB-KAB-12 K002), and spare sealing plugs for the gauge mounting block (ERS-KME-DS38). The plug needs no additional seal and is tightened to at least 20.7 lbf·ft (28 Nm).