CMOSens SFC6000D / SFM6000D Mass Flow Controller / Meter for Gases

www.sensirion.com/sfc6000

Jan 2023 – v. 0.1

4/12

1.1 Gas calibration

SFC6000D and SFM60000D are factory-calibrated for

multiple gasses. Table 1 lists the available calibrations

and the calibration gas numbers saved in internal

memory of the device. The desired calibration can be

selected by the user. Please see the application notes

describing RS485 interface, quick start guide or the

Evaluation Kit documentation for instructions on how to

activate a desired calibration. These can be found on

www.sensirion.com/sfc6000.

Please note that the maximum flow rate achievable

with each MFC is strongly dependent on the gas

measured. Table 1 lists the maximum flow rates for all

gasses for which the products have been calibrated.

The calibration for Air and N2 is identical. It can be used

with both gasses with the same result.

1.2 Accuracy

Accuracy describes how precisely the mass flow

controller / meter is able to control / measure flow rate

with respect to the real flow of a given gas. Accuracy is

mostly determined by the quality of the calibration and

can be different for each calibration gas.

For example: with mass flow controller set point of 10

slm and a real flow rate measured by an external

reference of 10.2 slm, the set point accuracy would be

calculated as:

������������������������������������������������ =

10.2 − 10

10.2

= 2.0% set point

1.3 Repeatability

Unlike accuracy, repeatability is not influenced by

calibration quality and is directly related to the build

quality of the mass flow controller / meter. It describes

how reliably mass flow controller is able to reach a

given setpoint (applied repeatably). For mass flow

meter, it describes, how reliably the instrument

measures the same flow repeatably.

For example: if a mass flow meter measures real flow

of 10 slm multiple times and the resulting flow

measurement results follow a Gaussian distribution

centered around 9.97 slm with 0.02 standard deviation,

then the repeatability is calculated as:

������������������������������������������������������������������������������ =

0.02

9.97

= 0.2% set point

Generally, for mass flow controllers / meters

repeatability is better than accuracy. For mass flow

controllers, in applications where an additional

calibration or feedback loop exists, it is possible to

relay on repeatability rather than accuracy of mass flow

controller. One example would be an optimized

process, where the setpoint value of mass flow

controller is fine-tuned to give the desired outcome. In

such case, it is not important that the actual flow is

close to the absolute set point – instead it is important

that the optimized set point can be achieved

repeatably.

Accuracy and repeatability of SFC6000D and

SFM600D devices are limited by set point error at high

flows and by the full scale error at low flows. Figure 3

demonstrates this.

1.4 Settling time

The CMOSens

 SFC6000 mass flow controller has

an ultra-fast settling time. Figure 4 shows the typical

response time of the SFC6000 in comparison to a

mass flow controller using conventional capillary

technology.

Figure 4

: Settling time of the SFC6000 vs. typical thermal

mass flow controller.

Figure 3

: Accuracy and repeatability at different set points.

s.p. = set point.