BURKERT Type 8745 (SKU 20129652) is a mass flow controller (MFC) suitable for controlling the mass flow of large gas quantities. This specific model is configured for air with a nominal flow rate of 450 Nl/min and features a G 1/4" internal thread connection. It utilizes a direct-acting electromagnetic proportional valve (Type 2875) as the actuator, guaranteeing high response sensitivity and accuracy. The thermal inline sensor located directly in the main gas stream achieves very fast response times with minimal pressure loss.

General Technical Data

Property	Value
Operating medium	Air (Neutral, pure gases)
Nominal flow rate	450 Nl/min
Operating voltage	24 V DC (±10% voltage tolerance, ±2% residual ripple)
Port connection	G 1/4" Internal thread
Analogue interface	4...20 mA (Input/Output)
Maximum pressure	3 bar
Seal material	FKM (Fluor rubber)
Body material	Stainless steel 1.4404/316L
Wetted parts (sensor)	Stainless steel 1.4404/316L, Al₂O₃, PPS GF40, epoxy resin, silicon, silicon nitride
Medium temperature	-10 °C...+70 °C
Ambient temperature	-10 °C...+50 °C
Degree of protection	IP20

Variant with Electromagnetic Proportional Valve

This MFC variant uses a direct-acting proportional valve of the 2875 series. These electromagnetic proportional valves are normally closed and stand for highest measuring accuracy and repeatability with settling times of a few hundred milliseconds.

Performance Data	Specification
Valve position	Normally closed
Measuring accuracy	±1.5% MV, ±0.3% FS (under calibration conditions and after <1 min warm-up time)
Repeatability	±0.1% FS
Turndown ratio	1:50
Settling time (t95)	<500 ms
LED display	RGB-LED based on NAMUR NE107

Dimensions

Small nominal flow rates, with internal thread

Thread (A)	Thread depth [mm]
G 1/4	12
NPT 1/4	11
G 3/8	12
NPT 3/8	11
G 1/2	15
NPT 1/2	14
G 3/4	16
NPT 3/4	15

MFC with valve Type 2875

Variant with base block 00 or A1 for small nominal flow rates. Note: Dimensions in mm

Product Connections (Analogue)

Pin	Assignment
1	Digital input
2	GND (for supply voltage and digital input)
3	24 V
4	Relay, normally closed contact
5	Relay, reference contact
6	Set-point value input +
7	Set-point value input GND
8	Actual value output
9	Actual value output GND
Housing	Shielding

Measurement Principle

This sensor works as a hot-film anemometer in the so-called CTA operational mode (Constant Temperature Anemometer). Two resistors with a precisely specified temperature coefficient located directly in the media flow and three further resistors are connected to form a measuring bridge. The first resistor in the gas flow measures the fluid temperature, while the second, low-value resistor is always heated just enough to keep it at a fixed, specified excess temperature with respect to the fluid temperature. The heating current required for this is a measure of the heat dissipation and represents the primary measured variable.

Adequate flow conditioning within the MFC and calibration with high-quality flow standards ensure that the amount of gas flowing through per time unit can be derived from the primary signal with a high degree of accuracy.

Safety Information

Electrostatically sensitive components and assemblies: The device contains electronic components that are susceptible to the effects of electrostatic discharging (ESD). Meet the requirements specified by EN 61340-5-1 to minimize or avoid the possibility of damage caused by a sudden electrostatic discharge.

Medium under pressure: Medium under pressure can seriously injure people. In the event of overpressure or pressure surges, the device or lines can burst. Before working on the device or system, switch off the pressure. Vent or empty the lines.